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Steve's Britannia
Tools, Jigs and other bits
This section is for the various bits of tools and fixtures that I have made to help me build Britannia. There is nothing particularly clever or innovative in any of the following items and all will have been made before by someone else. If I have been directly influenced by someone elses design I have acknowledged that person but, just because something I have made looks like something that has been seen elsewhere, if I haven't seen it then I haven't copied it and cannot offer a credit for it. At the end of the day, there is nothing original to be found in day-to-day engineering, it's all been done before one way or another.
  Screwcutting Indicator Dial  
I've had this lathe since 1985 and the only screwcutting that I've done on it had threadcounts that were a multiple of four. That is because it doesn't have a threading indicator dial and I've never really needed one before, having access to other machines. I now need to cut some 6 TPI threads and need an indicator to fit my 4 TPI leadscrew but, as the lathe is eighty years old, finding one would have been difficult, to say he least. They are not hard to make, though, so I knocked on up over the weekend. The first thing I had to make was the gear that engages the leadscrew and, on the basis that one makes a gear with four times the number of teeth as the leadscrew pitch, that was a 16 TPI gear with 1/8" wide teeth cut on a blank a little over 1.1/4" diameter. However, 1.1/4" will do, this doesn't need to be particularly precise. A bronze blank was machined up with 5/16" wide for the teeth and a 5/8" x 5/16" wide boss for fixing onto a 3/8" diameter shaft. Because I don't have a dividing head, I checked my lathe changewheels for one that was a multiple of 16 to make up an indexer and found this 32 tooth wheel.
With the gear blank made, I had to knock up a mandrel to hold both the blank and the changewheel so that I could index the thing round. I managed to cobble together a somewhat Heath-Robinson setup with a vee-block held in the vice and a detent mechanism bolted onto an old milling fixture. It looks very ramshackle but it's suprisingly sturdy and accurate. The cutting tool is a broken centre-drill which I've ground to form a 1/8" wide cutter, which is clamped into an offcut of 5/8" diameter bar and held in a collet.
I decided to try and combine my saddle/carriage stop and this thread indicator into a single unit so had to modify the carriage stop by milling away a section at the top. A 3/8" diameter hole was drilled and reamed through and the unit refitted to the lathe using the single bolt. The gear was fitted to a length of 3/8" diameter bar and offered up to the leadscrew to check both size and fit, as well as orientation of the stop block. The rotating barrel with the five adjustable stops have been temporarily removed. Next up was the indicator dial which was made from a piece of 1.1/8" diameter brass with an angled face and parted off about 5/16" wide. The hole through was drilled and reamed 3/8" diameter, and a cross-hole drilled and tapped to take an M4 grubscrew. It was then clamped to a short length of bar, held an a square collet block and loaded to the tilt-and-turn vice to mill four indicator grooves. I don't have any engraving tools so a 1/4" centre-drill was ground to a fine point instead, the four lines being "engraved" by indexing the block in the vice. <
The stop block was reassembled, a collar made for the gear spindle to stop it climbing up the block and the indicator stamped with four numbers. Although it is barely visible, I also used an end mill to create a small pocket at the top of the block to take an "O" ring. The dial rests on this and keeps the crud out plus adds a little bit of friction to the spindle. Finally, the whole thing was fixed back onto the saddle and adjusted for fit. When not in use, The stop block can be slightly rotated to disengage the gear but without making the stop go out of line. There are sixteen positions where I can engage the screwcutting lever but I will use just the four marked positions, which will enure that all whole-number threads can be cut without creating the dreaded two-start thread. Another worthwhile additon to the lathe and it cost precisely nothing because all materials were sourced from the scrap-box.
  New Lathe Cross-slide  
The cross-slide on my lathe, a clone of the Denham Junior, doesn't really provide a means of mounting a vertical slide because the whole thing is too tall, although the circular tee-slot does provide direct mounting and swivelling for the compound slide. The one advantage the lathe does have, however, is the ability to remove the whole slide very quickly by undoing two coverplate screws and two leadscrew fixing screws. Needing to machine the saddle of the chimney for my loco, I decided to make a new cross-slide for my machine which would allow for direct fixing of alternative tooling and a vertical slide. The dovetail section is 1/2" high so I reckoned that the table needed to finish at 6" long by 5" wide by 1.1/4" deep.
I started with a lump of cast iron cut to just over the above dimensions. After setting up in the 4-jaw chuck on the lathe, the two faces were cleaned up and finished about ten thou oversize, them the edges were squared and finished to size in the mill. I don't have a vice large enough to mount this workpiece flat so all subsequent operations were done with the work mounted directly to the mill table. First of these was roughing out the underside, followed by milling the slots for three tee-channels with a 10mm carbide end mill. Having a table feed was an absolute godsend as this took quite a few hours of cutting.
Next, a 12mm diameter tee-slot cutter was passed up and down each channel, setting over to 1.1mm for the first pass and 2mm for the second, finishing with a 16mm wide slot. I have deliberately made the slot-spacing assymetrical to allow for a wider range of clamping solutions. Next I drilled and tapped a large quantity of M8 boltholes, again using different patterns for greater options. Clamping the work to machine the dovetail was always going to be problematic because it's neary as wide as my mill table. The power of the cut will be a bit too heavy for cam-button clamps. I got round this by modifting four clamps so that the tongues would fit into the tee-slots, then turning a length of angle iron into an extension of the table by bolting it to the front where the stop collars fit. I did have to dismantle the table feed operating arm to get it to fit but I was still able to use the feed by operating the lever between the microswitches.
This is the cross-slide mounted on the table and the dovetail cutter ready to do it's work. It's a left-hand cutter so I have to run the machine in reverse and cut left-to-right. A friend lent me the cutter for which I've had to make a mandrel because I couldn't use his 2MT mandrel. I made one with a 16mm diameter stem to hold in a collet; my mill has an R8 spindle. Before setting up to mill the dovetail, I trammed the head. These mills are notorious for going out of alignment after heavy use in the same direction because there is no locking dowel to keep the head aligned at 90o to the table. I knew it needed doing because I was getting tail-cutting when sending the tool left-to-right. After cutting the dovetail, the workpiece was offered up to the lathe to check the clearance over the centre section and a 10 thou feeler fits in there quite nicely.
The jib strip was next and I made this from a piece of 1.1/4" diameter cast iron bar, milling it down to form a flat bar 3/4" wide by 1/2" high. I set up my angle table to exactly 30o by clocking out on an angle gauge. Next, a fence was clamped to the top, clocked square and the work fixed to the fence using a pair of engineer's clamps. The work needed to be on and off the fixture a number of times until a nice, sliding fit was obtained and this seemed the quickest and easiest way to mount the work.
The jib strip was faced to length, then a pair of recessed holed were drilled to take M5 cap screws and the jib strip lightly clamped the underside of the table. The centre of the five jib-adjusing grub screws was replaced with a long caphead screw to act as table lock. Also drilled and tapped were the two holes for the leadscrew block and the holes for the bedway cover. And, finally, a picture of the new table ready to carry some tools. It takes less than two minutes to undo this one and replace the original cross-slide so I expect to be swapping between the two on a regular basis.
Home-made Keyway Broach  
I've just spent ages trying to purchase a 1/8" keyway broach but could only find sets from DuMont or Steelman which require an extension to the overdraft or some single items from Australia which were attractive until the carriage charge was noticed. After getting back on my chair, I decided to try and make my own broach. First, the maths. I need to be able to cut the keyway to about 0.064" deep and would like to plane off one thou per tooth. Any more would probably require a press tool of some description and I only have my drilling machine available. Assuming three passes, I need about twenty teeth on the broach and would like to complete a pass in about four inches. I will use a 4mm carbide slot drill to cut the teeth in a length of 1/2" x 3/16" ground flat stock. I don't have 1/2" x 1/8" GFS and I'm not about to buy a piece in case it doesn't work. First job was to saw off a 7.1/2" length of GFS, load it to the mill table on some sacrificial packing and clock it true to the table. Then the cutter was offered up to the edge of the workpiece until touch-on and then moved in a further three millimeters and locked.
A suitable starting point was chosen about half an inch along the bar and the table locked and the first plunge cut made to create the front form of the first tooth. The table was then wound along six millimeters and the next hole plunged through. This was repeated until I had twenty one holes. Next, I had to relieve the back of the teeth leaving just the tiniest of flats showing on the tip. I started by repositioning the cutter to 2.5mm in from the face and 1mm nearer the starting end and then plunge-cut the back of the teeth, moving 6mm along each time. Then I set up my tiny angle plate with the work rest set at ten degrees. The work was clamped to the faceplate with the edge of a tooth in line with the end of the faceplate and a crosscut taken with the 4mm cutter. Then the work was moved to the next tooth position and the process repeated. The last operation on this edge was to relieve the leading and trailing edges by about five thou to prevent any form of binding after which the broach was removed from the vice.
Now it was time to reduce the thickness of the teeth to 1/8" and for this I mounted the work directly to the table, using the clamping bolts as a fence. I needed to move the work along after milling the first section because my total travel in the x-axis is only 75mm. Three passes each side at ten thou per pass saw the teeth reduced to the correct size. The last bit of milling was the front-to-back size of the broach. I needed about twenty thou difference between the first tooth and the last tooth and this was set up on parallels using feeler gauges to tip the workpiece. I'm aiming to get the major size to about 3/8". Much bigger and the guide bush will be practically cut in half but if I go too small there is more chance of distortion during hardening. Actual size is unimportant as I will make the guide bush and shims to suit.
I have also drilled a hole in the end because I want to hang the broach vertically whilst heating and also when plunging into the clean engine oil, again to reduce the risk of distortion. Before heating, I cleaned the whole thing up with slipstones, tied on the hanging wire and then degreased it. Then it was time to harden. First, I took the broach gently up to dull red and held it there to soak for a minute or two before carrying on up to cherry. Then it was a straight vertical plunge into the oil, keeping the thing moving gently for a few minutes while it cooled properly. At this point it was glass-hard and I took care not to drop it! It was gently stoned down the sides and back until bright all the way along and then I tempered to about mid-straw for approx 60RC. I could have done it more accurately (about 200 C) in the kitchen oven but senior management may well have objected.
All I need now is a guide bush and shims to fit Britannia's driving and coupled wheels and I'm ready to cut some keyways but I will cover this as an entry to the diary in a few weeks time. I have, however, made a collar from one of my sash weights and used this to test the broach and am happy to say it works a treat. And measuring the depth of this one allows me to correctly calculate the final shim thickness required for the wheels. And one other tip - if you use a plastic bottle like I did, stand it in another container. When I plunged the broach into the oil, I forgot to allow for the expansion of the oil due to heating and it promptly overflowed all over the bench. Then, to cap it all, I must have hit the bottom of the bottle and the heat in the broach was still enough to melt a small hole in the bottom so I now had leaks at both ends. I must have had a brain-fart when I set that up.
Combined Beam Compass & Drill Jig  
In order to get the bushes in the side rods for Britannia accurately placed, one needs to know the exact distance between centres of each of the axles so have I made a combination beam compass and drill jig to help keep things accurate. It's not the correct term but is sometimes called a trammel. The two arms are made from 25mm x 3mm flat bar one of which has had a 4mm slot milled into it and the other has three M4 x 0.8 holes tapped into it. I have set bushes into the adjustable arms with 1/8" reamed holes in them. The bushes are shouldered and on opposite sides so that the device always sits level on a surface. I have also made a pair of trammel points from 1/8" silver steel with a sixty degree inclusive angle to suit standard centre drills and have filed a notch on the centre-line at each end to aid alignment. The first use will be to set the trammel points across the leading and driving axles, lock the beam screws and transfer the holes to the front side rods using a 1/8" drill.
  Next item...  
   
  Fitting a DRO to the mill  
There are plenty of references across the various forums concerning fitting DROs to lathes and milling machines but the information tends to be a bit scattered and piecemeal so I have jotted these notes down covering the start-to-finish process of puchasing and fitting a 2-axis DRO with glass scales to a small milling machine. My own milling machine is an SP2217-III from SPG Tools but it is physically identical to the Warco WM-16, the Amadeal AMA25LV and the Chester 20V and all these machines have a 700mm x 180mm table. The first thing one needs to do is decide whether one wants a 2-axis or 3-axis measuring system and source the product accordingly. I only want 2-axis because my machine already has a small DRO on the quill, and this will suffice, so it is left to the reader to devise how they may fit the third axis if required. The next important thing to know is the size of the scale to use on each axis and a scale slightly longer than the overall travel of the table needs to be chosen. However, there is no point in choosing a scale that is much larger than the table travel because such a scale will probably overlap the ends of the table and be prone to accidental damage. Another thing that needs to be taken into account is that the scales come in various sizes in 50mm increments and the overall length of the glass scales is 140mm longer than the travel length.
In my case, the longitudinal travel (X-axis) of the table is 485mm and, therefore, a scale length of 500mm was chosen while the cross traverse (Y-axis) is 175mm and a 200mm scale was chosen. Remember, however, that the physical length of the scales are 640mm and 340mm respectively but it is 500mm and 200mm scales that one is ordering. There are many suppliers listed on a certain auction site and the price for a full kit of parts is about 180 delivered to the UK and one has to let the seller know what size scales one requires. I have issues with this auction site (my own personal hang-up) so I bought the self-same thing from one of these companies through Amazon and paid 192 for mine. As soon as I placed the order, I used the Amazon email service to contact the seller and advised them that I required scales of 500mm and 200mm and a reply was received next day confirming that these sizes would be dispatched. Just prior to delivery, I was contacted by the carrier with a request for a payment of 19.00 for the VAT that was due. All the sellers on both Amazon and the auction site state that VAT or duty may be payable on the goods as they originate outside the EU so was not unexpected. The order was received seven days after being placed and was immediately unpacked and checked for completeness, arriving as two separate packages. The first package contained the display unit and this is what was in the box.
The second package contained the scales with their read-heads. Be aware that they come with a small transit locking screw holding the read-head firm on the scale and which needs to be removed before attempting to move the read-head. Everything appeared to be in order although the instruction manual appears to be one of the worst translated documents I have ever seen and will probably be discarded. Common sense and an internet search will sort out most things rather that trying to decipher this gibberish. Containg my impatience to hook it all up and conduct a test, I sorted out the brackets and mounted the display unit in position to the right of the machine and then went off to find a spare computer lead to apply power because the one supplied was the European format. It all assembled easily although I have placed a couple of fibre washers between the wall bracket and the arm to fill the space and allow for easier adjustment of the display unit. After this, I removed the transit screws from the scales and plugged them in to their respective ports on the rear of the display unit which was then turned on. The unit automatically set both scales to zero and I slid the read-heads along both scales to check that they were working properly, also changing from metric to imperial units to check this function and all was fine. A word of caution. Don't be tempted to slide the read-heads up and down at high speed whilst connected and turned on. I don't know the reason why but have been advised that it is easy to damage the electronics if overspeeding occurs. These things are too expensive to find out if that is just a myth or not so I treated them with respect.
After offering up the scales to see how best to fit them, I then marked up their respective limits and centres of travel because the scales are not symetrical. I also centered the table and saddle, making loads of marks with a felt-tipped pen, and then removed the table and saddle as a single unit from the machine. I had decided that it would be too much hassle trying to drill and tap all the fixing holes with everything in situ. This involved removing all the paraphernalia from the front of the table, the jib strip with its front adjusting screw, the rubber bedway cover at the back and the Y-axis leadscrew and handle. Once these were removed, the saddle was slid as far forward as possible and the two screws that hold the leadscrew nut were loosened and the nut allowed to fall down so that the saddle would come off the knee completely. I chose to fit the Y-axis first as I thought that would be the most awkward and the first job was to mark out, drill and tap two M5 holes in the knee to allow the scale to be affixed. These were done freehand using a 3.0mm bit in a pistol drill to act as pilot followed by a 4.2 drill, taking care to keep things as square as possible and not too much force. Then I tapped them M5 freehand with a spiral-pointed tap because they are less likely to break than any other type and because they self-align as well.
I also made a couple of spacer bushes from some 1/2" brass but they needed dressing by hand at one end because of the shape of the casting. I suppose I could have spot-faced the M5 holes but I couldn't be bothered to gring a drill up for it. Next I had to make a bracket to couple the read-head to the saddle and a hunt through the scrap box produced a door-mounting coat hanger and this was promptly modified to suit. The table and sadlle were then upended on a workbench and the saddle marked out from the bracket and then drilled and tapped M5.
Tapping was proving to be a bit problematic because of access but eventually I managed it by using a small drill chuck. I didn't want to separate the table and saddle, too much work. After offering everything up to check that it would all work, it was time to fit the X-axis and I have fitted it to the rear of the table even though I have lost about 25mm of travel. I feel this is less important than losing the dead-stop adjusters and the slideway locks. Even the embedded rule on the front will be useful and mounting the glass scale on the front would have meant that all these facilities would be made redundant. This time the scale and read-head will be mounted with M4 screws and I was able to use the mill to drill the holes.
Unfortunately, I got a bit carried away and forgot to take pictures of the next couple of stages but basically everything was centered and holes were spotted through, drilled with the mill and tapped by hand. Finally, the mill saddle and knee were thoroughly cleaned and given a film of hydraulic oil prior to reassembly. The only awkward part is getting the leadscrew nut aligned before locking into place but even this was not too much effort. Then the scales and read-heads were fixed to the machine and carefully aligned, and the leads taken to the DRO. The pictures should be self-explanatory.
Vertical Slide for the Lathe  
I've been chewing over how best to finish the bores of my cylinders based on the limited equipment I have. The usual way that this is done is to mount them on a vertical slide on the lathe and use a between-centres boring bar. A good example is the Myfords vertical slide which bolts directly to the cross-slide giving that required third axis adjustment. However, I don't have one, and it looks like it would be awkward to mount one anyway. To help visualise the space and to see what I could come up with, I started to strip the compound slide off of the lathe and that's when I realised I did have a vertical slide, I was just looking in the wrong place for it!
I was holding it, all I needed was find a way to mount it vertically on the cross-slide. None of my angle plates were any good for the task so I cast around for something to use and eventually converted a lump of 100mm x 50mm steel box section into a mounting box. The walls are a bit thin but, by retaining the box section, the overall lump is quite sturdy and when the compound slide was mounted to it, the whole setup was quite rigid. I've made it slightly overhanging so that I can use the full travel of the slide but the fixed part of the slide sits on the cross-slide to enhance rigidity. And there I have my vertical slide! It can be mounted as shown or swung to face the chuck and still retain the full travel but can also be mounted at any angle with limited travel.
At some point in the future, I will make or buy a tee-slotted table to mount on the slide but, for now, I have made a mounting plate which bolts to the top of the slide. This is needed because the cylinder blocks are bigger than the top mounting face of the slide and there would be no means of securing the cylinder to it. Because I wasn't sure whether I would be able to get the requisite adjustment, I have made the plate with the clamping bolt holes offset from the centre-line so that I can turn it up the other way if neccessary. And so it proved, the first way up I chose fouled the saddle so the plate was reversed. Two of the photos show me checking to make sure I can machine both bores without having to unbolt the cylinder.
Once I knew that this part would work, I then made a clamping arrangement to hold it all firm. Although this all looks a bit Heath-Robinson the important thing is that it has cost me nothing, all the bits of plate and bar are from the scrap box and the clamp bolts are from the mill clamping set. Now it's just a case of swinging it round, clocking each cylinder true in all planes and machining the bores. But before I do any of that, I need to make a between-centres boring bar first.
Between-centres Boring Bar  
It seems easy enough to be able to load locomotive cylinders (or anything with a long bore) to a four-jaw chuck or a face plate and machine the bores using a boring bar in the lathe tool post. The problem that I see with this method is it can introduce a taper to the bore of the cylinder because of misalignment of the headstock or twisting of the bedway and the only way to ensure a parallel bore is to use a reamer or similar tool in the tailstock to size the bore, quite an expensive solution in the larger sizes and still no guarantee of a parallel bore if the reamer is out of line and cuts at the back. Another problem is that the valve bore is way off the centre of mass of the casting and swinging this lump around in a four-jaw chuck would have the lathe oscillating like a rocking chair. It could be mounted on a large faceplate with a balancing weight but, since I don't have one, that option is not open to me. Cylinder bores could be machined successfully using a boring head in a vertical mill but it seems that the majority of our hobby-sized machines, my own included, do not have enough travel in the quill to complete the operation. Winding the table up and down (z-axis) on a turret mill, where the milling head remains static and the knee moves, would work well enough but on our smaller hobby mills adjustment is often made by winding the head up and down the column and this introduces it's own set of problems. In fact, it is impossible in round-column mills to stop side-to-side movement and even dovetailed vertical columns need to be quite closely adjusted on the gib strips to prevent any wander.
When it comes to parallel bores, between-centres boring in the lathe cannot be beaten. In fact, if you think about it, it is impossible to introduce a taper to the bore, other than for tool wear in a single pass. The reason for this is because it is a single-point cutter and the tip of the cutting tool is following a fixed circular path which will not deviate (unless the operator changes something, such as tightening the tailstock centre during the cut which may cause the bar to move sideways). The only inaccuracy that can occur is in the alignment of the bore or size of the bore, both of which are the responsibility of the operator during initial setup. However, a parallel bore is guaranteed! It is called between-centres boring but, in fact, the boring bar doesn't actually need to be between centres. The only requirement is that both ends of the tool need to be supported to ensure that there is no lateral movement. The advantage of using the bar between centres is repeatability because, once the size is set, it can then be removed from the machine and the next workpiece set up. Then the boring bar can be reloaded and machining of the next item continue. It is usual, therefore, to use a centre in the headstock and drive the bar using a driving dog fixed to the bar and driven by a catch-plate. However, to ensure good repeatability, it is normally neccessary to lock the tailstock in place and adjust the pressure to the same setting each time.
If there is only one workpiece that needs machining, then it is possible to hold the driven end directly in a three-jaw chuck and with a live centre in the tailstock supporting the other end. It doesn't even need to be running perfectly true at either end because this is not what controls the diameter of the cut, it just needs to be held rigid so that the tip of the cutter rotates around a fixed circle in space. All adjustment of size is made by varying the height of the tool tip above the centreline of the boring bar. Measuring the bore, however, is a different matter and this is where being able to remove the boring bar and return it accurately pays off. If the bar is designed well enough, then it shouldn't need to be removed from the machine as it would be possible to use digital or vernier calipers to measure one end of the bore. There is no need to measure both ends because the bore WILL be parallel. However, if greater accuracy is required then removal of the boring bar would be an asset so that a bore gauge or plug gauge could be used instead. This first boring bar that I have made is designed to finish the valve bore at 1.1/4" diameter and is made from 25mm diameter mild steel and is a little longer than twice the length of the cylinder. The tailstock end has been centre-drilled with a No3 Slocombe and I intend to hold the bar in the 3-jaw chuck so have turned a shoulder to rest against the chuck jaws. The cutter is an old No.3 centre drill suitably ground and can be adjusted to produce a bore in the range 1.1/16" to about 1.1/2". Adjustment is with an M6 grub screw beneath the cutter and side-locking is provided by an M5 grub screw.
Modifying a pair of Drill Press Vices  
Having a need to hold some long flat bar on the mill, I purchased a pair of drill press vices from Toolstation for the princely sum of 12.90 each. They are pretty rough and ready, definitely not square or level but they are made of cast iron so I decided to re-machine them as a matched pair for general purpose milling jobs. I first spent ten minutes or so on each one flatting the bases on some wet and dry on my surface table and then dismantled them to leave the main casting. The jaw facings that have been provided are just strips of some unknown gash material as are the sliding jaw catch plates. These are going straight in the bin, along with the screws.
I trued them up as best I could on the mill and machined the slideways first, the difference in heights being seen by the size of the chips on each one. Then I put the large angle plate up and milled for a clean-up on the two sides followed by squaring up and milling the front and back. This gives me the option of aligning the vices using a square or butting up to my tee-slot packers if I don't need super accuracy. In hindsight, it would have been smart to do this set of operations first. While I had the angle plate set up, I also drilled and tapped an M5 hole in each end of the fixed jaw section to allow work-stops to be bolted on at either side.
Next, I trued each vice body in turn and milled the fixed-jaw face for a complete clean-up and also made the lower step where the jaws sit exactly the same height as the slideway. The picture shows just how rough the original machining is! I was also going to give the insides of the slideways a quick lick to square them up but I didn't have enough travel to do them in this setup. In the end, I didn't bother, it's the least important part of the whole job.Once the machining of the upper surfaces was complete, I then machined the underside of the slideway. This needs to be dead parallel to the upper surface of the slideway so that the jaw catchplate rides smoothly along the underside while the sliding jaw moves along the bedway without jamming. The more accurate this part is, the less jaw lift there will be during tightening.
Now it was time to machine the sliding jaw castings. To start, I bolted the existing jaw faces to my small angle plate and machined the top to get them square to the jaw faces. These were then clamped to the mill table and the two sliding surfaces machined followed by re-positioning the clamping arrangement and milling the catchplate mounting to size. I have left these a couple of thou proud of the size of the vice body as mentioned above and will lap these down later to suit each vice.The jaw-mounting faces were the last to be machined, the castings being mounted in a small vice and skimmed to clean up. Then it was time to deburr all round and give each of the machined faces a bit of a rub on some wet and dry before offering each jaw to the main casting and checking for a nice sliding fit.
It was at this point that it became obvious that the clamping-screw hole in the sliding jaw was about forty thou lower than before and would need bushing and each jaw was mounted back on the mill, the hole clocked out and then the table moved to the offset position. A 5/8" dia slot drill was then plunged down to the original depth. Meanwhile, on the lathe, a pair of brass bushes were made from 5/8" dia bar, drilled 3/8" and parted off. These were then loctited into the sliding jaws and left to set, followed by drilling through the existing retaining screw holes and tapping M5. The ends of the clamping screws were also in poor order so I cut off the front section completely and then remachined them with flat ends and the retaining undercut in the correct place.
Finally, a length of 3/4" x 3/16" ground flat stock was cut up to provide two sets of hard jaws and two underside catchplates. The holes in the jaws have the same side-to-side spacing as before but had to be compensated for in the vertical plane to allow for the material removed during milling and are held in place with M5 countersunk screws. To see how much jaw lift I had, I nipped up a thin parallel in each vice in turn, set a clock on the moving jaw and then tightened up fully. Originally the deflection was in the region of three to five thou on each but after a few sessions back and forth on the surface plate, I've got that down to about a thou. On one, I went a tad too far and the jaw locked up but a polish of the slideway underside freed it off. The final picture shows them being used as a matched pair for the first time.
Power Feed for the Milling Machine  
After sitting at the end of the mill winding the handle for a very long time facing up a 12" length of black, flat steel I decided that a table feed was an essential extra. Although there are feed boxes available for my type of mill, they are around 300 each and as rare as hen's teeth and, unless I'm missing the obvious, don't have automatic disengagement. After spending a couple of days trawling the internet and watching endless youtube videos, I decided to make my own based around a windscreen wiper motor. As made, this project will work directly with a Warco WM-16, Chester 20V, Amadeal AMA25LV and SPG SP2217-III which all use the same 700mm x 180mm table, and is easily adaptable to mills of other sizes. Total cost of bought-in parts was under 30, everything else came from the scrap box. To make a useful power feed five things are needed; a motor, a way to mount it, a power supply, some sort of speed control and a means to engage and disengage the drive. The first item on the list was purchased from the local car breakers and cost 8. Although it doesn't seem to matter what vehicle it comes from, front wiper motors are larger than rear wiper motors, probably because they drive two blades. I'm told that mine came from an Audi A6.
On getting it back to the workshop, I hooked it up to my battery charger and tested it in both directions by swapping the polarity: it worked fine and the current draw was 2A under no-load conditions. This will probably rise to somewhere between six and ten amps when driving the table, especially if the table locks are lightly nipped up, and a power supply will be chosen or built once this figure is known. Meanwhile, a car battery and ammeter will suffice to get started. The next thing to buy or make is a pulse width modulator (PWM) whose job it is to act like a dimmer switch and slow down the feed rate. This is just a simple device which generates a square-wave signal with adjustable mark-space ratio and applies this to one or more power transistors that provide power to the motor. These are easily made using the long-standing NE555 timer chip but I found some ready-built ones on Amazon for 2.83 with free postage so two were ordered. They are not worth building at this price!
Before designing the motor mounting, I had to choose what sort of clutch arrangement I wanted and decided to use a sliding drive-dog layout that could be automatically disengaged by the machine using stops. The advantage of this is that if my attention gets diverted for any reason while a cut is running, the stops will ensure there is no disaster. After much internet research, and not finding exactly what I wanted, I decided to design my own system using a sliding brass sleeve arrangement that would work in both directions with a centre-off position. The framework for the motor and clutch would be mounted at the left-hand end of the table and the operating controls at the right-hand end where I always stand to wind the "X" axis handle. To get started, I removed the M8 nut and washer holding the right-hand handle followed by the handle itself. This revealed a key set into the shaft which was also removed and put away safely with the other parts. The next item on the shaft is a thrust bearing and this needs to be retained in place and a way found to adjust the pressure on it. This function was previously undertaken by the Nylock nut on the end of the shaft.
Measuring the shaft showed it to be 10mm dia and a sleeve was designed to fit this and become both the bearing adjuster and the drive mechanism for the table. It is a 40mm length of 1/2" hexagon mild steel which is drilled and reamed 10mm to a depth of 20mm and the balance drilled and tapped M8. The sleeve is screwed onto the shaft and adjusted until it just locks the table, then backed off a tiny amount and a grub screw fitted in the end of the sleeve acts as a locking device. The wiper motor has a knurled and angled face with an M8 threaded section so this was dissassembled and put in the lathe so that a 10mm dia spigot could be machined on it. For this, the sleeve is 25mm long with a 10mm dia hole reamed to a depth of 10mm and the rest tapped M8. There is also an 8mm wide undercut on the O/D machined to the root of the hexagon and the reason for this will become obvious later. The grub screw in the end is still needed to ensure that the sleeve doesn't unscrew itself from the shaft when going in reverse.
The motor mounting was now started and the main requirement was to get the ends of the two shafts in line and about half a millimeter apart, the idea being that a sliding collar can connect the two. After working out the PCD for the motor mounting holes, a piece of aluminium plate was sawn and then drilled to suit followed by the bolting on of the motor. This assembly was then offered up to get some idea of spacings. It obviously needed some way of being connected to the table and this meant that some fixing holes had to be placed in the table end-plate. A piece of 25mm x 3mm steel angle was chosen as the starting point and a 150mm length was drilled with a pair of 5mm clearance bolt holes and a relief section milled away to clear the leadscrew boss on the end-plate. The end-plate itself, which is made of cast iron, was drilled and tapped with two M5 holes in corresponding positions.
At this point, I decided to discard the first motor mounting plate and, instead, made a frame from some more of the steel angle. Hole positions for joining the pieces together were first calculated and these were drilled M5 clearance or drilled and tapped M5. The end piece also had a pair of M6 clearance holes drilled to mount the motor. Everything was assembled and it was obvious that some adjustment in all three planes was neccessary and most of the clearance holes were made into slots instead.
Now it became relatively easy to adjust everything and get the two hexagons exactly in line. The only downside at the moment is that the motor has to be mounted as shown in the next picture but I believe there are other motors that are the opposite hand, which would place the motor rearwards, and I may try and find one. Now I needed to make the hexagon sleeve and a piece of 1" diameter brass was faced to 48mm length and then set up vertically on the mill table. Using the bolt hole circle formulae from the Zeus book, and allowing for the size of the drill, a series of six holes were drilled through the block using a long-series 2.5mm drill. These form the points of the hexagon.
The block was then returned to the lathe and the centre was removed using a 1/2" drill that I reground to have a 90 degree point angle. This was to ensure that the drill followed the centre of the workpiece and didn't get deflected by the six corner holes. At the same time, a 1/4" wide undercut was made in the bore 1/4" in from the front and to just below root diameter. A piece of the hexagon bar was cut about 2" long and a 1/2" dia spigot put on the front, the idea being to use this as a broach in the vice. It worked - just - but wasn't very good and the hole was cleaned up with files instead. The broach came in handy as a gauge, though.
Everything was now assembled, with the motor mount adjusted until the hexagon sleeve slid smoothly along the drive and driven shafts and the PWM was wired up to provide variable speed. As there was no mechanical means of moving the sleeve at this stage, it was engaged by hand. Everything worked as expected and I was able to control the feed from a dead stop to the equivalent of a fast turn by hand. Making all the mechanical linkages was straightforward and the only new holes on the milling machine have been confined to the table endplates. The first items to be made were the main actuating rod and the two brackets to hold it in place. This required a hole at the top of each endplate, which I have tapped M5, two pieces of the 25mm x 3mm steel angle cut to suit and a length of 6mm dia mild steel rod. A spare brake-rod eye has also been modified and fitted to the end of the actuating rod.
The next items I made were the operating lever and it's support bracket, which has been bolted onto the right-hand table endplate using a longer M6 Allen bolt in the existing hole. The bracket was another piece of 25mm x 3mm angle and the lever is made from an offcut of 1/2" x 3/16" flat mild steel which was turned down at one end and threaded to allow a plastic handle to be screwed on. It is fixed to the bracket with an M5 shouldered bolt and to the actuating rod eye with a clevis pin. To be able to auto-stop the feed, I then had to make a new block to replace the one on the front of the table. This was drilled to allow the actuating rod to pass through, and acts as a centre support as well. I have milled an angle on the top so that I can still use the table rule if required. A pair of stop collars were also made and loaded onto the actuating rod.
To be able to move the driving sleeve from side to side, a gear selector fork arrangemant was made using a piece of steel box section which has a 4mm wall thickness. A pair of pivots were made on the lathe from some 5/8" dia mild steel and these have had tongues milled onto the top to fit the groove that I have now put in driving sleeve. This was then bolted to a legth of 3/8" square mild steel which becomes the operating lever at this end. A bracket was now made to create the anchor point for this sub-assembly and was bolted to the front of the motor frame.
Then the operating lever was offered up and the approximate centre point marked to create the pivot point, followed by drilling and reaming 6mm. An M6 shoulder bolt was made and the whole lot was then assembled. This left only the coupling piece from the main actuating rod to the operating lever left to make and this was machined from another piece of 3/8" square mild steel. The bottom was turned to create a shoulder bolt once more, since this allows the operating lever to pivot, and the top was drilled 6mm dia and a cross hole drilled and tapped in the end. This allows adjustment of the relative positions of the two levers at final setup.
Although the electrics are still jury-rigged together at the moment, the whole lot was now tested for function and it threw up a small problem. In "neutral", for want of a better word, and with no power to the motor, the lever mechanism work really well. Applying power and engaging the feed also works as expected. The bugbear is in the disengagement of the feed. Under load, it is quite difficult to return the lever to the central position and it seems that the problem is in the amount of friction between the sleeve and the driving hexagon because slight forward pressure on the winding handle is enough to free it instantly. I have made the fit quite loose, polished everything up and applied lashings of grease but it still sticks so I will now look at reducing the contact area during engagement.
I have remade the bracket that supports the sliding sleeve fork and moved the pivot point nearer to the sleeve. This has gained me a 2:1 mechanical advantage and is a great improvement on the previous pivot point which was actually a 20% mechanical disadvantage, the pivot point being nearer the actuating rod than the sleeve. So far, it appears to be working quite well and the feed disengages at the stop point each time. However, a little more work is neccessary before I will feel fully confident of it. Last night, I made some bushes on the lathe while leaving the mill to clean the face of some black bar, about twenty minutes a pass so rather boring (and tiring) to just sit there winding the handle.
I have used it quite a bit lately and thing are loosening up nicely now. The feed disengages when a stop hits the centre support but I'm going to need to put some sort of spring bias on the lever because it jumps out of drive occasionally in one direction but the other way is fine - for now. I have added the microswitches that control motor direction and these function as expected. Moving the lever in the opposite direction reverses the motor and pressing the button makes it go flat out. However, it's more like a mobility scooter than a Porsche and I can wind it faster by hand. Still, it works. I was wondering where I could get a power supply to replace the battery charger and my Dremel power supply has been sitting practically on the end of my nose the whole time. 13.8 volts smoothed and regulated, and good for 5 amps which is more than I need. I thought this motor might need more but it doesn't. The other thing of note is that this windscreen wiper is a permanent magnet motor and is a great swarf attractor. So not such a smart choice after all. And I needed to get a new 10k pot from Maplins because this Chinese one on the speed controller gave up the ghost.
  Large Fixed Steady  
I now have my smokebox material and it's a rather large lump of metal which needs a few machining ops done on it. I am, however, a bit light on tooling and this presents a challenge. I need some support at the tailstock end but a large pipe centre won't solve all the problems. So I decided to have a go at making a decent-sized fixed steady for the lathe using whatever was in the scrap box. A fixed steady is usually a sturdy lump of cast iron but as long as one is not greedy with the cuts it doesn't need to be particularly strong and rigid. Pretty much all the effort is outwards from the radial forces but there is very little lateral force involved so this can simplify the design. I made mine from an old car disc brake and this is how I went about making it. There were no drawings involved with this, winging it with back-of-a-fag-packet sketches as I went along. The first job was to make the bedway clamp and for this a lump of 3" x 3/4" flat mild steel was sawn off 4" long. After finishing the size to fit between the leading arms of the saddle, I made the angled recess to locate on the rear way. I set up expecting to mill out the clearance slot first with a small end mill and follow this with a large 45-degree cutter.
However, the cutter was nowhere to be found so I had to change over to the angle vice and use a standard endmill instead. This is a 16mm one I bought for a quid at the Midlands show, so it's paid for itself already. Because of the large overhang, I had to do this with twenty thou cuts down in the leading direction and twenty thou cuts out in the trailing direction. Size-wise, I tried to attain the same width as the tailstock vee. After checking that it sat flat and square across the ways, I cleaned it up a bit and also made the underside clamp from some black steel. So that was the easy bit done.
Machining the disc needed some thought. There was no accuracy required here but I needed the ability to hold the part and once separated from the hub, this would be nigh on impossible without a faceplate. Holding on the hub, I skimmed the O/D to clean up and took a couple of cuts down the face, then turned it round and took a cleaning cut down the opposite side. I'm running at about 100 RPM and using the power feed to keep a steady cut. I also cleaned up the bore of the hub to facilitate holding later on and, because I didn't fancy trepanning this, started to bore out to the finish I/D using facing cuts rather than sliding cuts. But before I cut right through, I needed to get some milling done while I could still hold it. So it was over to the mill and set up the rotary table, allowing me to mill some guide slots for the bearing supports, or fingers, which I will make later. I started milling with a 12mm cutter but it rang like a bell because of the large overhang so I changed to a 6mm cutter which allowed faster speeds and a better finish.
I also spotted the various drilled holes and the splitting lines before returning the workpiece to the lathe and separating the flange from the hub with more facing cuts. When there was about twenty thou to go, I saw a witness of the cut start to appear on the rear of the workpiece so stopped the lathe and gently broke the flange away from the hub with a hide mallet. The bore was cleaned up with files and the part then split. Offering up to the lathe it appeared that the base of the ring needed to be 7mm above the bed clamp and because I needed to make a piece of angle to fix them together I made this 7mm thick to get the required lift. The lower section sits on the angle and is bolted through with three M5 cap screws. In the photo the top section is shown.
A quick rummage in the "bearings" drawer produced three 626 bearings which are 19mm x 6mm x 6mm and this determined the size of the fingers, which were made from 3/4" x 1/2" black bar, cleaned up all round and milled to be a snug fit in the 16mm slots. A 6mm cross-hole was drilled and reamed and the slot cut away with a 6mm carbide endmill to take the bearings. To create the adjusting slot in the fingers, I stitch-drilled the full length of the slot by centre-drilling at 5mmm intervals and using a 4.7mm drill to clear the material followed by 5.1mm. The only suitable slot drills I have are 3/16" HSS and, because this material was a bit rough and abrasive, it was kinder to the cutter.
The slots were finished at 5.2mm wide by 40mm long which will give a reasonable range at these large diameters. Different fingers can be made as and when required for other diameters. That left the rear hinge and the front clamp to make. The hinge was made from 1" x 1/2" bar with a 1/2" section milled away from each piece and a pivot hole through the middle and the clamp was made from 1" x 1" x 1/8" angle, held together with a nut and bolt when in use. Here is the beast bolted together and on the lathe with the smokebox held rather precariously in the chuck and resting in the steady. Im running at about 100rpm again but not taking any cuts, just making sure it runs OK.
  General Purpose Tapping Fixture  
I've always been comfortable with freehand tapping but after breaking a 12BA on the third hole, and with thirty three still to go, I decided that it was time to make a tapping fixture. Nowadays, my hands aren't steady enough to keep these delicate little taps perfectly upright whilst twisting the wrench. Once again, all these parts were made from surplus materials except the little Jacobs 5/32" chuck which I have a pair of and will take taps with 4mm or 5/32" shanks. I wont describe this in detail because it's very simple; a 3" square baseplate, a 5/8" diameter mild steel column and a head from the same material as the base. The shaft is 1/4" diameter mild steel with a Jacobs No. 0 taper turned on one end. The bearings are roller bearings salvaged from an old printer 7/16" O/D x 1/4" I/D x 7/16" long and the handle is turned from a lump or Delrin, fixed to the shaft with a 3/32" taper pin. The locking screw on the side is M8 nylon and is only to hold the chuck up whilst loading a tap. The head height can be adjusted to suit the workpiece and the alignment is done simply by lowering the chuck jaws down to the hole in the baseplate.
The workpiece doesn't have to sit on the little table, either. Just swing the head round and use the base to rest on any flat surface thus keeping the tap vertical. By holding the fixture in the bench vice it can be used in the horizontal mode, and I found this the most comfortable working position. Tapping the other thirty three holes was achieved inside half an hour and no further breakages occurred. The fixture took a few hours to make but was well worth the time spent. These small taps ain't cheap! And, luckily, I was able to remove the broken tap from the third hole in the workpiece without damage so not quite a disaster.
  Hand-held Dimple-forming Tool  
I've never been particularly happy with any of the methods for producing a dimpled effect on loco and tender steps. I have tried using a punch directly onto the underside of the tread with a backing block of wood, and lightly punching onto brass shimstock to produce an inlay for gluing or soldering into place. I wanted something simple that was repeatable, easy to use, and didn't distort the tread. Most punch actions make the tread curve in the direction of the punching action and any effort to flatten the tread out again flattens the dimple pattern. The other problem is that these all work better if one has three hands, the third hand supporting the work. My solution was to convert a heavy-duty leather hole-punch into an indenting tool. The first job was to remove the brass anvil, which just punched out, and the rotating punch holder which was slightly more problematic. Although I used my advanced butchery skills (junior hacksaw, hammer, cold chisel, verbal encouragement etc) it would have been simpler to just drill straight through the carrier with a 5/8" drill. It was made of one of those horrible aluminium-zinc alloys and not worth trying to adapt. I also discarded the indexing spring as I only require one tool location and would like some fine adjustment of its rotary position.
The tool carrier was remade from mild steel using the same dimensions as the original and a solid mild steel pin made to mount it on. The carrier has a flat milled on it and a 6mm reamed hole to locate the tool bit. The tool bit is from 5/16" diameter mild steel with a 6mm back and the front tapered at ten degrees except for the point which is forty-five degrees. The anvil mounting point was opened up to 6mm and the anvil made from 5/16" mild steel. The M6 thread on the back is to hold it firmly in position but allow easy replacement and the front has a 1/8" diameter nose with a small indent formed with a No.1 centre drill. All the parts were fitted together and checked for alignment, followed by a couple of trial indents. This is a close-up of the tool.
I found that the tool bit had a tendency to rotate away from it's positon so an M5 bolt was used to lock the position after alignment. The hole on view at the back of the tool carrier allows the tool bit to be punched out if it get's stuck. This final picture shows three different sets of dimples. On the left is 18swg material and the dimples are not particularly well-formed, the middle is 20swg brass and they are much crisper. On the right is 8 thou brass shimstock and the inset shows the graph paper that I used as a guide. It just needs a bit of care and attention to get a perfect pattern. Trying to dimple 16swg material failed miserably but may just need more acurate and harder tools. Now that the principle has been proven I am going to try different types of anvil, and may use silver steel which can be hardened for the tool bit. The other tool bits and anvils that I am going to experiment with are for riveting. I think it should be possible to squeeze copper rivets in sizes up to 1/16" and also the smaller brass sizes using this tool. Although there is limited throat depth, such a tool could still come in handy for things like the smokebox rivets (I hope).
  Next item...  
   
  Quill Stop for the Mill  
One of the things that this hobby mill is missing is a deadstop for the quill. Industrial machines usually have these on the front of the quill housing and come in very useful when repeat drilling or milling to a set depth. Our hobby machines appear to rely on using the simple DRO to get to a depth and it's very easy to make a mistake and go too far, ruining the workpiece. I've now made a quill deadstop to help overcome this problem. I dismantled the safety guard and interlocking switch the very first day I got the mill so decided to make use of the guard mounting holes. A pair of blocks were milled up from some 30mm x 12mm flat steel bar and a counterbored hole put in each to take M5 cap screws. A 5mm hole was also drilled to take the vertical rod. With the blocks screwed to the machine, it left a gap of 55mm between them and the maximum travel on the quill is a tad under 50mm. A pair of knurled rings were made from 7/8" dia bar, drilled and tapped M5 and parted off at 4mm thick. A length of M5 allthread was used to make the rod.
To connect to the quill, I would have prefered to make a collar with connecting bar but couldn't find any suitable material. Therefore, I replaced the flimsy, plastic block connecting the DRO tail to the quill with a more substantial block of steel and used a length of flat bar to connect this to the bottom of the stop-rod. I also had to make a new quill-locking screw but, not having any 12mm hex material, made an extension instead. This ensures I don't trap my fingers or skin my knuckles when using (got the tee-shirt). It's a little "spongey" in use but, combined with using the DRO, certainly speeds up jobs like multiple plunge-cuts. This took a couple of hours to make but well worth the time. When a suitable chunk of material appears, I will make a quill collar and dispense with the current connecting bar. Because of the need to dismantle the safety guard, I can't recommend that others copy this exactly but a more able mind than mine may well find an alternative method of mounting the deadstop and keeping the guard.
  Milling Fixture  
I needed to make a large quantity of thin strips and angles from offcuts of sheet steel but edge-milling vertically in a vice was never going to be a sensible option. I decided to invest a couple of hours in making a simple fixture for holding strips of steel and milling the edges true. It is only a simple clamping fixture but allows quick and easily repeatable operations. There was a 240mm length of 40 x 8 black steel in the scrap box and this became the body of the fixture. The edges were milled flat and true to create a clocking face. A series of M5 holes were drilled and tapped at 1" spacings along the length for the clamps and another series half-way between them for the distance fingers. Clamps were made from 1/2" x 3/16" ground flat stock with 5.1mm holes for the clamp screws and M5 tapped holes for the packing screws, grub-screws in this instance. The distance fingers are from 1/2" x 1/8" BMS with a 5.5mm slot milled for most of the length. A pair of 11mm holes were drilled for fixing to the mill table. These four strips of 45 thou steel have been finished at 3/16" wide and are just under 7" long.
By adjusting the grub screws, any thickness of material can be easily clamped without the need for additional packing. The fingers can be adjusted with a vernier caliper before setting the jig on the table. The fixture can also be used for drilling holes in strips of metal, or angles, assuming spacings are correct for the job. Here, an end stop has been clamped into place and the strips rested against it. I was also able to use the jig at the same settings for the roof that the strips will fix to by raising the jig on packing blocks. These are 1.2mm holes for 3/64" brass rivets. The gutter strips on the roof section were drilled with this fixture also. The main advantage of the fixture, however, is the ability to true up thin strips using the side of the end mill rather than the end. The cutting forces are pushing into the fixture rather than at right-angles to it. And the multiple clamps when drilling prevent the thin sheet lifting up at drill breakthrough and raising a large burr on the opposite side. A very simple piece of kit that took a couple of hours to make but well worth the time invested.