Steve's Britannia

Tools, Jigs and other bits (page 2)

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.

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).

Rotating Loco Stand

Inspired by the loco stand described by Bob Shephard, I have made a similar contraption to support my Britannia. Many of the components are a direct copy of Bob's constuction so many thanks to him for sharing photos of it. I started by purchasing a Clarke's 450Kg engine stand from Machine Mart and building it up as designed. Three things became immediately apparent; the front support was too long, the height was too low and the fixed wheels on the rear needed to replaced with castors. I reduced the length of the front support by 300mm to bring the front-to-back dimension to approximately 600mm and redrilled the 12mm hole for bolting to the upright.

Next, I sawed off the lugs that carry the rear wheels and drilled new holes to take a pair of castors. These came from Toolstation, part no 70389. I chose these because they can be mounted with a single M10 bolt through the swivel base, swapping front to back to get the stand more level. Finally, I cut the vertical tube and extended it by bolting a pair of home-made "U" channels around the two halves with 150mm gap between. The "U" channel was prepared on the mill by cutting the side off of some 50mm square box section using a slitting saw. A pair of flat panels were cut from sheet steel to fill the gap between the sides of the risers and M10 bolts were used throughout.

The rotating frame is made from 50x40x6 steel angle, chosen because that is what the local forge had on the shelf, and was bolted together followed by fully welding the corner joints. I also made a pair of end plates which can be bolted on and will have wooden buffer blocks fixed to them. The right-hand end is arranged so that the loco can be wheeled on from this end. A new longer locking pin was made because the original was far too sloppy, and the lower section of the cross-tube drilled to take the pin right through.

The "rails" are covered with self-adhesive draught excluder to protect the loco wheels. A pair of clamps have been made that fix on top of the loco frames and to the underside of the rotating frame. This allows the loco to be fully inverted with no risk of something breaking and I use the axle-box spacers that I made to keep the suspension at the normal ride-height to save damaging the springs by having them fully compressed all the time. The frame can be rotated to eight positions and can be stored in the vertical position when not required to save space.

16/11/2018 - It flexes too much and am working on some modifications including a rolling road on the other side.

Rolling Road

Standing for ages holding an air gun to the end of a piece of hose was less than appealing so I decided to make up an air supply system for fixing to the loco to assist with running in. I also modified the loco stand to both strengthen it and create a rolling road. Starting with some 25mm x 3mm steel angle I cut six pieces at about 4" long, drilling clearance holes for M8 in one side and a 9mm slot in the other side. Pins were made from 12mm dia mild steel, threaded M8 on the back and turned to 7mm on the front for a press fit into the bearings. These are 627ZZ.

The loco stand was dismantled and six pairs of holes drilled 8.2mm dia. The choice of angle iron for the frames enabled simple modification by bolting the rolling sections on one side leaving the other side clear to accomodate the loco when it's bogie and pony truck are fitted. Compared to the photo in the "Loco Stand" post, the modifications to the front are clearly visible giving a much more stable arrangement.

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.

Next item...