Innholdsfortegnelse for April 2023 i Model Engineer & Workshop

A bit of Repurposing I paid a visit to 'The Works' recently. For readers not familiar with this establishment, it's a chain that started off specialising in remaindered books but has branched out into various areas including basic craft supplies. I was mainly looking to pick up some cheap paintbrushes, but I saw a few things that might be useful in your workshop. The basic paintbrush stand in the photo is a great little organiser, but my first thought was that it would also make a handy stand for my collection of small files. It comes flat packed and the construction would allow of the three uprights being shortened by an inch or two to better suit files. My 3D printed version is shown next to it, but I've come…

Using the Silicone Mould A plaster casting was taken from the mould by filling it with plaster of Paris. photo 68 shows the set up using a spirit level and lolly sticks to level the mould as my bench has warped. The filled mould is shown in photo 69 and a painted casting in photo 70. A similar process was used to produce a thistle plaque shown cast in plaster in photo 71. A high temperature silicone rubber was used to make a mould so that a cast could be made in pewter. In photo 72 the mould is being dusted with talc to permit easier removal of the finished casting. Due to the cost and weight involved the base of the plaque was not cast and metal only added…

TIP OF THE MONTH WINNER! A Neater Tailstock Index This month’s winner is Mike Hurley whose neat improvements to an old idea make it worth sharing. Although my lathe tailstock has a zeroing dial calibrated in .05mm increments, I sometimes feel it a bid fiddly when just needing to roughly drill a hole to 'several mm' deep, and I can never find my 6" rule when needed! So I resurrected an old unused manual vernier caliper, fitted it to a block of alloy bored to fit the barrel, clamping with a socket screw. Superglued a simple brass indicator to the tailstock top and it works a treat, easily adjusted. Nothing particularly original or novel but does the job for me. We have £30 in gift vouchers courtesy of engineering suppliers…

It's possible to sharpen the conical part of centring drills, but this is of little interest due to the small wear and low cost of these tools nowadays. A suitable accessory for this task for the "Quorn” T&C grinder was described by Professor Chaddock. Sharpening the conical part of counter sink drills. This works very well provided the cutting edges don't go to the centre, the relief angle is small in this case (only 1° at the outside of the tool), photo1. The routine is the same as for sharpening taps. Sharpening (or making) single lip engraving cutters See photo 2. A special cam, fig. 1, is used as "rotation stop” for a simple rotation of the cutter against the grinding wheel plane. The dividing collar is in contact with…

Tailstock For most work the tailstock needs to be aligned so its centre is aligned horizontally and vertically with that of the headstock. If the tailstock is offset, drills and reamers, and any other tool carried in the tailstock will not cut accurately. Small tools, especially centre drills, may be broken, and in particular reamers will cut oversize. Being held off centre it will cut more on one side than the other, and act like a boring bar to give an oversize hole. Ideally, before checking the alignment of the tailstock, it should be ensured that the bed of the lathe is free of twist. If the lathe bed is twisted, it is likely that long cuts will be tapered. The means of checking for, and correcting, any twist is…

If you need to bore a hole in the lathe to a precise depth (say 0.500") in relation to the machined end of the workpiece in the chuck, take an arbitrary feeler gauge of (say) 0.006” thickness, set the leadscrew hand-wheel to precisely 119 (assuming a leadscrew pitch of 0.125”), advance the boring tool using the top slide to just touch the feeler gauge held between tool tip and workpiece, photo 1, then lock the top slide. You then know that four revolutions of the hand-wheel will give the bore a depth of precisely 0.500”. I would normally bore the hole to within a few thou of the desired diameter by boring to a depth of 0.495”, leaving 0.005” for a finishing cut. It's very similar if you use a…

BEGINNERS WORKSHOP These articles by Geometer (Ian Bradley) were written about half a century ago. While they contain much good advice, they also contain references to things that may be out of date or describe practices or materials that we would not use today either because much better ways are available of for safety reasons. These articles are offered for their historic interest and because they may inspire more modern approaches as well as reminding us how our hobby was practiced in the past. DEPENDING ON EQUIPMENT available and, to some extent, on the condition of the valves themselves, there are various ways by which they can be tested and faced durin decarbonising or overhaul of an engine-aspects of reconditioning not dealt with in previous articles. The problem, of course,…