Filing rest - hardened guides ruining files

"what colour do you temper them to as I don't see this being mentioned just "hardened"

Not sure why you would need to temper something that won't see a shock load?

As tempering also reduces the hardness as well as the brittleness of the metal I was just curious if any of the advocates of hardening then tempered and possibly did it so that the rollers were just a fraction softer than the average file. This would mean they wear well but don't damage files, also could be less likely to skid as the OP is getting.

Tempered to achieve a hardness slightly less than that of a file? Seems possible but would require better temperature control than I can manage with a gas ring.

Many thanks to everyone who responded to my post. I am indeed a filing rest for use with a headstock indexer on the lathe and not filing buttons for rounding parts held in a vice. The files I've been using are Swiss Vallorbe/Grobe files, hence why I can't afford to ruin any more! I'll try making the guides from silver steel, unhardened. The guides are designed to rotate, and they do rotate easily by hand. However, the files skid over them, and I assume this is contributing to the wear.

I assume this (unhardened silver steel) should cure the problem, though if not I'll try another material such as PTFE or Delrin.

Many thanks,

Mike

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I had refrained from contributing to this discussion, Mike … but that observation worries me
I would infer that you are applying too much pressure

What sort of scale are you working at ?

I recall a particularly impressive demonstration by an expert watchmaker … filing a square on a winding shaft he was making from 2mm diameter stock.

His filing technique was more akin to ‘stroking’

If you are removing a lot of metal, it may be worth roughing it out freehand, and only using the filing-rest for the finishing.

MichaelG.

If the Domestic Authority allows it, temper in the oven! Light Straw, which is probably still too hard, is about 200°C, so soaking in an oven at 180°C for half an hour or more should do the trick.

My book emphasises the need for speed. The workpiece must go straight into the oven after being hardened, preferably while the metal is still above about 80°C. Taking a few minutes to sort one's act out before getting the metal into the oven makes it likely it will already be stuck in a hard condition rather than continuing to soften down as required. Tempering done accurately to get to a specific combination of hardness and toughness is quite a slow process - hours or longer. For my needs, I either leave silver steel hard and hope it doesn't shatter, or temper it unscientifically, basically hoping holding it rough and ready at a lower temperature for a bit will be good enough.

If the need for speed is as important as my book suggests, it collides with the ordinary way of judging temperature by looking for straw to blue oxide colour changes as the job is gently heated in a flame. To see them the job has to be cleaned first, which wastes valuable seconds. My book avoids the issue by assuming a thermostatically controlled oven is available, and no cleaning is necessary.

Only used filing buttons a few times and left them soft, ordinary mild-steel. They weren't expected to last and I was too lazy to find silver-steel and harden it! Worked OK for what I wanted, but not much of a test.

Dave

Indeed. Or look at holding a milling cutter in the lathe chuck and hold the job in the toolpost, or clamped to the vertical slide. You can then use one of those small digital inclinometer/angle gauges to set the angle of the first flat to make the second and so on.

If the filing rest is set up properly, the file should only just touch the rollers as the job is brought to size. The file should not be rubbing hard against the rollers

Roy

The actual job is a three part viola bow adjuster, made from ebony with silver rings. I turn this to size (to the measurement across the octagon corners), then file to an octagon, 9.5mm in width. This involves removing, at most, 15thous of silver and ebony from each face. The adjuster is held by its 3mm steel shaft, threaded and glued into the ebony. Of course, this doesn’t offer the most rigid setup for the workpiece!

It may well be that I’ve been pressing on the files too hard, though I can’t risk any more of my expensive Swiss files, hence my intention of trying non-hardened guide rollers.

My other options are:

- filing the octagon by hand, workpiece held in a small engineering vice

- milling the octagon (very gently!) on my milling machine using an indexing head

I realise this is a VERY unusual workpiece, bordering on jewellery making, but I’m sure that engineering principles still apply.

Mike

Dave,

What is the book, please?

I have Tubal Cain's book about heat treatment which I use as a bible. Without looking at it I remember tempering from, let's say 200C, gives a different result than that from room temperature.

Apologies to all those who think replies should only be relevant to the original question. Perhaps a thread should be started on the hijacking of topics (although I don't think this one has been).

JA

if you are worried that your workpiece is flimsy why not support it from underneath???

I would simply attach a thin bit of shim, say 1/2mm to the rear half of the file and let that run against the rollers.

I made a filing rest for octagonal silver and ebony violin/cello adjusters. I used mini bearings from Arceurotrade and haven’t had problems.
Leo

Leo: That’s very interesting. Are you able to send me a photo of the filing rest you described?

Mike

Are you using one of those sets of tiny Vallorbe Swiss files that are about 150mm long including the handle/tang? Akin to needle files or riffler files? If so that may be your problem.

Try using something like a 10" flat file, as shown in ET Westbury's book with the original design rest that Hemingway now sell. Although you are doing small delicate work, 10" long flat fine single-cut file such as a millsaw file, or maybe even a second-cut file, should work ok and will spread the load on the rollers over a greater area. And will need a lot less back-and-forth movement. You could then try using cheap hardware store files and regard them as disposable if wear continues.