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Filing Technique

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KWIL29/11/2021 11:01:19
3563 forum posts
70 photos
Posted by Mark Rand on 29/11/2021 09:13:34:

Trouble is that no one seems to make coarse files any more. Even bastard files are less common than they could be.

ARC Eurotrade have Bastard files as well as smooth. Made I believe in Portugal by traditional methods, I have found them very satisfactory.

Rod Renshaw29/11/2021 12:59:45
376 forum posts
2 photos

Interesting thread, everyone seems to have had different experiences.

Re Tim's thoughts on shapes of files, I think it was Tubal Cain who wrote that you can't file a flat surface with a flat file, the file has to be just a little convex.

I also liked the post on things learned at school. There was a comedian on the radio a few weeks ago, brought up in the East End, worked as a market porter, who explained that his school was a real cockney school who educated pupils for their future roles in life. He said they had big woodworking and metal working depts. In his second year he made an ashtray and in the third a corkscrew, and in the fourth year he made a pram. Well, it made me laugh.


Nigel Graham 229/11/2021 23:00:51
2284 forum posts
33 photos

I suppose like most of us I was taught to lift the file, or hacksaw, for the return stroke, or at any rate relieve the pressure on it.

Reading this thread it occurred to me that lifting the tool clear might do more harm than good, potentially chipping teeth, by the slight but many-times repeated hammer blow when you start the next cutting stroke.

I don't know if that's a likely hazard or not, but I don't recall ever reading or hearing it anywhere. Even if not it may make consistency of action harder.

Provided you let the file slide back across the metal, I don't see leaving it in contact as potentially any more damaging than for example the action of a shaping-machine on hauling the tool back for the next cut. On a slotting-machine, as far as I can see, there is no relief for the tool on the return.

Edgar Westbury, in his Lathe Accessories - How to make and use them, p.76, shows a simple keyway slotting-tool in which the cutter itself swings on a pin, rather as on a shaper. Personally I'd be more worried about using my lathe in the way he suggests (winding the saddle back and forth), than preserving the edge of a very simple cutter! I think the modern equivalent, like a miniature shaper that fits on the saddle or tool-post, also typically uses a rigid tool.

My copy of that book, by the way, is the latest... 1955, cover price 3/6.


So perhaps we do worry a bit more than we need about filing; but better that than wear them prematurely.

Mark Rand29/11/2021 23:55:18
1313 forum posts
38 photos

One thing that was hammered into us at the GEC Machines, Rugby Apprentice training school, by Mr Arthur Dobson, was that HSS had a cutting speed of about 100 feet per minute on steel and carbon tool steel had a cutting speed of half that.

The relevance of this was that if you were making more than one stroke per second with a file or a hacksaw, you were almost certainly overheating the cutting edges and could expect a clout around the ear.

I bear this in mind when using files and saws and have also been known to remonstrate with workers who are in too much of a hurry.

DiogenesII30/11/2021 07:35:11
589 forum posts
234 photos

It's funny how things stay in the memory - one of the best pieces of hacksawing advice "keep your bl**dy feet still" was drummed into me at the age of 11 or 12 by Jack Hovell, I still hear him perfectly to this day..

+1 for the 'Tome..' files from ARC..

Tim Stevens30/11/2021 10:00:28
1622 forum posts

I wonder if Mr Dobson (see Mark rand's post above) ever thought hard about his advice. To affect the temper of steel you need to get it hot enough to change its temper colour or 'blueing' - starting (as every metalsmith knows) with the palest yellow and ending with purple. His advice - if based on good science - would mean that filing quickly produces blued swarf. Not in my (60 years) of experience it doesn't.

Regards, Tim

Mark Rand30/11/2021 10:45:57
1313 forum posts
38 photos

Actually, O1 steel, which files were made from, loses hardnes fairly linearly from 100°C to 700°C. 100-200° temperatures are easily produced at the teeth with hand filing and sawing.

Edited By Mark Rand on 30/11/2021 10:46:42

Neil Wyatt30/11/2021 12:26:35
19076 forum posts
736 photos
80 articles
Posted by Mark Rand on 30/11/2021 10:45:57:

Actually, O1 steel, which files were made from, loses hardnes fairly linearly from 100°C to 700°C. 100-200° temperatures are easily produced at the teeth with hand filing and sawing.

Edited By Mark Rand on 30/11/2021 10:46:42

But files aren't normally glass hard or they would shatter easily in normal use, the tempering they receive is probably in that range, and the tang can be very soft some times too soft!

Tony Pratt 130/11/2021 14:29:44
2024 forum posts
12 photos
Posted by Mark Rand on 30/11/2021 10:45:57:

Actually, O1 steel, which files were made from, loses hardness fairly linearly from 100°C to 700°C. 100-200° temperatures are easily produced at the teeth with hand filing and sawing.

Edited By Mark Rand on 30/11/2021 10:46:42

Even IF hand files got to 200°C in use the hardness will hardly be affected maybe 62 RC? I have seen needle files snap a few times so they are very hard / brittle anyway, they will be tempered but I believe not too much.


Harry Wilkes30/11/2021 16:16:56
1371 forum posts
66 photos

My problem is can't file for toffee sad even before the Arthritis and Carpal Tunnel I was not that great I can however cut straight with hacksaw wink


Bo'sun30/11/2021 16:47:03
619 forum posts
2 photos
Posted by Andy Stopford on 27/11/2021 20:04:26:

Of course, once you know, it seems reasonable that dragging the file back increases wear on it's teeth - but is it true?

This guy decided to find out:

Aside from attempting to answer the question, its a nice demonstration that you can use a shaper to do all sorts of things it's manufacturers never intended (when I had one, it occasionally did duty as a tool and cutter grinder for horizontal milling cutters).

An interesting video Andy, although it did go on a bit and was perhaps a little over the top. But some surprising results none the less.

old mart30/11/2021 16:49:31
3901 forum posts
268 photos

I keep a few good quality files at the museum, including a number of NOS Stubbs, they no not get lent out to be abused.

Andy Stopford30/11/2021 19:22:17
165 forum posts
25 photos

Well, today I was doing some filing, and guess what, I do lift the file on the return stroke! Admittedly I was shaping a bit of aluminium to fit into the moulded plastic case of a Dremel-type tool I was repairing so I needed to keep eyeballing the developing shape, but even so...

So do I always do it? I don't know, I'll have to catch myself next time I'm filing without thinking about it first.

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