Filing Technique

Not having had any training in metal strangling, for manual workshop skills (filing, sawing, etc) I've mostly made it up as I went along, with varying degrees of success.

So, when filing, I usually let the file drag on the return stroke unless working with sticky aluminium or similar, when lifting the file reduces clogging. I certainly had no idea this was regarded as a heinous crime by those who have had an education in these things.

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:

https://www.youtube.com/watch?v=52d0TmmQ5yI

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).

That's interesting. Another example of experiment winning out over intuition.

dave8

What do filing machines do ? What do ratchet wheels do ? What do hacksaws do ?

I was never taught to back off the file on the back stroke, however the effort exerted on the 'push' is far greater than the 'pull' . A more heinous crime is to sling all your files into a drawer (like I do) so that they can rub together.

Bob

I did read (in a US Army training manual, I think) that it's OK, indeed recommended, to drag it on the return if the metal is soft, as it helps to unclog the teeth. On hard materials, do not drag it.

Having said that, I agree with Speedy that the force applied on the push stroke is so much greater than the pull, I don't see any harm in keeping the file in contact all the time.

Just an aside on ratchets, I was taught to always depress the button when applying a car handbrake, so as not to wear out the teeth and pawl.

Rob

No problem at all with gently dragging the file on the back stroke, as you would when using a wood saw. I'm still using files issued to me as an apprentice, they're not as sharp as they were when new, but are useable. I never lift off when draw filing either.

Got me thinking about using a Japanese pull saw, they never get lifted off on the non cutting stroke either.

IanJ

I was just wondering if theres not two arguments regarding filing mixed up, the one is damaging a file & clogging of a file using the right file versus achiving a certain shape more accurate by using just forward pressure, eliminating uncoordinated backwards filing removing accidently metal you did not want to, and then have to do repeat unnecessary actions-?
I have to remake small part for an old airgun, and am curious as theres not much to file away wrong-? I am still thinking about how to go about it.

If you watch the video you will notice that the pressure applied to the backstrokes is not reduced.

In my view there is only one way to file effectively and productively......

I have noticed that many of the people who have alot to say about filing methods being unimportant, don't actually need to file much and have never done so. However, once there is a real need to remove lots of metal accuately then there is usually a quick change to 'the right way'

In my clock club (EFHC) there are people who will do almost anything and use extreme mental excercise to NOT have to file....the easiest filing job involves sometimes two different milling machines and even CNC and filing is now trully a 'lost art' for the vast population of western countries along with many other forms of hand/eye/tool dexterity.

It has been my lot to hve to impart the secrets of accurate filing to at least seven other people and I have been amused by the way they glaze over when you get to the fine details....NONE of those people took up my guidance initially and EVERY SINGLE ONE eventually came to the right way of filing once the real need became vital.

Once you get into making clocks from scratch by hand files suddenly become a vital set of tools as they were in antiquity and people start asking to look at the said clocks using magnifying glasses......But most people who make things don't need to file nowadays and most don't even own a file worthy of the name. Like most things in life it's "horses for courses".

Bob's observation explains what's going on. Before milling machines, and vertical mills in particular, vast amounts of metal were removed by filing. Considerable effort went into doing it fast and accurately, which meant choosing the right type of file for the material in terms of coarseness, sharpness and tooth configuration. Old-time filers used a vast range of different files, and, because they were expensive, did everything they could to squeeze more life out of them.

Modern amateur filers aren't in the same game. We do relatively little filing (none at all if I can manage it), and files are so cheap there's no need to mollycoddle them. Our views would change if we had to buy tools at Victorian prices and feed a family by filing year after year on piece rates.

My files get used, but it's all light semi-skilled stuff. The new files I bought nearly ten years ago are still in good condition. Nonetheless I keep a set for brass and another for steel. Although the ones used on steel seem as efficient as ever, using them on Brass shows they aren't in tip-top condition. Not being 'as-new' sharp doesn't matter on steel, but it does on Brass.

I suspect leaving a file in contact on the backstroke doesn't do obvious damage unless the file is used persistently, and the effect is to reduce its effective life, not instant issues.

More to filing than most of us appreciate. Unwise I think to jump to conclusions based on pottering in a shed or watching internet videos. Really difficult to design experiments and analyse the results; dead easy to get the wrong end of the stick.

Dave

Except on early Triumph Spitfire sports cars (and probably others) with a 'fly off' handbrake which worked the other way round.

You had to press the button as you lifted the lever to make the pawl drag and catch to put the handbrake on and lifted the lever slightly without touching the button to release the brake.

Edited By Nick Clarke 3 on 28/11/2021 10:30:53

Modern files may be cheaper than in the old days, but they are not remotely as 'good'. Not the steel, exactly, but the care and expertise with which they are made. Flat files are not flat, for instance, the edges are not square to the faces, etc. Files for serious professionals seem to be OK still - chain-saw files are still excellent for slotting the holes that you went to enormous trouble to position accurately. Some of the worst examples are sold as needle files, - they really are hopeless.

Cheers, Tim

It occurs to me, and please bear in mind that I am most definitely NOT an expert in filing, that failing to lift the file off on the return stroke runs the risk of knocking off the tops of the teeth, especially if someone attempts to make the file cut on the reverse stroke. I must admit though that I do indeed leave the file in contact with the teeth on the reverse stroke as what I have found is that lifting off causes me to lose the attitude (is that the correct term?) that the file takes with respect to the surface. However, I definitely do NOT attempt to make the file cut on the reverse.

In respect of draw filing, since this is, as I understand it, a recognised technique, then what about using double cut files? It seems to me that these files will then allow cuts to be made in both directions. But what about single cut files. Do they cut in what might be called the reverse action? And in any case, which way are the single cut file teeth slanted. Does this affect the draw filing cut? I don't know. All I know is that I am not a good filer and have difficulty in obtaining a flat surface.

One thing I have noticed recently is that some of the recent files I have bought appear to have a slight bend in them near to the tip (???) of the file, so much so that I have taken to using this to create slight hollows where required or to eliminate high spots. Are these faulty files? Or are they deliberately made this way?

Peter G. Shaw

Hi Peter

Double-cut files tend to have the teeth all pointing away from the handle end, arranged in two rows 'tilted' to left, and right. So, both sets of teeth cut on the forward stroke. Draw filing gives better results (in my experience) using single-cut or 'mill' files, as there is less tendency to 'pin' (where a lump of the filed metal sticks to the file) - but good results can be obtained with double-cut files too.

If you use draw filing a lot, you might look at the 'lathe files' sold by ARC. They have the single sets of cutting edges at a steeper angle to the blade, and they might be more effective for draw-filing too.

Yes, files do tend to be less than perfectly straight. I think this is an effect of the hardening process. It can be very useful to use such curves to smooth a surface hollow, for example. It is also possible to create a bend (temporary) by holding the file in a distorted grip, for the same outcome. There are files deliberately made with bends - they tend to be shorter, and often double-ended, and are called rifflers.

I expect all these names are UK only - our cousins over the pond were very careless in inventing their own words for things with perfectly good English names.

Keep at it - Tim

Digressing a bit, some years ago there was an article in either ME or MEW on reconditioning your files. I have been doing this for years and for me it works OK. Briefly the article said, wire brush the file, poke out any stiff / awkward particles with a sharp scriber and submerge the file in car battery acid, and for that I use a tall plastic sweet jar. ( can get battery acid now days ?) Following the instructions, I leave the files over night in the acid and have a look at the progress in the morning, might give them a day longer if necessary. Next, with my long plastic gloves on I take the files out of the acid and give them a wash. Then I dry the files, using a hot air paint stripper, then give them an oiling, otherwise if you just leave the file after drying they rust very quickly. John

second ratchet aside;.......I enjoy filing and find it quite theraputic, not to say cathartic. However, over the lock-down I filed up the ratchet for my latest clock by hand...16 teeth and not too much accuracy required. One eye was on the nearby TV and then 'Montalbano' came on....I continued filing and reading the sub-titles while following the plot. Towards the end of the episode I was also nearing the completion of all the teeth, but then found that I had 12 teeth pointing in one direction and the remainder pointing in the other direction.........

.........Always pays to have the brain properly engaged!

Thanks Tim,

At least I don't have a set of faulty files!

Yes, I suppose I should keep trying.

Peter G. Shaw

Dave -

At one time filing was indeed almost the only way to remove metal but much of any significant roughing was also by hammer and cold-chisel. That itself probably needed a good deal of skill to be at all efficient.

I have encountered no treatise to speak of, on the technique but I think it involved cutting lots of narrow grooves across the surface.

No wonder milling-machines began to appear in the very early 19C.

'

According to tomorrowsworldtoday.com; the first is attributed to the American inventor of the cotton-gin, Eli Witney, developing it in 1818 for gun-manufacturing. However its ancestry of course was already well-established among clock-makers, by the wheel-cutting engine; and the clock-makers also had rotary filing tools mounted on the lathe spindle.

(That title may make you think as I did that it's a BBC furtherance of the Tomorrows' World TV show, but whilst the BBC has retained the title, this one is clearly American and as I found subsequently, grossly over-simplified.)

Wikipedia is much more exhaustive in its history, reducing Witney's role, crediting the first true milling-machine probably to a Samuel Rehe in 1783 but stating the real early history is vague as many engineers were working on similar developments. It does honourably mention, with a picture, James Nasmyth's machine for cutting hexagons on work-pieces held in an indexer.

Salient to this thread though, for a long time the milling-machine was considered a roughing-out tool, with hand-filing to finish the parts.

Needle files hopeless? Probably are if dirt cheap from an exhibition stand. Case of getting what you pay for. Real Swiss files made by Swiss manufacturers are very much more expensive and quality to match.

I am old enough and lucky enough, to have had the benefit of metal work (and wood butchery) at school. (Also, practical house wiring with Megger testing, plumbing instruction as well.) Quite a useful school. I was taught to use all 3 grades of file, if necessary when a lot of metal removal was needed. Coarse, 2 nd cut and smooth. They were kept separately in wooden racks and the visible part of the tang was painted for easy recognition. Red = Coarse, Green( I think) = 2 nd, white = Smooth. This idea has been continued by me on all sorts of things like red paint backdoor key, red and green for workshop keys. White paint on BA taps and dies and number series drills. Dark red for metrics. Light red for BSW. Hacksaw blades also painted at one end, at rear of teeth so indicating direction to fit in the frame, colour according to tpi. Another idea is to use a small piece of brass sheet to scrap across the file teeth to dislodge all the bits of metal swarf clogging the teeth. Fast metal removal is achieved by filing one way creating small furrows in the work, followed by cross- filing at an angle, cutting across the previously formed ridges. Same trick works on wood with a Surform tool.

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

Personally I think the most important thing is can you begin the stroke at the same angle consistantly. I find that lifting the file on the back stroke slows me down and I get more consistant results. Each stroke being more deliberate. I do however spend most of my filing time creating particular shapes or flats rather than shifting a lot of metal.

regards Martin