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I've got 2 hand file questions

WoodburnBob

Aluminum
Joined
Apr 14, 2004
Location
PDX (Oregon)
Common American pattern hand files aren't flat. There's a relatively concave side and a relatively convex side. If I grind the concave side, will I increase the radius of the convex side? I'm looking to see if I can tighten (reduce) the radius on the convex side.

Second question. What is the best mail order source for uncommon Swiss pattern, e.g., Grobet, files, like the larger Pillar files?
 
This concave/convex thing is news to me. Is this concave across the width, or concave down the length?

How many files did you measure to arrive at this conclusion? Were they older USA-made files or new stuff from asian or south-asian sources? (Rumors abound of substandard files being rolled from scrap plate and then casehardened.)

I can't remember anyone ever mentioning this before, either in person or in print. If this holds true for quality-made files, it's amazing.

For new files, try www.boggstool.com
(No relation. etc.)

John Ruth
P.S. On edit: If there are any flea markets nearby, these should be checked regularly for files and file handles. You'd be amazed at what's in the "boxes of rust" that are usually on the ground under the front edge of the flea market table. Boggs Tool can resharpen files with a wet-blast abrasive process. Rusty files can be de-rusted with phosphoric acid. If the file is shot beyond hope, but has a nice handle, try to talk the price down and buy it for the handle. The shot file becomes material for homemade scraping tools.
 
Curvy flat files have never been a problem for me, so I have not tried to measure or correct any curvature.

Swiss pattern files are made by several companies, and not just in Switzerland. The rule is, if the cut is a number, like 00, 2, 6 etc., then the file is Swiss pattern.

I have lots of Nicholson XF brand Swiss pattern files, and they are still being made. Nicholson files

I have some older Heller Amswiss files, but I think they are no longer made.

I have lots of Vallorbe and Grobet Swiss-made files. Grober USA website

Many US deealers sell Grobet brand tools. Grobet has bought up the old Dixon, HR, Vigor and probably other brand names, so they are almost the only big wholesale outfit left in the jewelry tool business.

Larry
 
I have a number of older Nicholson mill files. They all have a slightly concave and a slightly convex side. Considering how files are made, I would be surprised by perfect flatness. First, you ding the teeth into them, then heat treat them. Then you expect perfect flatness?


Stu
 
Okay, let me try again.

I wouldn't have guessed that this was news to anyone. Evidently, its heresy to some.

I read about this 5 years ago. Since then I check all files to know (and mark) which side is which. It has relevance if one is trying to file flat and accurate...perhaps only to me.

Granted, amount of curve varies from one file to the next. But they vary in dimensions so why would that be a surprise. I measure using a new (5 years) 12" Starrett straightedge. I lay it down the length of the file with light from behind. I've got maybe 40 files from the past 5 years, mostly Nicholson and Simmonds but also a couple high priced German files. This is true, in varying degrees, for all. It's pretty obvious to me.

As Stu says, given the proportions, composition and processes involved, can a file be anything other than imperfectly flat and straight.

I just read the file section in the old Joshua Rose text on machineshop work. They knew this stuff in the 19th century.

So with that stuff out of the way. I still have 2 questions. If you want to believe files are flat. Okay. Make my first question this: I grind down one side. Does that side become concave, convex or remain perfectly flat?
 
I assume you are talking about the curve being in the length? How much variation are you seeing? I have a quantity of new old stock Nicholson's that date from before 1915 and it would be interesting to see if the old ones are worse of better than more modern files.
 
WoodburnBob- agree, and always took it as a matter of course to check which side of the file to use for a given task. I just sight down it. Vaguely remember someone pointing it out to me as a kid, as being a necessary part of file use. About the same time they were telling me not to rub a file back and forth, but to stroke and lift on the return.

I always preferred the bellied side as being easier to work to flat with.

But I don't know the answer to your Q. Surely you have a beat one to try a test on? Or get one at the fleamarket just for the experiment?

smt
 
I'd say that trying to flatten a file would be a lot of work......just grinding one side or anything long and flat and hardened LIKE a file would give you fits. There is so much stress in soemthing like a file it might get worse!!...I would THINK that any side you ground would become the convex side in a hurry....because you were grinding out any stress from that side, BUT still have it inthe other side...thus it might pull to that side....Kinda like taking a cut on a long thin piece of 303 ss.....if you dont hurry up and take a skim cut on the other side...it is gonna warp !!! hec it may warp anyway!!!...I also think it would take a lot of thought to take the curve out in a controlled manner...seems like a ton of work... but I guess if you just did it by hand and kept checking....maybe you could get some results.....

trial and error ...I never thought about the flattnessof a file, because I never try to make stuff flat with a file.....but i can understand that each person has their reasons for doing stuff.....and it is clear to them, if not to everyone else.

do you have a task that needs this flatness, you could tell us about?

thanks and good luck

bob
 
Files are generally made with convex surfaces, that is, they are thicker in the middle than at the ends. This is done to prevent all the teeth from cutting at tha same time, as that would require too much pressure on a file and make it hard to control. A flat surface could not be obtained if the face of the file were straight as there is a tendency to "rock" the file. The convex surface helps to overcome the results of rocking.

This convexity of files also serves another purpose. The pressure applied to a file to make it bite into the work also bends the file more or less, and if the file in it's natural state were perfectly flat, it would be concave during the cutting operation. This would prevent the production of a flat surface, as the file would cut away at the edges of the work and leave a convex surface.

This is a direct quote from the Henry Ford Trade School Shop Theory book.
 
Hello there,

I have made several sets of parallels from old well worn Nicholson lathe files. I just set them down on the magnetic chuck of a surface grinder and took the teeth of each side turning them over every 10 thou. or so and then matching them for width and length. They came out dead straight and have remained so for many years.

Charles
 
I’m no great shakes with a file, so I did some reading in an 1880 book. In the context of filing wide surfaces including surface plates, it says:-

‘It then becomes necessary to localise the action of the file, which of course would be impracticable in filing a flat surface with a flat file. Advantage is therefore taken of the convexity which to a greater or less degree is given to almost all files – partly to enable them to be used in this manner on large surfaces, but more especially on account of the great difficulty which exists in maintaining the exact form of the blank during the processes of cutting and tempering.’
 
R608: Yes, lengthwise. Old vs. new has no meaning to me, since I don't see convexity as a negative. It would be a purpose made positive. Not a flaw but a feature. I can imagine the old guys made a point of going to the trouble to put in the convexity for some files. For instance, look up sales literature on Swiss pattern "hand" and "pillar" files. They are made "tapered lengthwise in thickness". I'm not exactly sure if it's just middle to the tip, or middle to the tip and the tang. I'm looking for the latter.

Stephen: I've been a fan of yours since the old Badger Pond (where I went by 'treeshin') days and your 3 issue article on the St. James Bay casting. Needless to say, your confirmation I'm not psychotic is much appreciated.

OCM: Dad was born in Woodburn 1906, me in 1947. I'm in PDX now but I left my heart and a lot of semen in Woodburn. Both are increasingly and fondly on my mind as I grow older. I just ordered 2 Grobet Valtitan "hand" files from Frei. I'm anxious to see if their convexity goes both ways out from the middle.

dvice: I'm in no way interested in trying to flatten or straighten files. I'm interested in increasing the amount of convexity on the already convex side. And, no, I don't want to bend the file over a penny, fulcrum or such, using wire, clamps or contraptions. Yes, I'm picky.

Mentioning the task will probably only divert responses away from my core question, but it's no secret. I'm a little obsessed with getting handplane soles flat, not gauge block flat, but blued surface plate flat. I don't need 20 bearing point per inch flatness. I don't need oil pockets. I've scraped my share of soles. I want to explore file work and have had some early success.

Please don't inform me about milling and surface grinding. Sure, I'd love to fool with a 20" shaper. Where do I put one? The downstairs bath? I've milled enough plane soles to know I'm not impressed...it's a workholding and deformation issue with thin and unpredictable complex cast iron casting, I think.

I'm not going to buy a surface grinder for this. It's a hobby, an avocation. If old time apprentices were given as a first task filing and lapping small perfect cubes, I don't see why I can't entertain myself and learn to get a handplane sole flat with hand files.

Precision Tools and Asquith: Thanks for the addition confirmation and support that files are and should be a little convex rather than "perfectly" flat, if you try to flatten a surface.

Still no materials/physics/metalurgically based answer to the orginal question! Fascinating!

When I milled the soles of some Stanley Bailey planes to "get them flat". They became concave!

Theory, I thought, would predict they'd become convex. Milling should remove forces in tension, right? They should become convex overnight. They didn't. They became concave overnight. This implies I milled away one side of a pair of steady state compressive forces. This strikes me as very paradoxical. Maybe I've got it totally wrong.

Anyway, this is what prompts my core question. Take a hardened steel file, grind off the teeth on one side. What shape, based on metal working principles, should the file take on? An incredibly fundamental question, wouldn't you say?
 
Files are not particularly likely to have strains in them, but if they did, it would be difficult to predict how they would behave when released by grinding or other operation.

I would not be surprised that the common file found in the box stores today does not have the convexity that was built into them years ago when they were a tool used for precise work. Today's file is as likely to be used as a paint stirrer as it is for controlled metal removal.
 
ulav8r: I'm just asking for an educated answer to my basic question. Surely, those who've ground hardened flat steel must have basic knowledge about what will happen and why?

If the answer is, "Everyone knows you can't predict what will happen", I'd welcome that, as long as it's based in reason or experience and not ignorance and indifference. If I read PrecisionTools correctly, his answer is: unpredictable.

If that's what everyone says, I think it would then be interesting to grind one side of 100 files. Should we expect 1/3 convex, 1/3 concave, 1/3 straight and flat? It's unpredictable whether I'll die today or not, but the probablities aren't equal (I hope).

I'll now shut up for a day and listen.
 
"ulav8r: I'm just asking for an educated answer to my basic question. Surely, those who've ground hardened flat steel must have basic knowledge about what will happen and why?
"

yeah and like I mentioned before..i think it will warp AWAY from the ground side....

maybe it will be stiff enoug to resist that bending force. who knows....most guys will try to travel down a path with more predictable results.....

grind the side concave side and maybe it will straighten up some..

good luck.....

If it were me, id just go to a place that has 25 files and pick the flattest one......and id pick up every files i ever saw for sale, and check it out...always looking for the flat one....I seriously doubt that files today are made with this curve engineered into them.....its a side effect id say

bob
 
I "think" if you grind the concave side on a surface grinder (which it is understood that you do not have nor particularly want for your space & circumstances, but it is the way I can think about it) that the bow will either increase or stay about the same. I don't "think" it will bow the other way.

To increase the odds of a deeper bow in the existing direction: Put the file on a couple/three thicknesses of typing paper to protect the chuck. Concave side up. Use full magnetic power to warp the file down as flat as possible.

Use the Z axis table traverse, no coolant and a dull wheel. run the table in & out at the center and then work back & forth to each end of the file, dropping the wheel and useing the full width, toward each end of the file, letting the work get just as hot as you like. The ends will most likely pop up off the chuck and you can continue until the bow suits, or the file flys off the chuck :D .

I'm enjoying the incongruous concept of trying to grind (sort of) flat work so it bows, so no doubt this is coming across a bit flip. But it is not intended to be rude. It is IME as good a recipe as any for your objective.

An analagous situation would be to use an old large diameter sandstone wheel, hold the ends of the file with something so you can stand the heat, and grind the full width of the back with no coolant, press hard.

OTOH, for either method, there is going to be a fine line between optimum heat for the best shrinkage, and softening the teeth on the file.

I'll be curious to hear of any experiments.

I would take (have done) the approach someone else mentioned, go to fleamarkets, stores, cabin fever, wherever NOS files are sold and pick the ones most warped if that is the preferred condition for a certain task.

Thanks for the compliment!
smt
 
The stresses left in any heat treated metal object cannot be quantified or controled with any degree of predictability. That is why stress relieving techniques are employed and why hardness is allways sacrificed to stabillity. The harder something is left the more likely it is to distort later. Time will equalise stress but he resultant shape of the part cannot be predicted with any certainty. This is why good tool makers allways used to leave their rough castings in a field behind the foundry to "season" for in some cases years, before starting to work them into precision shape. Hardness was the most important quallity in a file and in veiw of the usual shape ie. long and thin, the quest for the ultimate cutting condition would naturaly leave the tool bent.
A good file salesman would naturally make this an advantage!
If all you want to do is to increase the bend why not soften it, bend it, and reharden it?
A charcoal hibatchi blown up with a hair dryer will provide you with all the heat you need. Test for the transition point with a magnet on a wire, it will no longer be atracted to the steel when the correct hardening temprature has been reached and if you quench it in saturated brine it will pobably end up harder than it left the factory.
All the fun you will have doing this will distract you from regretting all that semen you left in Woburn.
Charles.
 
Quote Woodburn Bob <since I don't see convexity as a negative. It would be a purpose made positive. Not a flaw but a feature. I can imagine the old guys made a point of going to the trouble to put in the convexity for some files>

I'm inclined to think this bent file 'feature' is nothing more than a result of the manufacturing process which is been exploited by creative marketing and employed by skillful users. Having eyeballed 17 of my Nicholson files, I've concluded the bend radius is not consistant in either radius or location along the length.

However, back to you querry, how to make it flat. Any time you donk with stress, unintended consequences will surely appear. First thought in my mind is peening the back (concave/sacrificial face) whilst making flatness observations. With due dilligence and patience you may able to control flatness end to end & side to side, and of course, twist. During the process, individual teeth will likely require special attention. I think beginning with safe edge files and stoned edge radii would get you started.

I eagerly await your conclusions prior to putting a file to my Baileys.

Lloyd
 








 
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