Thread: Saw sharpening files 101

Originally Posted by FenceFurniture

Ian, I think we have to be quite specific about our statements these days, after what we have learnt on this journey.

We can say that your statement is correct for Vallorbe Needle files, because we have the data in front of us. We cannot say that for Needles in general, but it is also true of Bahco Needles:

Yep, point well-made & well-taken! You would think, given my background, I would be much more cautious about making any definite statements, but I slipped up this time....

Originally Posted by FenceFurniture

Are yez confused again yet? Let me know if you're not, and I'll do my best.

Well, I'm confused! This thread is getting like my life - by the time I get it all together, I'll have forgotten where I put it.....

Cheers,

On another note, I believe most saw files are hardened to 60-62 Rc, but I noticed that the Vallorbe needle files are hardened to 66 Rc. I take it saw files are slightly lower to make the teeth a little less brittle when filing spring steel (usually around 50-52 Rc). How confident are we that 60-62 Rc is what we should be aiming for? Are we just following what has always been done, or is there good reason for sticking with it? Is it worth hardening some samples to 66 Rc to compare and contrast?

Just curious.

Originally Posted by Brit*al

On another note, I believe most saw files are hardened to 60-62 Rc, but I noticed that the Vallorbe needle files are hardened to 66 Rc. I take it saw files are slightly lower to make the teeth a little less brittle when filing spring steel (usually around 50-52 Rc). How confident are we that 60-62 Rc is what we should be aiming for? Are we just following what has always been done, or is there good reason for sticking with it? Is it worth hardening some samples to 66 Rc to compare and contrast?

Just curious.

An excellent question Brit*al, for which I have no answers. I thought some files are eveen harder than Rc66, but not sure where I got that idea from. I think we have all been concentrating on the corner profiles & finding files that fit the gullets they are supposed to be good for, and not mentioning the hardness factor. However, it has come up in the testing that quite a few files seem brittle and prone to severe corner chipping. Some of the brittleness may be due to poor tooth conformation rather than overly-hard (& therefore brittle) steel. Anyway, it is recorded in the test data, so something to be addressed.

If needle files are harder than saw files, it's interesting that I have not had any problems with needle files chipping the way 'regular' saw files have done. This may be at least partly due to their very fine teeth, but it probably has much to do with the better tooth conformation, too.

Cheers,

Originally Posted by IanW

If needle files are harder than saw files, it's interesting that I have not had any problems with needle files chipping the way 'regular' saw files have done. This may be at least partly due to their very fine teeth, but it probably has much to do with the better tooth conformation, too.

It's coz they got no corner teeth. They could probably be 70 Rc and the only extra danger would be easier snapping of the shaft or file body.

I arrived at 60-62Rc because of the corners. The hardness can be adjusted as we go along, no worries, just as the toothing of the files can be adjusted (and indeed the steel type). The shape of the file cannot (without significant extra cost of a new die).

Having said that, the sample file that I should receive this week is 65Rc, but I'm not too sure how critical the corners are on these file (the corners aren't toothed AFAIK, so prolly the same deal as a Needle).

Originally Posted by IanW

An excellent question Brit*al

Nah, he just wants the files to live up to his name.

Originally Posted by FenceFurniture

It's coz they got no corner teeth...

??? Wotcha mean, Brett? Do you mean they don't have regular teeth cut along the corners, as an addition to the face teeth? If so I guess I get your drift. However, the cutting of the faces raises "teeth" all along the corners on the files.

Glardon 150mm file: Glardon mag.jpg

I surmise that's how all files get anything to cut with on their corners, although some files seem to have teeth that go round & round the corners continuously, as if the file had been rotated against a cutting die, Others seem to be cut one face at a time, & the teeth on each face don't neatly match. The corner 'teeth' are just the raised edges at the ends of the face teeth.

Do you know if any files are cut continuously round & round, or am I hallucinating (again).

Cheers,

That's hilarious Brett.

How important are rounded gullets nowadays anyhow? I doubt the possibility of introducing stress cracks is as as big a problem as it once was with the steel used in new saws today, which only leaves the issue of whether a rounded gullet helps eject the dust/chips better than a pointed gullet. Since most of our issues with saws files today are to do with the edges, maybe we are putting too much emphasis on them and we should all start using the better quality three-square files.

Just stirring the pot.

Originally Posted by Brit*al

How important are rounded gullets nowadays anyhow? I doubt the possibility of introducing stress cracks is as as big a problem as it once was with the steel used in new saws today, which only leaves the issue of whether a rounded gullet helps eject the dust/chips better than a pointed gullet. Since most of our issues with saws files today are to do with the edges, maybe we are putting too much emphasis on them and we should all start using the better quality three-square files.

Just stirring the pot.

'Taint the rounded gullets per se, Brit*al, it's how rounded they are. You need to go way back in the thread to pick up that part of the discussion, but briefly, if the corner of a file has too large a diameter, it will cut a very round-bottomed gullet. That's ok, even desirable, on big teeth (the only ones I think are in an danger of stress fractures), but on small teeth, you end up with all gullet & funny little teeth (there's a picture back there somewhere illustrating this very point). I have neither the mathematical ability nor time to work out the ratio of gullet area to tooth area for such teeth, but the gullet area must be greater than tooth area, so they should carry more sawdust, & that would be a good thing, if they were all regular & even. However it's impossibly hard (for me) to make a decent job of sharpening such fangs - the slightest variation in pressure on a single stroke of the file can halve the size of a tooth!.

While it seems possible that a sharpish (I use the "ish" because no file I've ever met cuts a knife-sharp corner, & the sharpest files I know, which are the needle files I use on small teeth, make nicely rounded gullets when you compare them with the size of teeth on an 18 or even 16 tpi saw), gullet might be more prone to impaction, I am of the strong opinion that any troubles with sawdust impaction have to do with using too fine a pitch, or sawing sticky (wet?) wood than the shape of the gullet.

More stirring......

Originally Posted by IanW

Do you mean they don't have regular teeth cut along the corners, as an addition to the face teeth? If so I guess I get your drift.

However, the cutting of the faces raises "teeth" all along the corners on the files.

Glardon 150mm file: Glardon mag.jpg

Dat's roight! Let me take you back several hundred posts, to when we were debating what 3-Square actually meant, and how I was becoming more and more certain that it was being perpetually misquoted by manufacturers, retailers, and users alike. Eventually I found a site that actually defined what it meant, and it correlated with what I had suspected (after a while). The difference between a 3-Square and a saw file is nothing other than the edges of a 3-Square are not cut. A 3-S can still be tapered. They happen to be always double cut because they are always Engineer's files. The lack of edge cutting is simply so that a 3-S Engineer's file can get into the internal corners of a normal job. That is why they are not cut on the corners - to give them the sharpest (and therefore most dimensionless) corner possible. It just happens that they are now good for fine pitch saws because there is nothing else to use after the Indian vacation.

Originally Posted by IanW

I surmise that's how all files get anything to cut with on their corners, although some files seem to have teeth that go round & round the corners continuously, as if the file had been rotated against a cutting die, Others seem to be cut one face at a time, & the teeth on each face don't neatly match. The corner 'teeth' are just the raised edges at the ends of the face teeth.

Do you know if any files are cut continuously round & round, or am I hallucinating (again).

Cheers,

The corners of saw files are sharp after forging and then filed flat to varying widths depending on the file size (info provided by Peter Evans a week or so ago, and a defining moment - thank you Peter!). The corners are then toothed BEFORE the faces are toothed. On really good jobs (like your very first Liogier 4" EST Ian) they do indeed go around continuously - have a look at your pics again in my post here. (yeah, I know, the needle looks like the edges were cut, and I've wondered about that meself, but put a loupe on your current Needles and what do you see?).

Furthermore, I think you are dead right when you talk about the cut faces meeting up at the edge and forming their own "virtual" teeth.

So in effect, Engineers' files are poorly made, too, since nearly all have 'virtual' corner teeth, and will cut any surface they rub against (such as the bottom of a saw gullet)?

Originally Posted by IanW

So in effect, Engineers' files are poorly made, too, since nearly all have 'virtual' corner teeth, and will cut any surface they rub against (such as the bottom of a saw gullet)?

Yes I guess so. Remembering though, that as the files get bigger in the Engineer's range the corner will stay the same, and will only vary with the coarseness of the cut. Technically, the edges of a 3-Square are supposed to be safe so that they don't eat into that internal corner of the job, but in practice it's no-possiblè.

If Vallorbe three-square needle files are not supposed to have corner teeth, isn't that at odds with the diagram they show which to me indicates they have teeth all around.

Vallorbe1.png

Some other manufacturers show their three-square needle file profile like this which is more akin to what you are saying Brett I guess.

2.png

Funny you should mention that Andy. Those diagrams were one of my original bones of contention - too many times I have seen diagrams that contradict the descriptions (so which do you believe?). I think with the Vallorbe diagram, and the heavier dots on the edges, that they are trying to show them as uncut and sharp, but the second diagram you show is much clearer for me (showing an uncut corner). The problem is that I have seen that second diagram describing a Saw File somehwere, and I have also seen an additional "-" on the corner (as a SF should be) describing a 3-Square.

All of this just shows a lack of attention to marketing detail, and/or a lack of knowledge on the file maker's/retailer's part (I can provide the examples if needed, but it will take a little finding, although I think it might have Bahco that mixed up the diagrams. Frank - do you want me to prove it, or will you accept what I say?).

And who'd of thought that eh?

A lack of knowledge, in the current climate (i.e. sub-tropical), would be.....exactly how likely?