Saw File Hardness Measurements

**FenceFurniture** · 19th May 2015, 07:43 PM

Originally Posted by rob streeper

1) Uniformity of toothing Ah, wassat? Must be like that weird QC thing.
2) Is a less appropriate alloy being used? No doubt - even if it was of the same class steel, it's of Indian etc origin.

Question: can steel of the same hardness be of different brittleness (as a result of hardening tempering differences) or can that only be possible if it's a different type of steel? I ask because teeth snapping off seems to be a big complaint, even with better files such as Bahco.

**BobL** · 19th May 2015, 07:48 PM

Originally Posted by FenceFurniture

Time isn't really a factor Bob. Of the current lousy standard, one file is lucky to sharpen 2, perhaps 3 saws - essentially using one corner for a saw, and may have to break into the second corner to finish it.More usually though, one file can't even sharpen one saw.....

Ain't no such thing as an old (still in use) saw file - not these days anyway.

OK that makes it very easy then because user perception already includes a component for longevity.

High magnification on the teeth may reveal something very interesting.

My hypotheses are
Files that are too hard break teeth and are less effective
Files that are too soft go blunt and are less effective
The files that are tougher (resist abrasion and tooth breakage) last longer and are more effective.

**rob streeper** · 19th May 2015, 07:48 PM

Originally Posted by FenceFurniture

Question: can steel of the same hardness be of different brittleness (as a result of hardening tempering differences) or can that only be possible if it's a different type of steel? I ask because teeth snapping off seems to be a big complaint, even with better files such as Bahco.

It is possible to ruin steel by overheating it even if it started out as a 'good' alloy. Other bad things can be done such as using the wrong atmosphere during manufacturing or heat treating, working the steel at the wrong temperature and so on. Mechanical factors come into play as well.

Snapping of teeth is something I hope to address, at least partly, with cryogenic treatment. I have a box of files that seems particularly prone to tooth loss in use and it would be a simple experiment to do, just gotta find the time.

**rob streeper** · 19th May 2015, 07:50 PM

Originally Posted by BobL

OK that makes it very easy then because user perception already includes a component for longevity.

High magnification on the teeth may reveal something very interesting.

My hypotheses are
Files that are too hard break teeth and are less effective
Files that are too soft go blunt and are less effective
The files that are tougher (resist abrasion and tooth breakage) last longer and are more effective.

My mechanical Turk will tell an interesting story about toughness.

**FenceFurniture** · 19th May 2015, 07:56 PM

Originally Posted by rob streeper

It is possible to ruin steel by overheating it even if it started out as a 'good' alloy. Other bad things can be done such as using the wrong atmosphere during manufacturing or heat treating, working the steel at the wrong temperature and so on. Mechanical factors come into play as well.

You must mean like this (out of the box - never used - dunno why)

:

**rob streeper** · 19th May 2015, 07:58 PM

Originally Posted by FenceFurniture

You must mean like this (out of the box - never used - dunno why)

:

Amazing picture. The QC manager must've been tied up in a broom closet while that batch was being made. Who pray tell is the manufacturer of this illustrious example of the file makers art?

**FenceFurniture** · 19th May 2015, 08:01 PM

Originally Posted by BobL

OK that makes it very easy then because user perception already includes a component for longevity.

Yes it does, particularly because even the very best saw files from yesteryear had a quite short life. This is because it's the corners that do virtually all the work, so there's an excessive amount of wear that the faces don't get.

As a result of such a short working life it's very easy for the operator to make a valued judgement on whether the file is any good or not for longevity - it's not like they have to remember if the previous one lasted for 6 or 12 months. Merely a matter of hours (or minutes, these days

).

**FenceFurniture** · 19th May 2015, 08:09 PM

Originally Posted by rob streeper

The QC manager must've been tied up in a broom closet while that batch was being made.

There you go again, making assumptions

How many times do I gotta tell ya - think like an accountant - who's the first guy to give the chop so you can drive a better car?

Btw, the whole box of 10 or 12 was like that. The Pferd distributor in Melbourne was deeply embarrassed when I emailed him the pics. So much so that he sent up 3 replacement boxes, and sadly they were all crap for a different reason (but they didn't put a fish hook gullet in the saws

). I sent you one of the replacements (which is the same as the worn one you have just hardness tested - from the same box/s)

**rob streeper** · 19th May 2015, 08:15 PM

Originally Posted by FenceFurniture

... think like an accountant ...?

I can think like an accountant, I simply prefer to avoid it if possible.

Accountant sees: I gotta whole huge pile of damaged mill heavings to dispose of and it's going to cost big bucks because it's hazardous waste - full of heavy metals.

Accountant solves: I know, let's make some files and get people to pay us to dispose of our waste! Big bonus check!

Now I feel dirty.

PS. Probably should say 'plutocrat' not accountant. I have known some decent accountants.

**rob streeper** · 19th May 2015, 08:26 PM

Originally Posted by FenceFurniture

There you go again, making assumptions

How many times do I gotta tell ya - think like an accountant - who's the first guy to give the chop so you can drive a better car?

Your reference to cars strikes a chord with me. A while back I had a young engineer tell me of the plight of a friend of his. Both of these guys took their degrees from a university which is reputed to be one of the best if not the best in the world. Seems the first job after graduation of this friend was at a major US car manufacturer. His task was to take the product line and redesign each of the components such that the mean time between failures was just longer than the warranty period. Sad what the world has come to.

**BobL** · 19th May 2015, 10:10 PM

I threw the camera on the macro stand and just took these - They is half full size resolution. DOF or sharpness not optimised.

The files were briefly cleaned with a file brush.

This a new file I use for plastic only
Saw File Hardness Measurements-file1-jpg