Is a file's hardness skin deep?

Re: Is a file's hardness skin deep?

joel

>Bill,

If you recall this was the gist of my post on a thread on rasp sharpening a few weeks ago.

I am glad to see my information born out in experimentation.

If a rasp or file was hard all the way through it would crack in use. That's why they are case hardening.

58RC sounds a little low - a quick test of some rasps here at the surface puts them above 60 but I would guess there is a variation between batches etc.

Re: Is a file's hardness skin deep?

Joe Rogers, Northern Virginia

>That is an interesting bit of detective work. Good job Bill.JR

Re: Is a file's hardness skin deep?

Todd Hughes

>I don't know why you didn't but You should have tested up on the file further where the teeth are and not back toward the tang area. I think if you have done this you would have found that the file was hard all the way though.In my experance file's tangs and the area past the teeth are softer then the file body itself where the teeth are just the same with quality knives.If you ever used one of those screw on file handles you will see where it actually cuts threads into the files tang to hold it on so you can see this area of a file is softer.What your test shows not that the inside body is softer or that a quality file is case hardened but only the tang end is softer in the center. This is probably the result of like in knife making this area was not heated as hot when tempered,[probably held in a clamp during heat treating] so that it would stay softer.This would also explain why on the end the outside is somewhat harder then the center because it would be hotter when tempered.This was just how I made knives as well.Just like with a knife you don't want a file to have a hard tang as this is an area that could cause it to fail.....Instead of grinding the top surface off which could lower the hardness if it over heats why don't you just snap a file in two and test the center where it breaks.Of course if the center a file is soft you might have trouble snapping it in two....I never had any trouble though....Todd

Re: Is a file's hardness skin deep?

bill tindall

>If you will send me a $50 Nicholson pattern file that I may break I would be glad to repeat the experiment.

The test area was next to the teeth, 1" up the file from where the tang began and 2" from the bluish area where the tang was softened. The surface of the test area was Rc 58. So it would seem that your objections to the test area location are unfounded.

Re: Is a file's hardness skin deep?

Jonathan Peck - N.Y.

>I have to admit that these findings have gone over my head somewhat. But in the interest of settling this, for which I am curious of the result, I gladly volunteer to stop by Tools and give Joel fifty large if he'll send Bill a Nicholson file to perform this test.

If you wanna make this interesting, I will accept a small handtool (prefferably homeade) in return for my gifted fifty from the person with the incorrect answer.

regards

Jonathan

Re: Is a file's hardness skin deep?

Todd Hughes

>email me your address and I will send you a Nicholson file to snap in two to test, no trouble.....Todd

Not sure

Bill Houghton, Sebastopol, CA

>This conflicts somewhat with my experience of breaking a file with a hammer in my youth - it seemed way too brittle for Rc38.

Re: Is a file's hardness skin deep?

paul womack

>In my experance file's tangs and the area past the teeth are softer then the file body itself

In new (or "as new condition") files, there's often a clear band of tempering colours, normally around the shoulder where the tang starts.

BugBear