file test or other means

[jdale]

My latest knife made 100 cuts through 3/4 sisal rope and still shaved arm hair, but slightly divited when i cut through bailing wire. I am assuming its somthing to do with the quench.
I cant seem to convince myself weather or not my blades are passing the file test after quench. Does anyone know if there is a video out there on the web of a file test tutorial, or another non destructive test method to test for a successful HT?

[metal99]

I'm no expert here but I have noticed that the file test isn't all that accurate really. It's just showing that your knife is harder then the file. I did some tests on o1 and 1095 my files would honestly get wrecked from trying to file the steel on all the tests. But when I did some wire cutting some of the test pieces would chip some wouldn't do anything and others would roll an edge or indent and they all passed the file test.

I read in a few places and I know I'm going to get this wrong but I read something that said a piece of steel can pass the file test even if the HT is wrong. It's got something to do with the soft pearlite being surrounded with carbides? Does that sound right? So when you file it the steel seems hard but in between the hard carbides there can be soft pearlite. I guess that would make the file skate over the carbides but the wire is small enough to move the pearlite.

Sorry if I got that all wrong I'm still trying to wrap my head around this stuff.

[WBE]

"I read in a few places and I know I'm going to get this wrong but I read something that said a piece of steel can pass the file test even if the HT is wrong. It's got something to do with the soft pearlite being surrounded with carbides? Does that sound right? So when you file it the steel seems hard but in between the hard carbides there can be soft pearlite. I guess that would make the file skate over the carbides but the wire is small enough to move the pearlite.

Sorry if I got that all wrong I'm still trying to wrap my head around this stuff."

You are pretty much right on that. This most often happens with 1095 and similar steels if your quench medium does not cool fast enough to beat pearlite formation. With 1095, that is less than a second. Close to a 1/2 second for max hardness.

[jdale]

I was using the 1095 but ended up getting 1075/1080 from admiral steel and im using parks 50, so i know im not forming pearlite. When you test with the file do you use the flat of the file or its corner?
I have tried every variable to this mystery called heat treating and it feels like im spinning my wheels.
I need to find a semi local class or a maker around here and get a base line for what im trying to do, from my memory of blade making class i attended in my youth he never instructed us on testing the blade post HT.

[Recurve]

jdale, I purchased some 1075/1080 from Admiral a few years back and really varying results if they can't pin down if it's 1075 OR 1080 then it's difficult for us to figure out a reliable heat treat for it. IMO next time you order steel get some from Aldo it's a bit more expensive but, I believe you will like the results better. just my $.02 -Jim-


www.shullhandforgedknives.com

[SVanderkolff]

If you search on ebay or other similar site you can often find the hand held rockwell hardness testers. This will largely eliminate any doubts. If you get one just make sure it has the diamond penetrator.
Steve

[Ray Rogers]

QUOTE: I am assuming its somthing to do with the quench.

Maybe not, could be the temper. If by 'divot' you mean a small chip popped out then raise the tempering temperature by 25 degrees. If you meant the edge folded a little but didn't lose any metal then lower the temp by 25 degrees...

[jdale]

Originally Posted by Ray Rogers

QUOTE: If you meant the edge folded a little but didn't lose any metal then lower the temp by 25 degrees...

if this was the case would i have to start the ht all over or could i re temper?

[Ray Rogers]

To lower the temp you'd have to do the HT over. Something to try on the next knife though ....

[Doug Lester]

If you want to get a hand held, or a bench mounted unit for that matter, you will have to make sure that it will measure hardness in something as thin as a knife blade. Finding one that will measure hardness in work 2" thick is easy. Finding one that measure steel down to 1/8" or so is a whole different matter. While researching hardness testers I found a unit that only measured down to 5MM, somewhere around 3/16" and it ran more than $2000, as do new units that will measure down to about 1/8" .

One thing that I read about some of those used units, such as the Ames models, is the reason that they are listed on Ebay is that they are so old that the manufacturer will not longer support them. Personally I think that this is a real neat way of making people replace functional equipment but, that aside, it also means that when you need that piece of equipment worked on down the road you won't be able to get it done and you'll be looking at spending another $1200-$1400 on getting another used unit.

As far as the indentation in the edge of the blade when doing the bailing wire cut test, the results will also depend on the edge geometry. A thinner edge with less steel behind it can flatten a little with this test. If you are getting 100 cuts through a rough fiber rope and it will still shave hair I would say that you have adequate hardness for edge retention.

Doug

[metal99]

I agree with Doug on that one ^^^

[jdale]

Hearing that does make me feel better. With as much as i have been worrying about my ht i think im going to start saving up for a paragon ht oven

[Doug Lester]

J, that sounds like a good idea. Saying that you can have too much heat control is like saying that a cabinet maker can have too many clamps. Yes, you can heat treat simpler alloys just fine in a gas or solid fuel forge if you pay attention to your heating. It also helps if you learn to spot decalescence and recalesence. However, especially where you need to soak at temperature for any length of time, something like a heat treating oven or a molten salt pot can make your life a lot easier.

Doug