Why I quit doing my own stainless: the MATH

J. Doyle said:
Also, going by the above quote, I'm not sure how much your hardness tester is going to help you.......
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You had me scratching my head on that one John. I'm a huge advocate of hardness testing because it's not uncommon at all to get surprises - whether from misidentified steel, alternate suppliers, environmental fluctuations, prior HT attempts, and so much more.

It finally sunk in what you are talking about. Travis is talking about edge quench and clay coating - and the tester needs a flat parallel surface for anything approaching a meaningful reading. Excellent point!

Rob!
 
Yeah Rob, you got it.

But I did want to point out that my statement was only valid in the context of that specific quote by Travis.

I do think that a hardness tester has definite merit. Just not for differentially hardened blades, that I can see.

To be fair, I suppose you could make coupons of carbon steels and test them if you were using an oven to make sure your oven temps were accurate and giving you the results you expected. Then you could take a little comfort that if you used those same temps/programs to differentially harden blades, you'd be in the right ballpark.
 
John, if you made sample coupons would they need to be the same angle and thickness as the part of the blade that is actually hard to get a same/same reading?
 
I actually don't think you'd get an accurate reading from any angled piece, be it blade or coupon.


I meant using flat coupons of known steel that you could test the temps and accuracy of your oven to get an Rc reading that is inline with your expectations of that steel. If you got good and repeatable results that way, you could then use the same temps/programs with your oven and the same blade steel to make differentially hardened blades and know you'd be pretty close.

That is just something you *could* do. For me personally, it seems like a lot of extra work for not much guaranteed payoff- WITH DIFFERENTIALLY HARDENED BLADES.

For me, when doing a clay hardened or differentially hardened blade, its much easier to actually do edge impact and cutting tests to ensure that I've made a good blade. Rc numbers don't do much for me on those types of blades.
 
I agree about differentially hardened blades. I mentioned previously that the flexibility to differentially harden was one of the reasons I have (or had and will have again) an oven, but the reason I have a hardness tester has nothing to do with that, for precisely the reasons John mentions. But for regular stuff with a flat cross section, I really like to be able to RC test. Example: I made a few cable billets, heated and quenched a coupon, and found that it came out around 28 HRC. No bueno. So I welded up a small san mai billet with 15n20 for a core and cable cladding. I wouldn't have known (well, in this case I might have, but still...) that such was even necessary without a tester. I also do 1095 sometimes, which I find to be somewhat finicky. It doesn't always harden completely, and I needed better data than a brass rod test or similar could provide. I'll likely occasionally do stainless anyway for one-offs, but I won't even touch it unless I have a tester.
 
A lot of good points made in this thread.....still my favorite and much truer than many of us want to admit:

"If I loved tools, and everyone should, I'd get an oven."
 Tracy Mickley

​That's a classic.....
 
Travis,
Like you, I do all of my own carbon steel blades, but have recently had some stainless sent out.
The made reason was that I didn't (and still don't) have aluminum quench plates OR a viable method of doing my own cryo treatment, at least not without spending hundreds of dollars on a dewar, and then who knows how much to have it filled.
I debated selling a few knives and buying what I needed for doing my own stainless, but after thinking about it some more, it's really not a huge priority, because I figured close to the same as you did: there's really no significant cost savings, unless, perhaps, you're doing dozens of blades at a time, or wanting to do some experimentation (aka, individually taylored heat treats).

Now, obviously the lead time MIGHT be a factor for some: Heat treating 20 blades in a day, vs a 2 week turnaround.

For the average part time / hobby maker, however? It really does make sense to contract them out, IMO. (from a cost perspective anyhow)
 
I can see both sides of this coin but for me doing 5 to 10 stainless blades a year I would end up sending one at a time. I would
not be able to hold every ones knives till I got that many so where I was sending between blade shipping and pkg to send was costing me
around 15 dollars a blade so I come out ahead doing my own on demand and my customer has no exstra wait time. To some orders they want right away
and don't mind even a little more money for the speed. So I think each way is great for you if it works the best in your shop and the way you do things. jm2c
 
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