Heat treat and flatness

[john april]

great idea sando.

 

[Quinn406]

No, it would not work, as the blade will be in a foil packet.

I think you are overthinking this. Make some blades and see if you even have a warp issue. You are going to have to make a good number of blades to learn the process, anyway.
Try the blades:
1) Completely done with .003 extra for finish grinding/polishing.
2) 50% done.
3)Leaving a section along the spine that is full thickness (to be removed after HT).
4) As a profiled blank.

I didnt post the response about milling the negative into quench plates, Yeah im thinking ill most likely end up going with number 4 and just mill it hard. It will eliminate extra fixturing steps at a small cost of needing to rotate carbide inserts more often. Toroid inserts can be rotated like 10 times so ill get a ton of use even milling hard.
As for the vertical vise quenching, that will be perfect for me since i have a nice kurt machining vise. The plates can be bolted on just like soft jaws and they will tighten together perfectly parrallel.

 

[Alex Topfer]

how smooth can you get the milled bevel? i would worry about ridges from machining, although i suppose you can solve that with correct fixturing

(the idea you need to hand make a knife is kinda funny when people then turn around and say you need the ultimate precision heat treat. which one is it? )

 

[A.McPherson]

Alex Topfer
That's what you get when you buy a custom, hand made knife. Greater attention to the details, like a precision heat treat.
Factory made knives don't have optimal heat treats, because optimum is so close to failure. Higher harness equals higher failure rate. So factories tend toward softer blades so they have a lower failure rate.

 

[Quinn406]

how smooth can you get the milled bevel? i would worry about ridges from machining, although i suppose you can solve that with correct fixturing

(the idea you need to hand make a knife is kinda funny when people then turn around and say you need the ultimate precision heat treat. which one is it? )

Pretty darn smooth. Ill be using a toriod style cutter, 25mm diameter with 5mm radius. Its a 3d machining tool path, cam on fusion360. Step down of a few thousands. Ive done quite a lot of 3d machining but mostly in aluminum. Large molds for prepreg carbon fiber parts. Hardened steel is something entirely different but really not that much. Small fraction of the surface speed. Could potentially be over an hour to do a bevel depending on step down, surface speed, chip load, etc. Nice part about cnc though, load a pallet of blades and let it go for many hours while you work on other stuff. 3d machining isnt the only option though. Grimsmo does the rask blade with a simultaneous 5 axis tool path on his kern. The machine articulates the blade as the edge of the tool follows flat against the bevel. Even in that case he does grinding afterwards though. The norseman on the other hand has those intentional tool marks which is very convenient to produce.

 

[Scaniaman]

Everything Stacy said.

On the topic of warping and using plates, warping plagued me until I discovered the issue.

Don't set the blade on one plate and then fiddle-fart around getting the second plate on top with a clamp. Seems one side started hardening on me before the other, because every blade warped some. I always had to straighten what I could then grind flat.

So now I have the plates mounted vertical in a vise. Drop in the packet and crank it shut.

View attachment 1692605

I have a similar but free floating approach, with two aluminium blocks and a couple of 450 lbs speed clamps. I like it, and it lets me take the plates to cool off in cold water when doing multiple blades.