JT6 question

[fett]

Do they make replacement inserts for the knives?

[dg]

Unfortunately, no. Some people have had success cleaning up the edges carefully with a Dremel tool or files.

[jackson1]

I have never been able to pull inserts from any trem with knive inserts. So, AFAIK you can't, but I seem to remember some members here who said they could pull them.

Won't the hardened part of the knive become soft (ruined) if you file or Dremel it? Metallurgists, please chime in.

[dg]

That's a good question. It would depend on what hardening process was used on the inserts. For example, if it was sharpened while soft, then case hardened, it would only have a very thin outer hardened layer which could be removed by the dremel or file (or already be gone if the knife-edge is in really bad shape). If it was hardened by another process like quenching, then it should be uniformly hard throughout (or at least have a pretty thick outer hardened layer), and sharpening should be OK as long as you don't heat it to red-hot in the process.

http://www.roymech.co.uk/Useful_Tables/Matter/Hardening.html

Dave or Kevin M. would be the guys to ask, but I'd bet those inserts are hardened all the way through.

[fett]

In other words. Why would anyone buy a used JT6? I will file mine down a bit with no heat. That's OK. I have 590's and OFR's all over the place.

[dg]

I don't think there's anything to lose if the edges are messed up. If it can't be saved, part it out for the big money!

[Budman68]

Actually I'm working on doing this but unfortunately I haven't finished this project yet. I've been able to slide the inserts out and sharpen the straight blade on the surface grinder at work but haven't come up with a jig to hold the radiused blade for sharpening just yet. I'm thinking a grinding stone in the milling machine, with the proper radius and angle, is going to be the best bet.

Unfortunately, when you sharpen these, you are removing the crappy chrome plating they used so if you don't keep them lightly oiled, they'll rust on you.

As for the hardening of the inserts, they seem to be hardened all the way through and not just case hardened.