Thread: Dovo Mfg video....

Originally Posted by majurey

Cheers Randy, I really enjoyed that. Two things I found remarkable:

[1] At 3.38 there's some serious hammering on the blanks. Which made me wonder... if the guy can hammer away at blanks like that, why is it a little ding on my faucet ends up cracking the blade?

I'm still downloading the video, but Randy's probably right. There is a HUGE difference in what you can do before hardening vs. afterwards. Yesterday I forged a knife blade by hammering on it for an hour and a half. I heat-treated it and it developed a crack in the edge. So I set it on my anvil and gave it a rap with my hammer. The blade snapped cleanly in two.

Razor blades are extremely thin and hard after heat-treating, which is why they sometimes shatter if we drop them.

Josh

Edit: Just re-read Randy's post, and he was exactly right, as usual.

Just watched the video... Actually, it appears he was hammering on them after heat-treating. But they weren't ground to the final thickness yet, which would make a difference.

It looks like they use salt pots for heat-treating. Interesting.

I had to laugh when I saw that lady do a hair test with the razor she had just honed. That looked like a bristle from a paint brush. I could probably pass that test coming off the DMT 325.

They're also using disc grinders to set the bevel, much like the TI factory.

Excellent video--thanks, Randy!

Josh

Originally Posted by JoshEarl

It looks like they use salt pots for heat-treating. Interesting.

They're using lead (I think TI does too) at over 850 C for four or five minutes (the guy who does it compares it to boiling eggs ) and then into some sort of oil.

Heres a question. When the lady is honing back and forth on the stone, she "slices" the blade through some metal block. What in the world is that?

Originally Posted by IsaacRN

Heres a question. When the lady is honing back and forth on the stone, she "slices" the blade through some metal block. What in the world is that?

Looks like a piece of thick leather .. I'm guessing it's to possibly take a wire edge off .. I'm more than likely wrong .

Garry

Originally Posted by bjrn

They're using lead (I think TI does too) at over 850 C for four or five minutes (the guy who does it compares it to boiling eggs ) and then into some sort of oil.

That was actually my first thought, but since TI specifically advertises it's blades as "lead-hardened," I assumed Dovo would advertise it, too, and my next guess was salt pots. That's what I get for not speaking a word of German.

My understanding of the lead-hardening process is that it's done after the blades are mostly ground, since the lead doesn't oxidize the blades like many hardening processes would. Dovo seems to do all of the grinding after the blades are hardened, which would seem to me to negate the advantages of using lead. Unless they just think it makes for a harder blade.

Josh

i must say, my german sucks. i did not understand any of that. another semester of high school 17 years ago down the drain. crap.

very cool video though. i used to work in a manufacturing plant. to see the raw materials all the way through to the finished product is pretty amazing. thanks for the vid.

vgod

Great video. Thanks for your efforts. It's amazing what a relatively small factory can produce.

When this vid first became available someone who knew German said that Dovo is using molten lead for heat treating. Using molten lead would reduce the amount of carbon lost during heat treating, molten salts would accomplish the same thing. The quenching is done in oil. They are not showing the tempering process which makes the steel less brittle. The steel is still not ground thin at this point thats why they can whack it with a hammer to reduce any warpage without breaking the blade.
They should be normalizing the steel before heat treating but that step is not shown. If they are not normalizing the steel and combined with the actions they use during quenching, the swishing of the blades in the oil, would go a long ways to account for the warping of the blades.

I do want one of those hollow grinders!

I speak quite a bit of german, If you have any specific questions I will try to translate parts of the video. I wont be availible for the next two days though so just post your questions and I will get back to you.

Brandon