Drill and tap before or after heat treat?

F

fateofone

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Sep 21, 2016
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I'm pretty much positive a tapped hole is not going to stay even after a heat treatment, but will I be able to re-tap it after or will it loose some of the steel there? Basically, to tap a hole before or after heat treat?
 
You won't be able to tap it afterwards. I have tapped holes before HT, then chased the threads afterwards. Some antiscale will likely be your friend, I believe I might have used satanite as such.

What's your project?
 
As Salem said do it after, you will never tap hardened steel after heat treat, at least not with the tools we blade smiths have. But this also depends on where the hole is and how much of the blade you harden. If you are just doing an edge quench and leaving the tang soft then drill and tap after. But if that area gets hard after heat treat it ain't going to happen. I busted two dies trying to thread the stub on the end of a Damascus sword tang. I have anealed and heated and still no luck and I can file the steel. So I gave up and am cutting and notching the end of the tang for a grade 8 bolt and I will silver solder it into the slot in the tang. The head of the bolt will index in a hole so the load is not pulling on the solder joint.
 
Salem Straub said:
You won't be able to tap it afterwards. I have tapped holes before HT, then chased the threads afterwards. Some antiscale will likely be your friend, I believe I might have used satanite as such.

What's your project?
Click to expand...
I appreciate it. I'm working on a really complex knife that actually has to have screws. It's a fantasy knife. Hopefully it won't damage the threads.
 
Let's see it, need pictures.
 
Pack the threaded holes with satanite. Chase the clay out after ht.
 
I don't think you'll see as much movement as you'd think. D n' T before HT, then chase afterwards. You could always spot anneal, worst case scenario, but I really don't think you'll need to.
 
I have been pretty impressed with the ability of HT steel to hold the machining. I have never tapped holes but drilled multiple holes in a knife and everything lines up exactly where I put it.
 
No problem tapping holes prior to HT. Just make sure the threads don't get damaged before. Just chase them out after and you'll be fine.

Jay
 
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