Overheated maybe?

[Sealer39]

I’m making two small knives out of 1080. I normalized, heat treated then tempered the blades at 400° for two one hour cycles. I thought all was good until I tried to drill the pin hole closest to the blade which is the narrowest part of the knife. It’s too hard to drill. I repeated the temper process at 425° Then at 450° to see if that would help but it didn’t make any difference. The rest of the knife seems to be Ok, I’ve already drilled the rear pin hole on both knives, it’s just the middle of the knife that did not take the temper.

Did I over heat the steel before I quenched? Is there a way to fix this or should I toss them and start over. Thanks for any advise.

 

[Drew Riley]

You should have drilled your holes before you heat treated them, while the steel was still in the annealed state. Tempering isn't going to "soften" the steel.

If you want to drill holes after you've already hardened and tempered the blades, you'll need to use carbide drill bits, or anneal the blades again. You may be able to "spot anneal" the areas that you want to drill a hole in, but you'll need to keep the blade cool in order to prevent ruining your temper. Alternatively, you can anneal the whole blade, drill your holes, and then re-heat treat and temper, though it'd be easier to just get some carbide drill bits and drill the steel hard.

In a pinch, you can use a carbide tipped masonry bit, though the hole may end up a little oversized.

 

[Sealer39]

You should have drilled your holes before you heat treated them, while the steel was still in the annealed state. Tempering isn't going to "soften" the steel.

If you want to drill holes after you've already hardened and tempered the blades, you'll need to use carbide drill bits, or anneal the blades again. You may be able to "spot anneal" the areas that you want to drill a hole in, but you'll need to keep the blade cool in order to prevent ruining your temper. Alternatively, you can anneal the whole blade, drill your holes, and then re-heat treat and temper, though it'd be easier to just get some carbide drill bits and drill the steel hard.

In a pinch, you can use a carbide tipped masonry bit, though the hole may end up a little oversized.

Thanks for the reply. I was looking for carbide bits for sale in my area just now. These are my first two knives and I knew I’d screw something up. Lesson learned.

 

[Drew Riley]

Thanks for the reply. I was looking for carbide bits for sale in my area just now. These are my first two knives and I knew I’d screw something up. Lesson learned.

It happens to all of us at least once.