Recommendation? Drilling Stainless San Mai?

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RedCrow

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Dec 24, 2018
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Hey guys. Hopefully this isn's a stupid question. I made a few stainless san mai knives and the first one went well. It was 304 stainless from a local welder for the cladding and a core of 1084, and the holes for the handle pins drilled right through without a problem. I tried again today, using 52100 and 410 stainless from Jantz. this time, no drill bit I have will even touch the stainless. 304 is supposed to be moderate machining stainless, and 410 is supposed to free machining, so it should have been easier to drill into the 410. Is there something I'm missing, or did wrong?

If 410 is ALWAYS this hard to drill, is there a particular type of drill bit that people are using? I see a ton of people using the 52100/410 combo, so I know it isn't a bad choice of materials. FYI, the knife is a total thickness of about 3/16 now, with the roughly equal sides and core, so the stainless portions should be roughly 1/6 inch each. It really shouldn't be this hard to drill them, unless I'm missing something. Thanks in advance for your help. Have a great day!
 
410 is NOT free machining ! but 416 is . free machining steel has higher sulfur to do that .
Work hardening is a problem with many SS alloys so do some research on drilling to minimize work hardening .
 
Try annealing at 1350 degrees for two hours and then let cool overnight. It helps to put some large pieces of metal with the blade so it cools slower. I learned this from Ed Caffery. It works.
 
you can also try and anneal of heating to dull cherry red or that 1350 and slow cool anneal in vermiculite or wood ash.
I've never had a problem drilling thru the 410 cladding
 
Tom Lewis said:
Try annealing at 1350 degrees for two hours and then let cool overnight. It helps to put some large pieces of metal with the blade so it cools slower. I learned this from Ed Caffery. It works.
Click to expand...
There is no need to slow cool steels when doing a sub-critical anneal. The spherodizing is taking place while in the oven at temp - not while "slow cooling".
At the end of the cycle just remove it from the oven. When it cools off go to work on it.
 
Karl B. Andersen said:
There is no need to slow cool steels when doing a sub-critical anneal. The spherodizing is taking place while in the oven at temp - not while "slow cooling".
At the end of the cycle just remove it from the oven. When it cools off go to work on it.
Click to expand...

I agree, I often work on the blade out of the ash after an hour or so.
 
304 is an Austenitic Stainless Steel and cannot be hardened by heat treatment. 1084 is a fairly simple steel that needs a fast quench (in Water or, for thin sections, a fairly fast oil): if you do not actually try to harden it, there is effectively no chance that it will get hard. With your earlier SAN Mai, all you'd need to deal with for drilling was work hardening.

As far as I can tell, Jantz do not sell San Mai, so I assume you have welded and forged the San Mai yourself.

410 is a Martensitic stainless steel and is air-hardening in thin sections (like yours).

52100 is an oil-hardening steel, which gives about 4 times longer to pass the pearlite nose than 1084. (I know from my very limited personal experience that O1 has an annoying habit of air-hardening if you are careless, but O1 gives about 3 times longer to pass the pearlite nose than 52100. It does not seem very likely you'd harden 52100 by accident, though I don’t know enough to rule it out).

If you didn't actively take steps to stop it hardening from the forge, your newer San-Mai will have hard outer layers and may, just possibly, have a hardened core layer. It would almost certainly benefit from normalisation (to reduce the grain size from welding and forging), and an anneal will be necessary unless you are equipped to drill it in the hard condition (either a full anneal or more likely a sub-critical anneal, depending on what else you intend to do with it).
 
I'd just take an Oxy acetylene torch, and carefully run that part of the tang up to a very dull red heat (12-1300f) and let air cool to black, three times. Be careful not to bleed heat into the blade. Then I'd temper the remaining part of the tang, up to the shoulders, to blue as well.
Should drill fine after that.
But, my favorite is to just drill with a carbide endmill for pins anyway. A carbide drill bit would be fine too, I just hae the small endmills on hand anyway for slotting guards and the like...
 
Thanks a lot for the replies and the help. I did try annealing it by heating to 1000 and allowing it to slow cool in the heat treating oven, but that didn't do anything to help. I'll try one more time at the 1350 several of you have suggested, and I'll get some carbide endmills ordered as well. Thanks again.
 
I find this very interesting. Karl Anderson said,
"There is no need to slow cool steels when doing a sub-critical anneal. The spherodizing is taking place while in the oven at temp - not while "slow cooling".
At the end of the cycle just remove it from the oven. When it cools off go to work on it."

I looked this up in a metallurgy book and the book said slow cooling was NOT needed. I have always been told slow cooling was necessary. So I think I just learned something.
 
I would never use an austenitic stainless for cladding. There will always be some carbon migration to the cladding and some alloy migration to the core.

Austenitic stainless becomes martensitic stainless when carbon is added. Martensitic stainless with high nickel content is almost impossible to anneal. 410/416 is a lot less problematic when used as cladding. Careful annealing is still needed.

Hoss
 
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