trouble drilling holes in Aldo's 15N20

Willie71

Willie71

Warren J. Krywko
Joined
Feb 23, 2013
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I'm having an unusual problem. I have some of Aldo's thinner 15N20 (the 1/4" stock doesn't have this problem) where drilling the handle holes starts OK, then the steel appears to work harden. I tried doing a normalizing cycle to "unharden" the steel heating to 1475, then air cooling. Didn't help. I burned out three drill bits last night. Any thoughts? The last time I had this problem was using an unknown stainless (300 series.)

Thanx, Warren
 
301 stainless ?? That work hardens very quickly !!
I.m trying to get people to try a sub-critical anneal , 1200 F form 2 hours.
 
3 bits in different holes or in the same hole?


Normalizing doesn't usually help with a work hardened hole in my experience. If you're not punching holes right through like butter, you're probably not using sharp enough/high quality enough drills or enough feed pressure. But once you break one in a hole, you're better moving the hole. Especially with small bits that likely get partially lodged in the hole, and will help break the next bit.

I've got a bunch of Aldo's 1/8 15n20 and I haven't had any problems with it.


Mete's suggestion of a sub crit anneal is prob a good bet short of doing a full anneal.
 
I have a good set of HSS bits from Lee Valley that have worked very well for me, way better than the cobalt and Ti coated stuff from the hardware store. I tried those bits as well, and they burned out faster yet. It was all three holes that had problems, and I had a previous knife with the same issues from the same bar. I thought the normalize might not to anything. I'll try the anneal on the next one and see how that works. I had no trouble with the 1/16 or 1/8" stock. I got some of the surface ground stock in 0.9 and 0.7 approx and that is the steel I am having trouble with.
 
Hmm well, I dunno man. There are of course, always variables that affect your methods when boring.

What size holes are we talking? I break bits usually before I ever experience dullness/burning them personally. More often than not it's because they'll pull a chip that's too big for the high hardness of the ones I use, and the mill will shatter the bit.


I'm guessing the issue is feed. And if we're talking bigger holes (like 1/4 or bigger), you prob need to drill an undersized hole first with a fresh 1/8th bit.. Still, I have no experience with this particular size of Aldo's 15n20 stock, so maybe it's just not annealed correctly. You having any trouble with sawing it?
 
You are probably trying to drill at too high a speed. That's what work hardens the steel. Try going dead slow speed w/ medium pressure and some drilling and tapping fluid.
 
It's not drill bits or drilling speed.

1.) You heat 15N20 into austenite and air cool, it will air harden like a big dog. You can harden 15N20 by plate quenching. Just air cooling will harden it enough to smoke any drill bit you have in the shop.

2.) Do what Mete says - soak in the oven at 1200-1250 for about 2 hours. This will be a spherodizing anneal and it will cut like, well, annealed steel. At the end of 2 hours, pull from the oven and oil quench and drill all the holes you want.
 
Karl B. Andersen said:
It's not drill bits or drilling speed.

1.) You heat 15N20 into austenite and air cool, it will air harden like a big dog. You can harden 15N20 by plate quenching. Just air cooling will harden it enough to smoke any drill bit you have in the shop.

2.) Do what Mete says - soak in the oven at 1200-1250 for about 2 hours. This will be a spherodizing anneal and it will cut like, well, annealed steel. At the end of 2 hours, pull from the oven and oil quench and drill all the holes you want.
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Makes sense to me. I'll report back on the next one.
 
Forgot to mention. The "problem" steel is surface ground to thickness. Th steel with mill scale is fine. I suspect the surface grinding generated enough heat to partially harden the steel.
 
Air cooling it is too rapid, as 15n20 can air harden to a degree. Get a localized heat with a torch and and slow cool it by shoving in a pile of vermiculite or kitty litter.
 
Frank Niro said:
Carbide drill bits will work fine . Frank
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I'd be surprised if they didn't.

Search youtube for "ultimate drill guide" I think. Very well done and informative videos on the capabilities of the different types of drills. Regardless of work hardening, if a carbide drill won't penetrate it (assuming proper speed, feed rate and lube) there's gotta be something else happening. I've broken far too many drills lately, mostly hss, so I'm keen to finding a solution too.
 
Artu brand drill bits. They'll eat through it like butter and make carbide bits look like toothpicks. No need to anneal or any of that.
 
Gentlemen,
The 15N20 you have all been using in Damascus is typically from coils of pre-hardened material(42Rc.) for the band saw industry. Some of our stock is from the same. Our 1/16 and 1/8 is rolled and annealed for us. As the other stock we have gets used up we will be replacing it with this annealed stock. It is much easier to work with if you want to make knives with it and it actually brings up a pretty nice Hamon as well. :)
 
Well, that explains a lot. I bought some from Tracy a while back and they said they got it from Aldo. It smoked every bit I threw at it. I've never had a problem drilling any steel before, but my four pieces are just rusting now. I don't have an oven to anneal it so it's pretty much worthless to me. Kind of sucks not knowing, but I guess that's what I get for assuming the steel I bought was annealed already. Lesson learned.

Aldo, when do you anticipate switching completely to annealed stock? I'd love to try some 15N20, but I'm not going to buy any until I'm sure it's soft.
 
Altofsky said:
Artu brand drill bits. They'll eat through it like butter and make carbide bits look like toothpicks. No need to anneal or any of that.
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What material are the bits made of that they outperform carbide so seriously?
 
Here you go. From their ad.
" The Artu multi-purpose drill bit is made of top quality chrome vanadium steel shanks for enormous strength, topped with an extremely tough cobalt and tungsten carbide tip designed for maximum hardness, and resistance to heat and wear. This revolutionary new hole drilling system enables the user to efficiently bore holes in a wide variety of materials with a single multi-purpose drill bit."

Apparently, they say they will even drill through glass. A 13 bit set costs about $65 or so.
 
They are steel bodied carbide tipped bits. The tougher body reduces breakage, the carbide cuts almost everything. Carbide bits are good, but have to be used right or you will throw a lot of dollar bills in the trash can. Clamping the work solidly is the first requirement in using carbide bits.
 
They don't actually cut anything. The tips of the bits are grinding surfaces rather than cutting surfaces. You can see this as you use them. No neat spirals of steel coming off as with a nicely sharpened drill bit that cuts well. Just ground off shards come off the bit. Grinds the steel to dust, really.
 
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