52100 drilling issues

Bill Thomas

Bill Thomas

Joined
Jul 7, 2013
Messages
64
I am a newbie and am trying to send my first batch of blades to heat treat. I have (20) 1/8 thick 52100 blades that are ground and I drilled scale holes in. This went very smoothly on all 20. My trouble began when I was drilling the thong holes. I had a new .25 bit that cut the first hole with no problem. I then ended up burning up a total of three bits on the next two blades without going all the way through. The blade did turn red but I did not think that I was applying any more pressure than normal. Can any one tell me what might have happened? I would like to get these in the mail tomorrow so that i can get them back in time for Christmas presents. Can I drill holes after heat treat? If so what type of bit do I need? Is finish grinding going to be hell on me, and my belts once back from heat treat? Any advise or suggestions on these topics would be greatly appreciated.
Thanks
Bill
 
Are you using a drilling/tapping oil as well as watching your speed? Also, I've seen Tungsten bits available on knife making supply websites.
 
I used 3n1 oil. The speed was the same as on all other holes. Is it possible to hit a hard spot on the stock or could I cause it to harden with the heat generated. I have a cheap harbor freight drill press. I'll see if I can change the belt configuration to slow it down. Thanks for the reply
 
This thread belongs in Shoptalk (knife making), not General knife discussion. Let's see if we can get a super to move it on over.
 
Run the bit slow, and use cutting fluid. 3in 1 might be ok, but rapid tap or moly d is best. Solid carbide bits are your friend as well. Light pecks and take your time.
 
Jastab said:
Run the bit slow, and use cutting fluid. 3in 1 might be ok, but rapid tap or moly d is best. Solid carbide bits are your friend as well. Light pecks and take your time.
Click to expand...

Thanks for rattling my brain Jastab. I was thinking tungsten, but carbide is correct.
 
The larger the bit, the slower you want to run.

These aren't the actual numbers, but for a .25" bit you might run 500rpm, and 1000rpm on a .125" bit. You should see clean curls or at least chips cutting pretty much right from the get-go, if not then you have a problem and should stop immediately.

I can say that with tool steel and non-carbide tooling, going really, really slow isn't necessarily a bad thing. It's much worse to go a bit too fast than a bit too slow (on most materials).

Also, ALWAYS use some type of cutting fluid when drilling/milling/tapping metal, even used oil if that is all you have. It isn't always necessary, but it takes a few years in a shop to really know when, and even then it's still better to just keep the tool cool and lubricated.



If you tell me the size and type (carbide, HSS, cobalt, moly) of the bits you are using, I can give you exact RPM numbers for tool steel.
 
I've had what sounds like the same problem on the 52100 I bought from Aldo. Some small spots in the steel seemed to be hardened. I solved this with one of three solutions: (1) move the hole a tiny bit (less desirable), (2) drill a smaller hole and then widen it, or (3) drill from the other side. Not sure why solutions 2 and 3 worked, but they got me through. It was very frustrating when the problem first came up. It was only a problem on about four holes out of almost 50 blades. I'm certain it wasn't my drilling technique or the drill bits, because my first solution was to buy a new drill bit which I immediately wrecked. I tested the inside of one of the holes with a file and it wouldn't cut. Good luck.

- Chris
 
At this point, on these holes, you have work hardened them- so perhaps carbide will get you through. I wouldn't normally recommend it though- they are expensive bits, and break quite easily. If you have an O/A torch, you can zone heat the thong tube area up to a dull red heat, not losing magnetism, and air cool to black, then quench. Do this three times, and the steel will be soft enough to drill again.

Sharpen your bit well, or use a new one, after even a slight episode of non-cutting. Nothing makes a work hardened hole worse than trying to brute your way through it with a dull bit.

52100 can be a bugger to drill- it likes to work harden, especially if not fully annealed to begin with. I find the best way is to use a normal twist drill, HSS is fine, and with the piece clamped down firmly, use the slowest speed on your drill press and give it a pretty heavy feed but back out once in a while to limit heat build up, and break the chip. Of course, use plenty of cutting fluid. I like 10% soluble oil/water in a spray bottle. The moderately heavy feed helps the bit cut, not rub- that smearing leads to work hardening. If you are enlarging a hole, don't feed quite so hard- you can blow the shoulders off your bit pretty easy. But don't feed too easy, either. You should be able to see the bit taking a chip- and a nice spiral chip is a good sign.

It takes practice! I still work harden holes now and then, and I hate it.
 
If you have a H.F. drill press and are drilling any metal put it on its slowest speed setting .If you can , get some cutting or tapping fluid . When you get ready to drill hole use steady pressure . Once you start to drill your hole do NOT let pressure off until you are through . You can (work harden ) the metal when you let pressure off . Also hard spots in metal are not that uncommon . I hope this helps . Wild Bill
 
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