Tang Hole Help Needed!! 5/16" Holes in 1080

A

ADHD426

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Dec 9, 2013
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I have profiled my first knife. I am trying to put 5/16" holes in the tang, 5 of them to be exact. I went and got a 1/8 and 5/16 cobalt drill bit. The 1/8 went through like butter. The 5/16 took a lot of coaxing and it finally went through but I am 99% that bit is dead now as I tried another hole on a scrap and it would not cut. I am using a drill press and tried both 700 and 1000 RPM. Should I be doing for pilot holes to step up or should I be able to go from 1/8 to 5/16? The holes are in 1080 steel @ 30 Hrc. Any tips on how to get my tang holes? Thanks!

Andrew
 
You can run the 1/8" drill at 700 if it is sharp, maybe even a little faster. I wouldn't run the 5/16" any faster than about 400rpm in that material. The 1/8" pilot hole is fine but if you get a lot of heat build up the material will work harden and getting the larger drill through will be a challenge. You should keep a bottle of oil at the drill press and use it. The twist drill can be re-sharpened.

Bob
 
You'll probably need to spot anneal that hole now. If this happens to me, I use a torch and heat the area to a dull red, still magnetic, air cool to black, quench in oil- repeat three times. That will soften up your surely work hardened hole. Then, take a SHARP bit, with the lowest speed you can drill at, and feed the bit in hard with cutting oil. You don't want that bit rubbing the surface of the hole all over again, you want it to break past the still somewhat hard skin where your ruined bit smeared it.

Sometimes flipping the tang over and trying to drill from the other side can help, but still do the anneal, and still use a sharp bit.
 
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