Drilling 5160

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Jan 8, 2015
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This is probably a stupid question, but if I find the answer I'll be gratful and a little less stupid.

I've run into and issue drilling 5160. It's all annealed new steel, but when I attempt to drill 1/4" holes I get varying results. Sometimes it cuts like butter and other times I drill about a 1/16" of an inch and it acts like it's hardened. I've even moved to another part of the same piece of steel and drilled right through it. I've drilled 1084, and 1095 and old annealed files with no issue. The only other time I run into this is with leaf spring. I'm running my current drill press as slow as it will go. Off hand I'm not sure of the speed. I'm using cutting oil. Is the steel hardening as I drill?
 
Could be a dull bit,have you tried a starter hole 1/2 size ?What do the chips or curls look like?
 
Best gem I picked up so far on drilling any tool steel or alloy steel, annealed or hardened; Masonry Drill Bits!!!!
 
'Leaf spring' ?? so you don't know what you have !! In the past you could guess fairly well for certain parts but today it gets more difficult .The other thing is HT . What is the HT you have to guess there also.
Best start here is to sub-critical anneal , 1200F for two hours .
 
'Leaf spring' ?? so you don't know what you have !! In the past you could guess fairly well for certain parts but today it gets more difficult .The other thing is HT . What is the HT you have to guess there also.
Best start here is to sub-critical anneal , 1200F for two hours .
I thought I was pretty clear that I was using new, annealed 5160. The only other steel I have found that was difficult was leaf spring. Anyway, I was recently informed that my drill press is too fast (at around 600 rpms) and that the 5160 is hardening under the bit. So I barrowed the use of a better quality press that turns at 300rpm and that seemed to take care of the problem.
 
That 1200 F covers a lot of problems even though I misread the post.
While speed is important so is feed rate ! If feed rate isn't high enough that invites cold working . So it should be slow speed , high feed , lube , sharp drill .
 
mete is bringing up a good point. How hard you push in drilling is important. Many people press very lightly, thinking it is less friction. But, it actually hardens the steel faster because of the slip. I use a pecking motion, In hard and up, in hard and up. That and tap-matic work most every time.
 
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mete is bringing up a good point. How hard you push in drilling is important. Many people press very lightly, thinking it is less friction. But, it actually hardens the steel faster because of the slip. I use a pecking motion, In hard and up, in hard and up. That and tap-matic work most every time.

Stacy, Is there a metalergic reason I'm having a hard time with 5160 or is just poor technique alone? I will apply your method as soon as I have an opportunity. Thanks
 
That 1200 F covers a lot of problems even though I misread the post.
While speed is important so is feed rate ! If feed rate isn't high enough that invites cold working . So it should be slow speed , high feed , lube , sharp drill .
Slow speed, high feed...that is a real big part of my problem up to this point. Thanks
 
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