What do you guys use to ream holes. I been cutting shock tabs and brackets from 4130 chromoly and it seems the holes have a slight taper. When I try to use a reamer or drill bit it is super hard on my tooling I’m guessing hardened from heat. Any advice?
I usually just use a unibit (step bit is what some people call them) on my drill press, turned down as slow as it will go.
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I have had luck with cutting the hole about an 1/8" smaller then using a drill bit to bring it to size. Seems like the bit gets “behind” the hardened layer of metal and feels easier on the bit.
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Same as what Burgs04 said. Make the hole small enough that you can cut a decent cut on the bit. Just reaming with kill your drills.
These tabs where a little better than others I cut. I was thinking about getting some carbide reamers instead of just hss or maybe even some tapered reamers
Carbide will most likely chip the corners off the bit as soon as it hits grabs the hardened metal. Try cutting the holes well undersized and drill to size. I have had success this way.
Another critical step is to make sure you drill from the backside of the part. Helps the cutting edges get underneath the hardened layer.
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Damn that totally make sense can’t believe I never thought bout that. Thanks!
The part will harden with the cutting process. Cut them under water then they will be easier to drill later
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Def seemed easier last couple i did when I filled my water table as full as I could get it
Look for Cobalt step bit or drill bits, not HSS. I have a temco step bit that has held up well against plasma and stainless.
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