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Drill bits for forged and billet 6061 and or 7075 aluminum

BKyle

Plastic
Joined
Apr 3, 2021
I have recently been doing some gunsmithing and building from 80% aluminum receivers.
They are either forged or billet 7075 or 6061 receivers and looking for some recommendations on drill bits that work the best in this type of material.
TiN coated bits were recommended buy a few folks but wanted to get some input on what others have used to drill clean holes in aluminum.
Any info would be greatly appreciated.
 
What I do on 80% receivers is to drill a bit under-sized holes (never trust a drill bit to make a round hole or be "accurate") and follow with the proper size reamer. Brand of bit doesn't make much difference this way as long as it's reasonably straight. IMO it's the best way to get good results.

FWIW

-Ron
 
I like TiN coated stub drills on steel, but they suck when drilling aluminium on my small CNC, the swarf seems to bind to them more readily. So I'll echo the recommendation for bright or steam tempered.
 
NIST has published material sheets that describe various metals and how they are best machined. The one for aluminum is here: https://materialsdata.nist.gov/bitstream/handle/11115/200/Machining of Al.pdf?sequence=3&isAllowed=y

When drilling a material, to get the best possible result you should determine the optimum rake and relief angles for the material and feeds you are using. Insight into these two angles can be gathered from the aforementioned material reports.

Once you know the angles, take standard HSS metal cutting drill bit and grind the rake and relief into the tip of the drill bit. You will then have an optimum tool for your drilling operation.
 
If you are drilling through a steel or annodized guide it will be hard on the drill tips causing burrs on exit especially given the quality of the average drill press these days
 
Amazing and good information from all of you and really gives me a different perspective on just what drill bits to use. Most of jigs for these receivers use drill guides so I had never toyed with the idea of drilling undersized and reaming to correct size.
 
Bright finish HSS. Sharp and fast

This, there is no need to spend money on fancy drills working in 6061 or 7075 unless you have an excessive depth to diameter ratio. Unless of course you are trying to machine crappy Chinese 6061, then all bets are off.

P.S. Refrain from buzz words like billet. I can't believe it took till post #8 for a comment.
 
Gunsmithing, Aircraft piloting. Horse riding. Video game playing. Drinking, especially in nightclubs. Mainlining heroin. All activities in which I'm dead thankful I never took an interest.
 
Gunsmithing, Aircraft piloting. Horse riding. Video game playing. Drinking, especially in nightclubs. Mainlining heroin. All activities in which I'm dead thankful I never took an interest.

Horse riding isn't bad, it just isn't as easy as the experts make it look.
 
This, there is no need to spend money on fancy drills working in 6061 or 7075 unless you have an excessive depth to diameter ratio. Unless of course you are trying to machine crappy Chinese 6061, then all bets are off.

P.S. Refrain from buzz words like billet. I can't believe it took till post #8 for a comment.

×3 on this, with an addendum. Don't spend money on fancy drills unless you have a high quantity of parts to do. It's not worth it. The benefit is small and it takes a lot of parts to add up to anything relevant in terms of the time spent. A plain bright drill or even black oxided drill will work just fine for one or two parts.

I've just been working on about 6 or 7 of these 80% lowers for a friend of a friend, using plain old black oxide drills. No problems whatsoever. Absolutely do use a reamer for things like the pin holes, and WD40 for cutting oil works great.
 
Gunsmithing, Aircraft piloting. Horse riding. Video game playing. Drinking, especially in nightclubs. Mainlining heroin. All activities in which I'm dead thankful I never took an interest.

I think Oscar Wilde said "I'll try anything once except folk dancing and incest."
 








 
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