bits for aluminum 80%

[pakk]

I have a drill press and X Y 2 way.

I've had some practice with the eplowers that came out fine with carbide bits I have laying around from years past. I'm looking into jigs, but have not purchased one as of yet. I think I'm pretty much set on purchasing the TM jig.


My question is what bits are you guys using for aluminum lowers? I'm not sure if the ones I have will hold up.

[kcstott]

Four flute will work and is more common but if you had a choice two flute HSS center cutting end mills and Kerosine with a touch of high sulfur cutting oil mixed in.

[dchang0]

Like DRH above, I got the best results from two-flute center-cutting carbide 7/16" end mills. Went through a three-flute non-center-cutting HSS and a two-flute center-cutting HSS end mill, one per 80%. They dulled fairly quickly on forged aluminum and also vibrated more than the carbide one, leaving lightly-visible scalloping on the inside surfaces. HSS end mills seem to work fine on the softer billet aluminum.

We learned the hard way to do as much hogging-out as possible with drill bits, saving the end mills for just the two final finishing passes.

[kcstott]

We learned the hard way to do as much hogging-out as possible with drill bits, saving the end mills for just the two final finishing passes.

Yep we were told in trade school if you can drill it out or saw it off do it, save your mills for finish work

[ford63man]

I'm a fan of 3 flute center cutting end mills from msc direct.
the 3/8 bit I use is an accupro 65250060. machined 6 ar15 and 4 ar10s.
bits are still in great shape. and I use them to plunge to depth no drill bits.

[dchang0]

Yep we were told in trade school if you can drill it out or saw it off do it, save your mills for finish work

Wish I had gotten that far in metalworking. I stopped at the sheetmetal courses--never got to lathing/machining. D'oh!

Thankfully I've got a good teacher now…

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I'm a fan of 3 flute center cutting end mills from msc direct.
the 3/8 bit I use is an accupro 65250060. machined 6 ar15 and 4 ar10s.
bits are still in great shape. and I use them to plunge to depth no drill bits.

Re: three-flute end mills. One problem I ran into with these is that it's hard to get a good, accurate measurement of the diameter of the cutting flutes. That posed a problem later when I was cutting the rear takedown pin pocket and ended up not cutting enough--I wasn't able to fit an upper receiver into the lower! All my calculations had counted on the end mill to be wider than it apparently was.

We also found that plunge cutting was the only way to go for hogging out IF we used end mills (0.500"). Too much squeal/chatter otherwise. But big fat drill bits were the way to go in the end, just like the jig-makers' top plates are meant to be used with.

[ford63man]

if you dont know the diameter and are using 3 flute, take a pass on some scrap and stuff your caliper into the cut. if you are not using coated mills yes wd-40 is awsome. or you can rub a bit of nicks stick on the mill that is good stuff.

[kcstott]

You can measure a three flute endmill a few ways. If you have a set of calipers hold the end mill so the jaws are going down the side of the end mill you can pick up two points that way. Use a V mic, But not even I have one of those in the tool box. Just no need for it. Or you can use a V block and a depth mic then compare to pin gages. But the easiest way is to cut a piece of scrap and measure the grove.

Wd 40 works great as a cutting oil on aluminum

[Intimid8tor]

I definitely say drill everything you can first. It makes it easier, mill or not. WD-40 gallon jug and then a spray end on a long hose makes for a good setup for WD-40. I do like to use roughing end mills first to get close. They just cut through easier. Then I switch to a 2 flute and finish it off.

[yari]

I would say avoid carbide unless you have a good coolant system. They are expensive and extremely brittle. Hss and cobalt are much more forgiving. Drill then mill 3 flute will have less chatter. Use the 50/50 rule 50% the diameter depth and width of cut.