Starting work on Polymer Lowers

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Just got my new milling machine up and running and the first project was milling out the rear sight pins that hold the mount on my Mosin Nagant. Worked really well after melting the solder.

Anyway, getting back to the subject line, I have a few AR15 80% lowers some in polymer and some aluminum and was wondering what
types of end mills I should get to do the job correctly. I suspect maybe different ones for both materials. As a matter of fact I do not really know what speeds to use either. My experience with mills are about 15 years but just using what was set up to do little jobs at work so any input would be appreciated.

[Mayhem]

If I recall correctly, Highpower has a thread on here where he machined one of those aluminium receivers. That post and the pictures contained within may be of help.

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I'll see if I can find it, thanks

[Highpower]

I can't help with the polymer, but 400 SFM worked well for me on the aluminum. You'll need at least one "extra long" end mill to reach to the bottom of the fire control pocket.

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Thanks Highpower, I did get a set when I bought the polymer but they are not marked to what they are so that's why I asked about them. BTW, I went through your thread on the lower you did and all I can say is Awesome! I would love to do something like that but at my age and income, it wouldn't be worth getting all the tooling and equipment I would need so I have to stick with the easier stuff.

[ScrapMetal]

(10-06-2015, 11:57 AM)Highpower Wrote: I can't help with the polymer, but 400 SFM worked well for me on the aluminum. You'll need at least one "extra long" end mill to reach to the bottom of the fire control pocket.

Yep,  I like to use the extra long 7/16" endmill with a radius on the edge for that pocket.  Oh, and make sure it is a "center cut" type as well as that can come in real handy.

Here are a bunch of posts I brought over to my server that I had posted (on a different site) during my last AR build.  Hopefully it still makes sense - AR 80% lower build

When I get the time I'll have to fill in some gaps and make it more readable.

-Ron

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Thanks Scrapmetal, that looks like something I could follow or at least get some good ideas. I did already start a polymer 80% using my drill press and the jig that it came with but soon realized that I should hold off until my mill came in. I'll see if I can finish that one off before I start another one. I have a few polymer and aluminum ones to do.

[Highpower]

(10-07-2015, 10:07 PM)ScrapMetal Wrote: Here are a bunch of posts I brought over to my server that I had posted (on a different site) during my last AR build.  Hopefully it still makes sense - AR 80% lower build

Kudos Ron. That is a great write-up with some really nice pictures.

You made some good points with your thoughts on the jig sets. And I love the Monster Jaw fixture plates.

You've certainly got the building bug BAD!
Keep up the good work!

p.s.
Brownells has "cleaning nozzles" along with replacement spray nozzles for those pesky Aluma-Hyde rattle cans too. After they sit for so long they start to sputter and make a mess of things in my experience. I've had really good results using their baking lacquer with an airbrush though.

[ScrapMetal]

Thanks guys. I've got a few more lowers to do and will add more information to what I've already done. There has been a big delay in getting to the rest of these as my shop was broken in to a couple of months ago and they stole all my end mills, drills, welder, grinder, etc. etc. I'm just now getting tooled back up and in to the swing of things again. Added a folding security gate but still need to add some lights and video cameras. I really hate the low lifes that do that kind of thing.

Anyway, sorry for the short rant, after I finish these lowers I'm going to try and finish a couple of 1911 80% frames. I'll definitely try and document that as well.

-Ron