Will my AVID CNC do this

Hello Friends !

I have a AVID PRO4896 with NEMA 34, 4HP Spindle.

I am a gun range shooter and my tool of choice is the AR15. I would like to own a Skeletonized AR15 Receiver set but the prices for a matching lower and upper are pretty high. Given my machine specs above and looking at the two pictures i’ve attached I would like to know if my cnc could handle milling the recessed areas’ in one of the pictures and the all the way through on the second picture?

Any opinion’s, suggestions, tips, or tricks are very welcome

Your machine is fully capable of something like that. The challenge will be the work holding. I would suggest learning to cut 6061/7075 aluminum first before tackling this project. It is much cheaper to scrap normal stock than AR parts.

Luckily, of all the things in the world, I would expect there to be lots of examples available of workholding for AR receivers.

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I’ve done a bunch of these. The best advice I would give is to mill a nest designed to support the whole receiver perpendicular to the spindle. I made mine out of 7075 machinable jaws in Chick Workholding double station vise. But I have those resources from work and because I wanted to keep these for the occasional project (engraving, etc.). MDF would work fine for the occasional project. If you have fusion360, and a solid model of the receiver, simply do a MODIFY>COMBINE (selecting your fixture material as the TAGET BODY and the receiver as the TOOLl)>CUT. Then, turn off the Ar15 receiver view and you should have a nested profile of the receiver. Clean up the design by removing or opening up all of the details to make it less complicated. Before you cut the nest, pin its location so you can re-locate it on other ocassionas and perhaps assign it an unused G5xPx offset to make it easy. If you don’t have fusion, PM me and I can help you out.

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I believe you read my mind. Over the past week I have been trying to figure out a work holding solution. I was thinking two pieces of MDF glued together that I would set the receiver down into. I have about 60 lowers so It wouldn’t hurt my feelings if I messed up 1……maybe….I would like to get it right the first time haha. My bits from tools today.com for this project will be here tomorrow morning. I would like to make this a weekend project

I will PM you.

Thanks so much !!

Do you use fusion? I have something I can share by sending a file tomorrow if you’d like. Basically you could mill right out of mdf…and the geometry confirmed for a production cast MIL-SPEC lower (like Cerro forge or Anderson’s). There is a difference in the castings from various forges on non-tolerance dimensions, most on the outside, which is where you’ll nest off of, so the nest I made accounted for these variance. It locates off the top deck and the front takedown pin.

Let me know if you like it. It will save you time at the very least.


Yes I have Fusion360. I’m far from an expert but I might be able to wing it. All of my forget lowers are Anderson. I have so many of those because I can get them for 30.00 bucks. I’ll PM you my info.

Thank you for your help !!!

Do you support it from the inside of the receiver as well or have you found that its rigid enough leaving it hollow?

@pketcham when do you think you will be able to send me what I need? Bits arrived a few hours ago. Anxious to cut my first skeletonized Lower.

Your milling almost exclusively THROUGH the wall, so all of your milling force is radial (Side-load) rather than axial (pushing down against the par). No internal clamping needed.