Milling a cast AR-15 lower...

[indoorsoccerfrea]

I just ordered a solid-cast AR-15 lower for $35 after shipping, and also have downloaded some CAD drawings of all the various dimensions/specifications of a finished receiver. I don't know much about CAD, but from the little research I have done, it seems like there should be a scale-reference somewhere on the blueprint, which does not seem to be there...

Anyone know what they are doing?

Anyone done this before? Any tips?

Any help is much appreciated!

-David

 

[rockydog]

you might check out CNC CNCGUNSMITHING - www.cncguns.com - AR15 80% Tooling / Drill Jig

 

[turnandshoot4]

Great link!

 

[indoorsoccerfrea]

I'm not using a CNC machine, I'm doing this with a drill press and other assorted power tools. That link does have all sorts of things that will be helpful, so I guess my main question is this:

How do I scale the blueprints correctly?

 

[ddenny5]

I know how to use many CAD software and I am also a CNC Programmer. Look at the title block of the drawing (if there is one) and the scale should be listed there. The title block should be in the lower right hand corner. If you want me to see the blueprint let me know.

 

[indoorsoccerfrea]

ddenny5, is there a way to get the blueprint to you? it won't let me pm you the url.

http://www.biggerhammer.net/ar15/cad/ar15_receiver.pdf

is where it is at

 

[rockydog]

What dimensions are you needing? unlike the AKs I've built, the ARs are really too percision for scaleing. CAD drawings are drawn 1 to 1 (unlike old school board drawings) and very little scaling is done anymore. If you need a certain dimension you should be able to find it and do a layout from there. Good luck

 

[sloughfoot]

I'm not using a CNC machine, I'm doing this with a drill press and other assorted power tools. That link does have all sorts of things that will be helpful, so I guess my main question is this:

How do I scale the blueprints correctly?

Partner, you just made my list of guys to never buy an AR from....

 

[indoorsoccerfrea]

I want to do something similar to what this guy did...

Weaponeer Forums

print a template that is to scale, then past and drill. Obviously I am going to try it on wood for starters just to get the process down before I start cutting on my aluminum one.

 

[indoorsoccerfrea]

Partner, you just made my list of guys to never buy an AR from....

Haha, well, if I can get this to work, I certainly won't be selling it!

 

[ddenny5]

I have saved the blueprint. That is a good blueprint with some good GD&T. That website listed is a very good website. They have the hole drilling jigs if you need to drill the holes to finish the lower. Let me know what it is exactly you need from this print.

 

[lawrra]

the cad drawings should be 1:1 in the drawing. If you print them, be sure to select print 1:1

 

[gunselman]

I have been looking into doing something like this for quite some time. I have a background in 3 and 5 axis machining and many years of CAD/CAM experience. If i was to tackle a project like this with a drill press i would stay away from the 0% forgings and look to an 80% forging. DIY GUNS and Tactical Machining has them. They take out most of the areas where people mess up (mag well and buffer tube). $80 from tactical machining is a pretty good deal if you are going to be doing a few. I would be interested in splitting the 5 pack from Tactical machining if you would be interested in something like that.

If you are interested in a billet 80% lower try Yellow Logic . They have a really nice looking product but it is more expensive.

Here is a link to the work that it takes to finish a 0% raw forging. Login

If you have any questions let me know i have been researching this for quite some time.

 

[indoorsoccerfrea]

They're already 1:1 in the drawing? That makes things considerably easier, haha. The reason I want to make it from a 0% is because I have a foundry, and I can make more 0% forgings easily. I want to see if I can do it this way, so that I will have essentially my own personal supply of lowers for the price of one 0% lower.

Ddenny, what I wanted from the blueprint was to be able to print it in scale 1:1. I have no experience with CAD and all that jazz, so I didn't know how to tell if it was 1:1 or if I had to scale it myself before printing.

I have another though as well, I have a lot of 2" thick plexiglass, would that be a durable enough material if cut to milspec sizes? What do you guys think? If not, I could just do what the guy in the posted thread did with his Pine Abortion.

 

[sp3worker]

I would have to agree with gunselman, I don't believe a 0% forging is going to turn out well being made on a drill press, if at all. I don't think you could do the internal machining very easily on a drill press, broaching the mag well would be fun too. You said you have a foundry and wanted to make more 0% lowers, will they be cast or forged? And so you know, neither the wood or plexiglass will cut anything like the aluminum. I'd look for a block of aluminum to practice on. Keep us updated, I'd like to see how this one turns out.

 

[indoorsoccerfrea]

I would have to agree with gunselman, I don't believe a 0% forging is going to turn out well being made on a drill press, if at all.

I'm wondering how it will turn out also, but for $35 I think it is worth it to have a possible supply for personal lowers. Plus, I think it will be a fun experience.

You said you have a foundry and wanted to make more 0% lowers, will they be cast or forged?

They will be cast. I suppose I may be able to cast 80% or maybe even finished lowers as well, but for obvious reasons I want to make a few 0% castings from the one I have ordered before I start cutting on it.

And so you know, neither the wood or plexiglass will cut anything like the aluminum. I'd look for a block of aluminum to practice on.

Agreed, but the sheer awesome-ness of having a clear lower makes me want to try it...plus it will help me understand more about the process of setting up and milling.

Keep us updated, I'd like to see how this one turns out.

I certainly will, but it will be a while...Milling the lower won't start until spring break and over the summer as well, since making a lower while living on campus probably would not be a wise idea...

 

[PatMcGroyne]

"I certainly won't be selling it!"

Hah! Of THIS I'm quite sure! BTW, it's highly illegal (interpret: "10 / 10") to sell or transfer any unserialized and registered "gun" (your lower, all by itself IS a "gun) to any other unrelated person without BATFU approval, all the paperwork, and provenance! Good luck in Da 'hood!!! Pat

 

[indoorsoccerfrea]

Hah! Of THIS I'm quite sure! BTW, it's highly illegal (interpret: "10 / 10") to sell or transfer any unserialized and registered "gun" (your lower, all by itself IS a "gun) to any other unrelated person without BATFU approval, all the paperwork, and provenance! Good luck in Da 'hood!!! Pat

Just so you know, there is no gun registration in Indiana. I am also legally allowed to sell a gun I make, as long as there are numbers or some type of serial number on it. I am not allowed to sell for profit or make it a business, but I am allowed to sell it (meaning one or so).

 

[sp3worker]

They will be cast. I suppose I may be able to cast 80% or maybe even finished lowers as well, but for obvious reasons I want to make a few 0% castings from the one I have ordered before I start cutting on it.

I don't think that casting an 80% lower is possible. Casting gernerally doesn't result in the high tolerences required to make an 80% lower. 0% could be done though.

Agreed, but the sheer awesome-ness of having a clear lower makes me want to try it...plus it will help me understand more about the process of setting up and milling.

A clear lower would be neat. Not sure if plexiglass has the strength needed for a lower though. I guess if nothing else it would be a cool novelty and you could see how the gun operates. I wouldn't want to be the first to try firing it.

Hah! Of THIS I'm quite sure! BTW, it's highly illegal (interpret: "10 / 10") to sell or transfer any unserialized and registered "gun" (your lower, all by itself IS a "gun) to any other unrelated person without BATFU approval, all the paperwork, and provenance! Good luck in Da 'hood!!! Pat

I'm sure they wouldn't frown on it any more than your supposed "Iraq bring back Russian AK".

 

[indoorsoccerfrea]

I don't think that casting an 80% lower is possible. Casting gernerally doesn't result in the high tolerences required to make an 80% lower. 0% could be done though.

What if I cast something that only had the mag well and trigger assembly slot cut out? None of the pin holes or buffer tube connection would be drilled yet.

A clear lower would be neat. Not sure if plexiglass has the strength needed for a lower though. I guess if nothing else it would be a cool novelty and you could see how the gun operates. I wouldn't want to be the first to try firing it.

Oh, I would remote fire it...at first, haha. Maybe if I did what this guy did, such as leaving the plexiglass thicker so it wasn't mil-spec, it would retain enough strength...

Weaponeer Forums

edit to add: Can anyone access the above link? It isn't working for me now...