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  #1  
Old 06-29-2014, 8:47 AM
xaerorazor xaerorazor is offline
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Default AR-15 lower - 0% - build from billet

Good Day,
I may be new around here, but I'll be posting my progress on building an AR-15 lower from a piece of 7075-O Aluminum billet.

I have managed to get some 7075-O Billet on the cheap so i decided to build something from it. So I got myself some blueprints and am working on it. I'll add photos as I go.

My current progress:
Convert drawings into a Solidworks file.
2014-06-29
I needed to plan out how I will be milling it, so I have Solidworks available to me, which is great for planning on how to mill a piece of metal. I'm about 1/3 done with the model so far, I have one side left then to create the step by step sheets to build it.
2014-07-01
Model is done, about to make the step by step drawings....
2014-07-07
Project on hold due to billet issues...
2014-07-08
Project back on, going to do it on the -O after doing some research.
2014-07-20
I finally started machining, starting off on facing. Also did some measuring, and I have enough for a upper, also found out that a new instrument being built at work needs to be heat treated (also in 7075-o right now, metal was ordered wrong, but still needed to work on it), so I'll be slipping it in the shipment, their not charging me by the lb. So I'm happy to be getting a free up to -t6.

If anyone has any ideas or tips, please jot them down for me, and for others.

Last edited by xaerorazor; 07-23-2014 at 9:05 PM..
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  #2  
Old 06-29-2014, 8:58 AM
kcstott kcstott is offline
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Why don't you go over to CNCgunsmithing and download his solidworks file or the Iges?? Save you some work
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Old 06-29-2014, 9:11 AM
xfer42 xfer42 is offline
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I was going to try that, but I found that the 0% 7075 forging($20 @ rguns) was less $$$ than the huge block required. So it didn't make sense for my purpose.
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Old 06-29-2014, 4:34 PM
xaerorazor xaerorazor is offline
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Quote:
Originally Posted by kcstott View Post
Why don't you go over to CNCgunsmithing and download his solidworks file or the Iges?? Save you some work
I did get those files, and I'm using them to generate a new model. I kept having problems with feature ident on the models he has up, plus what features it did manage to ident were out of order and made no sense for milling by hand (i dont have a cnc/cam mill).
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Old 06-29-2014, 4:37 PM
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Originally Posted by xfer42 View Post
I was going to try that, but I found that the 0% 7075 forging($20 @ rguns) was less $$$ than the huge block required. So it didn't make sense for my purpose.
Picked up a scrap billet piece for $10, just happened to be the right size. Never know what you might find at a scrap sale.
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  #6  
Old 06-29-2014, 5:39 PM
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The 0% forgings do not let you build a custom billet with your own designs. You're limited to the standard milspec lookalike billet only.

e.g. integrated trigger guard for one.

I've milled out a lower from acrylic as practice, fun but time consuming for sure. I wouldn't even think about it without a CNC mill.
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  #7  
Old 06-29-2014, 9:32 PM
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Quote:
Originally Posted by Obstreperous View Post
I have not read of anyone finishing a % anything completely at home on a manual mill, accept for me I'm sure there are a few out there.
I thought about a billet but decided to use a forging and save any billet attempt for a AR10.

With all the AK parts kits out there and TM releasing there 1911 Frames, AR's have taken a back seat for now.

Good luck your project
I did a 10% three years ago only the mag well was broached. A month of sundays with building fixtures as I went. Fun though for sure and now there ain't a feature on the ar i can't get to with the mill. I can do the buffer retainer in my sleep

AR Build Not a tutorial or anything just documented my progress.
I would not do that again unless I had no other choice.
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Old 06-29-2014, 9:55 PM
xfer42 xfer42 is offline
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The last time I made one from a 0%, I think I got it down to about 16 hours. I could shave a lot time off. Ive cleared out 8 magwells with a CNC mill, and its the most un fun part because I have to babysit it all the way through. I use G83 operations and two different 1/8 in bits. That's one part that might actually be quicker with a manual mill (minus moving to the exact coordinates, and compensating for backlash).
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Old 06-29-2014, 11:04 PM
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You could hog 90% of the material out then broach the rest with a key way broach set.
I came up with this years ago

Machine two blocks of steel that will fit a finished mag well snug. Then machine the groves to support a 1/4" keyway broach for the corner radii and the other block for the tiny step and the mag catch slot.

You rough and finish the mag well except for the corners and the step. Drop in your die insert the broach, drench it in oil and shove it through. repeat three more times. then swap blocks and hit your mag catch slot.

Yes not the best way to do it but is beats trying to drill or using long thin endmills and if you design your blocks to use standard broaches tooling replacement is easy. You just need to grind a radius on the broach
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Old 06-30-2014, 12:14 AM
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If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.
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  #11  
Old 06-30-2014, 12:44 AM
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Quote:
Originally Posted by pacific_v View Post
If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.
Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.
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Old 06-30-2014, 11:26 AM
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Originally Posted by pacific_v View Post
If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.
CNCgunsmithing sells them and they are like $350 each

Quote:
Originally Posted by bigcalidave View Post
Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.

Yep lots of 3D surfacing and that takes a bunch of machine time.
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  #13  
Old 06-30-2014, 1:24 PM
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I'm pretty sure a forging is going to be stronger than a billet. Not that a billet is bad but why make something look like a forging that will take a lot of time, cost you more, and then be inferior?

I'll spend $1 for every 1% that is completed on a lower; that is a bargain.

ETA: Forgings are stronger because of how the grain boundaries follow the geometry of the part. When milling you have no choice but to cut across the grains thereby exposing more grain boundaries. In forgings the boundaries "flow" with the geometry. As all failures begin at grain boundaries it is desirable to have fewer of them intersecting the surface of your part.


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Last edited by Lostsheep; 06-30-2014 at 1:34 PM..
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  #14  
Old 06-30-2014, 1:36 PM
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make the billet lower thicker.
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Old 06-30-2014, 10:08 PM
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Quote:
Originally Posted by bigcalidave View Post
Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.
I've seen one done before and it looked beautifull. Also with a billet lower everything would be a lot more true and without any variance of being off by a thou or two in certain areas, or also wouldn't have little nicks, dings, etc etc.
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Old 06-30-2014, 10:09 PM
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Originally Posted by kcstott View Post
CNCgunsmithing sells them and they are like $350 each




Yep lots of 3D surfacing and that takes a bunch of machine time.

Please link me as the only lower I'm aware of from Justin that goes for $350 is his 416 cloned lowers.
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Old 06-30-2014, 10:25 PM
bigcalidave bigcalidave is offline
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Quote:
Originally Posted by pacific_v View Post
I've seen one done before and it looked beautifull. Also with a billet lower everything would be a lot more true and without any variance of being off by a thou or two in certain areas, or also wouldn't have little nicks, dings, etc etc.
Most of that is not true. Not sure why you think a thou or two in certain areas would even matter, what "a lot more true" means, and the nicks and dings come on everything. Usually with billet receivers there are machining marks and other marks. When you want to make a firearm look perfect, it takes metal finishing skills. It just doesn't make any sense to take a billet and cut it to look like a forging.
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Old 07-01-2014, 4:56 AM
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Why are you using -O condition material?
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Old 07-01-2014, 5:21 AM
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Originally Posted by pacific_v View Post
Please link me as the only lower I'm aware of from Justin that goes for $350 is his 416 cloned lowers.
And you understand that the difference between a HK416 and a AR15 lower is the markings for the most part correct??
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Old 07-01-2014, 5:55 AM
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Quote:
Originally Posted by kcstott View Post
And you understand that the difference between a HK416 and a AR15 lower is the markings for the most part correct??
NO, the biggest difference is the magwell. Heck if Justin did do a Billet lower after a forged one with the correct fencing and everything else I'd be all over that thing but I do know that the machine time involved to do so would ballpark the price quite high up there.
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  #21  
Old 07-01-2014, 6:36 PM
xaerorazor xaerorazor is offline
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Quote:
Originally Posted by Obstreperous View Post
Good catch O material condition is to soft for a lower IMHO and not as easy to machine.
I was able to get the billet on the cheap. I can still get it tempered to -t6 seeing as it's untempered right now, plus I have a 2hp mill at my disposal.
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Old 07-02-2014, 6:09 AM
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Quote:
Originally Posted by pacific_v View Post
NO, the biggest difference is the magwell. Heck if Justin did do a Billet lower after a forged one with the correct fencing and everything else I'd be all over that thing but I do know that the machine time involved to do so would ballpark the price quite high up there.
Well yeah an ever so slight angle change. I'm still not understanding WHY you want a lower made from billet. It makes zero sense to me especially since you want a mil spec copy that makes even less sense.

What is wrong with a forging that you have to have a billet copy??
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Old 07-02-2014, 11:37 PM
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If I were going to machine up a lower from billet from scratch, I would make up something no one else has. Something awesome

For mil-spec, do a forged 80%. Why waste the effort?
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Old 07-07-2014, 11:41 AM
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Looks like I wasted some cash... I can't get my billet heat treated locally (no-one is willing to do it for the cash I have). guess I'll have to see if I can find another piece...
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Old 07-07-2014, 11:52 AM
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Quote:
Originally Posted by xaerorazor View Post
I was able to get the billet on the cheap. I can still get it tempered to -t6 seeing as it's untempered right now, plus I have a 2hp mill at my disposal.
Quote:
Originally Posted by xaerorazor View Post
Looks like I wasted some cash... I can't get my billet heat treated locally (no-one is willing to do it for the cash I have). guess I'll have to see if I can find another piece...
How cheap was this billet? You could get a piece of bar stock sufficient to make a lower for less than $20.

Dude, just buy a forging....
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Old 07-07-2014, 12:00 PM
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Quote:
Originally Posted by xaerorazor View Post
Looks like I wasted some cash... I can't get my billet heat treated locally (no-one is willing to do it for the cash I have). guess I'll have to see if I can find another piece...
Toss it on a charcoal grill with the lid on overnight
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Old 07-07-2014, 2:44 PM
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Quote:
Originally Posted by xaerorazor View Post
Looks like I wasted some cash... I can't get my billet heat treated locally (no-one is willing to do it for the cash I have). guess I'll have to see if I can find another piece...
and that because it will take about three days from start to finish.

a good long soak at 900˚f+ then a quench then a temper to around 350˚F for 24 hours then a slow cool and back in your hands.
the cost is in the energy used and the attention needed to do it correctly.

http://www2.mae.ufl.edu/designlab/On...rgy%20Info.pdf

Last edited by kcstott; 07-07-2014 at 2:47 PM..
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Old 07-07-2014, 5:27 PM
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Quote:
Originally Posted by Lostsheep View Post
How cheap was this billet? You could get a piece of bar stock sufficient to make a lower for less than $20.

Dude, just buy a forging....
I got it for $10
Quote:
Originally Posted by kcstott View Post
and that because it will take about three days from start to finish.

a good long soak at 900˚f+ then a quench then a temper to around 350˚F for 24 hours then a slow cool and back in your hands.
the cost is in the energy used and the attention needed to do it correctly.

http://www2.mae.ufl.edu/designlab/On...rgy%20Info.pdf
That is what I learned today...
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Old 07-07-2014, 5:37 PM
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Quote:
Originally Posted by xaerorazor View Post
I can't get my billet heat treated locally (no-one is willing to do it for the cash I have).
Get more cash.
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Old 07-07-2014, 5:53 PM
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Quote:
Originally Posted by xaerorazor View Post
I got it for $10

That is what I learned today...
think about this a 0 material condition chunk of 7075 is 45,000PSI tensile
a piece of 6061 T6 is the same tensile and they make billet lowers out of that all day long. I know it ain't the same but it no worse then what people are selling for full retail.

Thing is if you are local I know a guy at a aircraft shop that might be able to sneak in a chunk of material if I greased his palm a bit, they run heat treat of material daily

Last edited by kcstott; 07-07-2014 at 5:55 PM..
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Old 07-08-2014, 10:57 AM
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Quote:
Originally Posted by kcstott View Post
think about this a 0 material condition chunk of 7075 is 45,000PSI tensile
a piece of 6061 T6 is the same tensile and they make billet lowers out of that all day long. I know it ain't the same but it no worse then what people are selling for full retail.

Thing is if you are local I know a guy at a aircraft shop that might be able to sneak in a chunk of material if I greased his palm a bit, they run heat treat of material daily
Thank you for the offer, but I will try it out on the -O material. I ran some numbers and feel that it's still doable.
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Old 07-08-2014, 11:29 AM
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Quote:
Originally Posted by kcstott View Post
think about this a 0 material condition chunk of 7075 is 45,000PSI tensile
a piece of 6061 T6 is the same tensile and they make billet lowers out of that all day long. I know it ain't the same but it no worse then what people are selling for full retail.

Thing is if you are local I know a guy at a aircraft shop that might be able to sneak in a chunk of material if I greased his palm a bit, they run heat treat of material daily
3 things:

1. Yield is what you should be concerned with, not ultimate.
2. Check your numbers.
3. As it is aluminum we are talking about and I assume everyone wants infinite life; multiply your yield ultimate stress by .4 to get your maximum allowable stress (this will get you in the ballpark).



7075-0 yields at 14K not 40K




...

Last edited by Lostsheep; 07-08-2014 at 12:50 PM..
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Old 07-08-2014, 6:18 PM
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Quote:
Originally Posted by Lostsheep View Post
3 things:

1. Yield is what you should be concerned with, not ultimate.
2. Check your numbers.
3. As it is aluminum we are talking about and I assume everyone wants infinite life; multiply your yield ultimate stress by .4 to get your maximum allowable stress (this will get you in the ballpark).



7075-0 yields at 14K not 40K




...

Good point
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Old 07-08-2014, 7:37 PM
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Seeing as this is a first time test, i'm going to try it on the 7075-O. I'm looking at it this way, if I make a mistake, I'm not going to fret about it. If it works out, hey, all the better. I just found out the collets(L20) I have access to are the wrong size for the large mill (R8) I have access to. This happens to be a mishap left over from the consolidation of two workshops into one before I started working. (I've been using side screw tool holders)
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Old 07-08-2014, 8:32 PM
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Quote:
Originally Posted by xaerorazor View Post
Seeing as this is a first time test, i'm going to try it on the 7075-O. I'm looking at it this way, if I make a mistake, I'm not going to fret about it. If it works out, hey, all the better. I just found out the collets(L20) I have access to are the wrong size for the large mill (R8) I have access to. This happens to be a mishap left over from the consolidation of two workshops into one before I started working. (I've been using side screw tool holders)
You mean Weldon holders.

Get on ebay and look up discount machine. R8 collets are like $6 each and are pretty darn good too.
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  #36  
Old 07-08-2014, 9:31 PM
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Have you tried probing a lower?
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