AR 80% lower finishing - Order of operations?

[ScrapMetal]

Finally received my spot drills and 5/32" reamers so I finished up my first lower yesterday. I had some "difficulties" setting up the lower in the vise and getting it properly situated. Putting a DTI on it after it was in the vise I was getting some odd variations front to back and top to bottom (it was on it's side so those terms are relative). After an hour or so of changing the way it was held, shimming, and other general messing around with it I decided that I didn't really know if the casting, especially after milling the pocket, was all that perfect in it's dimensions (and my "anal retentiveness" was getting in the way of actually making holes).

So I squared it up using the vise jaw as a reference and proceeded onward. I then spent an appreciable amount of time with a Blake co-ax indicator trying to find the center of a .251" hole. I don't have complete faith in the Blake and re-did it a number of times before I was satisfied with the results. First time I used it on a hole that small so I'm sure the more I use it the better it will go.

Being as things were not as "perfect" as I would like, and figuring this one would be a "test case" anyway, I ended up just spotting the near side, drilling straight through both sides, then followed that with the proper sized reamer. After I was finished I installed the trigger, hammer, and safety switch to test sizing and function. The holes came out within measurable tolerances and everything works as it should. The lower will now be dis-assembled until I receive my Brownell's order which contains a spray can of Aluma-Hyde II to coat the inner cavity and hopefully protect it from oxidation. I'd be curious to hear what others might be using for this.

Always waiting,

-Ron

 

[brav65]

Finally received my spot drills and 5/32" reamers so I finished up my first lower yesterday. I had some "difficulties" setting up the lower in the vise and getting it properly situated. Putting a DTI on it after it was in the vise I was getting some odd variations front to back and top to bottom (it was on it's side so those terms are relative). After an hour or so of changing the way it was held, shimming, and other general messing around with it I decided that I didn't really know if the casting, especially after milling the pocket, was all that perfect in it's dimensions (and my "anal retentiveness" was getting in the way of actually making holes).

So I squared it up using the vise jaw as a reference and proceeded onward. I then spent an appreciable amount of time with a Blake co-ax indicator trying to find the center of a .251" hole. I don't have complete faith in the Blake and re-did it a number of times before I was satisfied with the results. First time I used it on a hole that small so I'm sure the more I use it the better it will go.

Being as things were not as "perfect" as I would like, and figuring this one would be a "test case" anyway, I ended up just spotting the near side, drilling straight through both sides, then followed that with the proper sized reamer. After I was finished I installed the trigger, hammer, and safety switch to test sizing and function. The holes came out within measurable tolerances and everything works as it should. The lower will now be dis-assembled until I receive my Brownell's order which contains a spray can of Aluma-Hyde II to coat the inner cavity and hopefully protect it from oxidation. I'd be curious to hear what others might be using for this.

Always waiting,

-Ron

And they yelled... Pictures, pictures, pictures, pictures...

 

[ScrapMetal]

And they yelled... Pictures, pictures, pictures, pictures...

Yeah, I knew that was coming. I'll try and put some pics up tomorrow after I'm back out in the shop for a bit.

-Ron

 

[ScrapMetal]

Okay, you asked for pics, here are some pics... :biggrin:

The first couple of pics show how I set up the lower in my Kurt vise. I used a chunk of aluminum that was milled flat as a spacer/leveler to get the casting level side to side. The top of the casting was held against the fixed jaw in the Kurt which I had already squared up on the mill. I also placed a piece of cardboard to protect the trigger guard and magazine well edges.





No way would I try to mill anything like that but for making a few holes it was more than sufficient.

The next little procedure was to use my Blake co-ax indicator to establish the 0,0 mark for the DRO. Put the mill in back gear and reduced the speed to about 80 rpm.



Once that was established I simply lined things up for the hammer pin.



Installed a 1/8" spotting drill and marked the location.



Close-up of the "chips" from the spotting drill.



Followed that up by drilling a 1/8" hole all the way through both sides of the casting.



To finish out the first hole I used a 5/32" chucking reamer. Back gear and around 80 rpm again.



I'll spare you the procedure for the trigger pin as it was identical to the hammer pin.

Now it's on to the hole for the safety selector.



3/8" spotting drill doing it's thing.



In the next pic I used a 23/64" drill to make the hole through the casting. I could have maybe used a 3/8" but I don't trust the drills to be accurate and that would have left very little room for error. (Good shot of a long aluminum "rat tail". )



Like the previous holes I chucked up a reamer, 0.376" this time, and put the finishing cut on the hole. Here you can see where I had to slide the aluminum spacer out of the way. Once again, back gear and 80 rpm.



The "finished" lower.



A shot of the test fitting of both the hammer and trigger assemblies. I've since disassembled it as it's waiting for my Brownell's order and the Aluma-Hyde II paint. I did leave the magazine release and bolt release in as that shouldn't get in the way of painting the trigger/hammer cavity.



Now I'm just waiting for stuff to show up again. For this lower I'm waiting on a 7.62x39 upper from Northern Rifleman with a hand guard in Flat Dark Earth (the rest of the furniture will match). I'm planning on lowers for a .300 AAC Blackout, a 6.8mm Remington, a straight 5.56 x 54 NATO carbine w/piston, a 5.7 x 28mm FN (maybe, 'cause it looks kind of fun), and the more I look at/research it (thanks to Lucky 13 :biggrin: ) most likely a .223 Wylde.

Still just waiting,

-Ron

 

[Blackhawk]

Scrap,
hopefully this will make sense, if not ill post a video.
i indicate off the buffer then come forward 7.50 and zero. Then drop in a .250 drill blank, and since its at zero I indicate off the top of the blank and come down .225 and zero that axis. I also cut down the top of the ray v plates so I can indicate the sides closer to where I'm milling the fire control pocket.

love the idea of the vice jaw clamps, I have a lot of build parties and that would speed things up a bit

lanham

 

[ScrapMetal]

Blackhawk, I'll give that a try on the next lower(s) that I make. Thanks.

Tactical Machining was having a sale so I just had to pick up a few more. :biggrin: This time I picked up a few of the "raw" ones as I'd like to give Cerakote a try.

I did get a message from Brownell's that my Aluma-Hyde II is on the way. I'm a little concerned about applying the Aluma-Hyde as I've read that there could be issues with the spray nozzle clogging and that one should have extra nozzles on hand. Wish I knew that BEFORE placing the order. I'll certainly be posting to let you guys know how well it works out.

-Ron

 

[Blackhawk]

Scrapmetal,
thanks for the link, that's a smoking deal.
I have used their jig side plates at a build party and they have the dowels for the takedown pins which made setup a lot easier. Was going buy them till I saw the jaws you made now ill just copy your idea and add dowels.

lanham

 

[ScrapMetal]

Scrapmetal,
thanks for the link, that's a smoking deal.
I have used their jig side plates at a build party and they have the dowels for the takedown pins which made setup a lot easier. Was going buy them till I saw the jaws you made now ill just copy your idea and add dowels.

lanham

Good to hear. I hope you add your "jaws" build to this thread or your own when you get the chance.

Brownell's order showed up on my doorstep this afternoon so it looks like, with any luck, I'll be taping off and spraying some time tonight.

-Ron

 

[Lucky 13]

Blackhawk, I'll give that a try on the next lower(s) that I make. Thanks.

Tactical Machining was having a sale so I just had to pick up a few more. :biggrin: This time I picked up a few of the "raw" ones as I'd like to give Cerakote a try.

I did get a message from Brownell's that my Aluma-Hyde II is on the way. I'm a little concerned about applying the Aluma-Hyde as I've read that there could be issues with the spray nozzle clogging and that one should have extra nozzles on hand. Wish I knew that BEFORE placing the order. I'll certainly be posting to let you guys know how well it works out.

-Ron

I picked up 3 more 80% lowers and uppers from Tactical Machining black Friday sale. It's hard to beat $45 lowers and $29 uppers.

 

[catoctin]

Keying off your comment on oxidation, I did four DarkSoul Tactical lowers in early 2013 and my finishing process consisted of the following:
1. Mill the FCPs on raw lowers.
2. Make Adobe Illustrator templates for engaving. I used the Acad drawing found on line to determine the sizing and provide instruction to the engraver. It appear some and maybe all engraving machines like vector drawings provided by Illustrator. You just need to make sure the detail lines are compatible with the width of the engraving tooling.
3. Have the engraver do the engraving.
4. Have all four lowers glass bead blasted and Type III hard anodized.

By doing things in this order I didn't have to worry about oxidation. Prices vary on getting the last two operations done but doing them in batches helps bring the cost down.

Finally received my spot drills and 5/32" reamers so I finished up my first lower yesterday. I had some "difficulties" setting up the lower in the vise and getting it properly situated. Putting a DTI on it after it was in the vise I was getting some odd variations front to back and top to bottom (it was on it's side so those terms are relative). After an hour or so of changing the way it was held, shimming, and other general messing around with it I decided that I didn't really know if the casting, especially after milling the pocket, was all that perfect in it's dimensions (and my "anal retentiveness" was getting in the way of actually making holes).

So I squared it up using the vise jaw as a reference and proceeded onward. I then spent an appreciable amount of time with a Blake co-ax indicator trying to find the center of a .251" hole. I don't have complete faith in the Blake and re-did it a number of times before I was satisfied with the results. First time I used it on a hole that small so I'm sure the more I use it the better it will go.

Being as things were not as "perfect" as I would like, and figuring this one would be a "test case" anyway, I ended up just spotting the near side, drilling straight through both sides, then followed that with the proper sized reamer. After I was finished I installed the trigger, hammer, and safety switch to test sizing and function. The holes came out within measurable tolerances and everything works as it should. The lower will now be dis-assembled until I receive my Brownell's order which contains a spray can of Aluma-Hyde II to coat the inner cavity and hopefully protect it from oxidation. I'd be curious to hear what others might be using for this.

Always waiting,

-Ron