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rdesign
01-22-2009, 08:59 PM
I have started building a couple AR's for a fun winter project. There are plenty of great places to buy forgings, 10% complete or 80% complete lowers but I decided to start with blocks of 7075 T6. I paid $80 for all 4! I was pretty happy.

The rougher is a 3 flute 3/4" aluminum rougher I run at 3000 RPM (600 SFPM) and that thing has cut A LOT of aluminum, the second pic is in action at speed! There was a pretty good blizzard of chips and coolant going on but the picture makes it look tame. For finishing I used a .125" ball end mill at 6000 RPM (wish I had more) and a .005" stepover.

I love how this 7075 T6 machines. It is noticeably harder than 6061 but less sticky when you push it.

Not time effective, not cost effective but fun. The cncguns.com guy is my inspiration on this one.

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSCN2536.jpg

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSCN2543.jpg

http://i201.photobucket.com/albums/aa315/rdesign_photos/ARBLOCKS.jpg

alanganes
01-22-2009, 09:26 PM
Wow! Nice work. I almost want a CNC now...

meho
01-22-2009, 09:49 PM
Outstanding!

Check this out. http://ray-vin.com/frtech.htm

Ken_Shea
01-23-2009, 12:03 AM
Nice work rdesign !
I do not see the many required holes drilled, is there a reason you did not do those when machining?

Where did you get your 7075 ? that seems like a VERY good price.

I have machined 7075-T6 and agree, it sure does machines nice.

6000rpm is better then 4000 but 10-12K would sure have to make a big difference in machining time, my limit is now 6K, that was bumped from the normal 4K, even the 2K a big difference, hard to imagine what another 4-6K would make.

Looking forward to your progress.

Are you getting nervous on AR-15 type gun ownership yet ?



Ken

andy_b
01-23-2009, 05:18 PM
rdesign,

they look good so far! i'm also wondering why you didn't do the rest of the holes when machining the basic receiver. i have an 80% right in front of me and just need the time to work on it. what type of setup are you planning on using to drill the hole for the bolt retaining latch rollpin? i think most of the other holes should be pretty straight forward.

what are you planning with regards to hard anodizing the receiver once it's finished? there are a few people who frequent this board and do anodizing as a business, but i'm not sure they would want to handle non-serialized receivers. heck, i am not even sure if they legally can.

andy b.

BillC
01-23-2009, 09:13 PM
Wow those are sweet!! can or are you selling any of those??.

rdesign
01-23-2009, 10:02 PM
I'm working on holes tonight. I didn't drill them because I wanted to do all the roughing and surfacing in one program without doing manual tool changes and I need more tool holders. In retrospect I should have picked a drill and at least piloted them. I was maybe a little anxious to get cutting and that will cost me some time now.

For the latch pin hole I have a long aircraft drill with which I can reach it while the part is standing vertically, buffer hole up. The drill bit will clear the side but it is a long reach. Basically I'll do it just like the cncguns.com guy. I will likely do that one on the bridgeport do to the fact that I don't think I have enough Z travel on the CNC mill.

I plan to anodize myself. I have an account with a local metal finishing company, but I plan to go on my own for this one. I should call and ask them if they would/could do it, you have me curious.

I have a 2 gallon setup here that I haven't tried yet. I think I have everything I will need. I am just planning to use a manual battery charger though. I have a variable autotransformer I could try to use on the AC side so I can reduce AC voltage in to the charger - will that work to ramp up and vary the DC output or will the charger just try to make 14 VDC no matter what the input is? A quick test should answer that. Then I will try anodizing a few peices of scrap and see what happens I guess. It will be a somewhat nervous day when I put my lowers in there!

I'm still trying to decide what to engrave on them after anodizing. I was thinking "Molon Lave" but I have seen that done. Any ideas?

I will not be selling lowers. I would have to be licenced from the ATF to do that. These are purely for personal use!

Ken_Shea
01-23-2009, 10:16 PM
I'm still trying to decide what to engrave on them after anodizing. I was thinking "Molon Lave"

Greek for what seems to mean "Come and take them" :D

rdesign
01-23-2009, 11:07 PM
I'm still trying to decide what to engrave on them after anodizing. I was thinking "Molon Lave"

Greek for what seems to mean "Come and take them" :D

I figure many would not get it, I kind of like that.

rdesign
01-23-2009, 11:50 PM
I made these two blocks tonight for holding the lower in the vise now that I have no good way to grip it anymore. I used a different setup block for machining the second side. That block is not going to not work going forward.

http://i201.photobucket.com/albums/aa315/rdesign_photos/FIX1.jpg

http://i201.photobucket.com/albums/aa315/rdesign_photos/FIX2.jpg

Ken_Shea
01-23-2009, 11:59 PM
Nice work on the fixture, machining is easy, it is the set up and fixturing that is difficult. Some I know just love that aspect, I for one do not, wish I did though.

.

rdesign
01-24-2009, 10:29 PM
Three drilled one in progress.

I just did the right hand side holes, the setup for the left hand side will be the same. I am drilling somewhat manually. I have all the holes listed as a coordinate in MDI followed my an M30, I just run the command line that corresponds to the hole I want for the drill I have in the collet chuck. Progress will slow due to the demands of the next week but I will pick this back up in Feb.

I want to get this drilling done because I'm excited to do the pocketing. Then I can test fit an upper!

http://i201.photobucket.com/albums/aa315/rdesign_photos/DRILLING2.jpg
http://i201.photobucket.com/albums/aa315/rdesign_photos/DRILLING1.jpg

Ken_Shea
01-24-2009, 10:57 PM
That's kind of a bummer having to essentially quit until February, that is not a long way off but once you get on a roll picking back up is not always so productive.

They are looking real good !

Did you drill/ream or drill only ?

rdesign
01-24-2009, 11:21 PM
I machined the selector hole. Other holes were just drilled. I don't own many reams anyway.

It is coming out pretty good so far. Takedown pin holes are supposed to be .251 +/- .001", my 1/4" drill was coming out about .2504"-.2505". Trigger pins are supposed to be .156+/- .0015, my holes are .1560-.1565". The surface looks nice in there. Another reason I like this material!

Anodize will add a couple tenths and I will be pretty close to nominal.

rdesign
02-05-2009, 04:41 PM
Ramping back up on this, I did a little pocketing last night. I am planning to machine and thread mill the buffer hole tonight.

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02490Small.jpg

531blackbanshee
02-05-2009, 06:57 PM
great project!thanks for posting the pictures,keep us posted.

leon holmes

rdesign
02-06-2009, 12:40 AM
Well, this was the first one tonight to test the program and there was a mistake, can you spot it?

The .5" hole is supposed to be .2" deep + the tip and I only drilled .2" including the tip. If I had not taken it out of the vise so quick it would have been easier to touch up.

This was the first time I had ever threadmilled anything! The surface is as smooth as it looks.

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02501.jpg

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02496.jpg

rdesign
02-06-2009, 12:44 AM
I am so slow. A friend of mine said that some shops have these things down to 30 minute cycle times from taking a forging to a fully machined lower.

Can anyone confirm or disprove that?

38_Cal
02-06-2009, 05:37 PM
And how many hundreds of thousands of dollars worth of machines and fixtures do they have to be able to do that? It's called economy of scale...

David
Montezuma, IA

rdesign
02-08-2009, 05:11 PM
David, of course, very true.

Made some more progress. Assembled the uppers Friday night. I am waiting for some longer reach tooling to finish the pocketing. Hopefully the tooling will show up Tuesday, I might be able to shoot a couple rounds through these things this week pre-anodize!

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02540.jpg
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02541.jpg

tdmidget
02-08-2009, 11:41 PM
Of course they can do them in 30 min or less. Because they :
Follow the Golden Rule of " do it in one set up". You will NEVER get those holes as close as you could have in the original set up. They do that, and probably rotate it in a 4th axis to do the other sides. Probably at 20,000 rpm. And probably run by a guy who is half asleep because it is so boring.

howiesatwork
02-09-2009, 06:35 AM
I'm doing a couple from forgings, but will be nowhere as nice, or done as quickly as yours.
How are you going to finish into the corners of the mag pocket?
A full-sized broach would be nice, but $$$

rdesign
02-09-2009, 09:22 AM
On the mag well, I am cleaning up the profile with a 1/8" end mill. The aluminum GI mag that I checked slides in just fine. Do the sharp corners in the side relief channels really need to be reproduced if the magazines are fitting fine without them? I will probably have to do a little filing if there is a match line where the machining from each side meets. So far I have not touched these lowers with any abrasives, the pictures posted are as machined only. I know they aren't perfect but they are pretty good.

On the hole locations, they might not be as close as they would have been in the original setup -but in my own defense- I located the parts within about .0005" before spotting and drilling the holes. The mil-spec tolerances on this gun are pretty large. So far, what I have measured is very close to nominal.

rdesign
02-09-2009, 09:48 AM
Of course they can do them in 30 min or less. Because they :
Follow the Golden Rule of " do it in one set up". You will NEVER get those holes as close as you could have in the original set up. They do that, and probably rotate it in a 4th axis to do the other sides. Probably at 20,000 rpm. And probably run by a guy who is half asleep because it is so boring.

I don't see any way you can get a forging through in one setup, but I haven't seen a lot. You have to approach the part from all 6 sides plus two holes off axis (grip and buffer detent). If you have the parts on a 4th axis you could do 4 sides in one setup, you would still have to machine from each end for the front takedown detent, the buffer drill/tap, rear takedown detent, and the two off axis holes. It would be cool to see how it is done! Especially the broaching.

The main reason I did machining and drilling in different setups is that I don't have enough tooling to have done it without having to change out tools and do a LOT of tool length offset work between parts. The way I did it I could do a group of operation to all 4 parts with a group of tools loaded. I typically located the parts back in the vise within about .0005" (the selector hole was my 0,0) and I trusted that the vise jaws remained parallel to the x. I consider myself an advanced beginner at best so I do aknowledge I may fail to see my error. Given my limitations and the accuracy requirements of this gun I am comfortable so far.

PackardV8
02-09-2009, 11:38 AM
I consider myself an advanced beginner at best

"Advanced beginner" - not hardly! We hereby promote you to Intermediate. ;)

thnx, jack vines

rdesign
02-12-2009, 03:13 AM
I finished everything I could reach from the top, I just have the mag well bottom to pocket/surface and the front takedown lugs to separate!
I can almost smell the powder!

http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02552.jpg
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02553.jpg
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02554.jpg

Ken_Shea
02-12-2009, 09:34 AM
I know you have had to work very hard on those, all that work has not been for nothing, they look perfect.

madman
02-13-2009, 09:22 PM
Reminds me of when i used to work in the Aerospace Shop. I have a lot of respect for wormanship of this Calibre Nice work. Mike

knedvecki
02-15-2009, 10:05 AM
Just for reference. When I worked for a place in Colorado, we did the upper receiver forgings in three minutes and three positions on the table, using a rotary axis on a HAAS VF-0. Second op was to broach the rear sight rectangle. It is always best to give yourself some tooling holes for fixturing / alignment to make sure everything is right with the world. And yes, of course I did aircraft.

rdesign
02-16-2009, 12:44 AM
I am basically done machining. I need a #42 long reach drill to do the mag catch and they are done. I will do some engraving post-anodize. I assembled a gun today and I have test fit uppers to all the lowers. So far so good!

There are probably a dozen things I can think of to make this go much faster. I have never attempted anything this complex before. I pretty much took it in managable hobby-size chunks, not the best approach for optimizing anything. As a self taught machinist I'm sure I missed many things that could have made these easier/better.

pcarpenter
02-16-2009, 06:13 PM
I own one Rock River Arms rifle and just bought a second lower from a guy who owns a gun shop on the side but works at RRA full time. They are about 1.5 hours away. I will try to remember to ask him about what their cycle times are on a new forging when I go to pick up the lower.

I am green with envy, however....I would really love to have one of those "billet" lowers. For an "advanced ameture", you have done really nice work. I would have been sweating bullets doing the thread milling (for example) as a first-time thing on a part that had turned out so nicely and was literally one operation away from being turned into scrap:rolleyes:

I am quite impressed and am glad you showed us your work!

Paul

rdesign
02-17-2009, 12:19 AM
Test fired today.

Two are glass bead blasted, the other two need a little sanding in the mag well first.
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02574s.jpg
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02577s.jpg

One of the AR's...
http://i201.photobucket.com/albums/aa315/rdesign_photos/DSC02579s.jpg

gzig5
02-17-2009, 11:10 AM
rdesign,
There are a couple folks on homesgunsmith.com that are making recievers from forgings or blocks. You will have to join to see the pics, but there are a lot of great ideas and some scary ones there. One guy talked about 32 minutes to do everything except the magwell which he is now EDM'ing in a seperate op.

Hey Paul, tell your friend to quit screwing around and get back to work at RRA and get the backlog whittled down. I just got my lower and am waiting on my WOA upper to arrive.

Greg

rdesign
02-17-2009, 04:17 PM
rdesign,
There are a couple folks on homesgunsmith.com that are making recievers from forgings or blocks. You will have to join to see the pics, but there are a lot of great ideas and some scary ones there. One guy talked about 32 minutes to do everything except the magwell which he is now EDM'ing in a seperate op.

Hey Paul, tell your friend to quit screwing around and get back to work at RRA and get the backlog whittled down. I just got my lower and am waiting on my WOA upper to arrive.

Greg

I just looked at that site. Interesting. After EDM'ing it sounds like he is around 1 hour of machine time per part. He is playing a totally different ballgame than me and my hobby project. Just fixturing for this scale operation would be significant.

Probably 75-80% of the machining time was bringing the block material into a shape that would equal a forging. I plan post a picture or two once these things are anodized and engraved, then this project is done.

gzig5
02-18-2009, 11:19 AM
Are you doing your own anodizing or farming it out and if so where and what do you expect to pay? I'm going to order one or two forgings and one of my concerns is finishing. I'd like to do it myself, but I'm not ready to commit. If I farm it out and the anodizing costs $50+, I might as well buy a stripped lower.

38_Cal
02-18-2009, 11:41 AM
As an alternative to anodizing, if you are working with an alloy that doesn't need the hardness factor from it, is to go with one of the spray-on/bake-on finishes, like GunKote or similar.

David
Montezuma, IA

rdesign
02-18-2009, 11:27 PM
I have a small (2 gallon) anodizing setup. I plan on doing these myself, the spirit of this project has been to do it myself. I have had quite a few parts anodized professionally in the past. I imagine the 4 would cost me $125 which is the minimum setup charge with the anodizer I typically use. Parts of similar size have ran me as little as $5 each in large quantities, I can't imagine these running more than $20 each if I had a dozen or two to do. It depends on how well it fits on their racks and surface area among other things.

How thick would that spray on coating be? I would have some fit problems if it is more than a few tenths unless I masked a lot of areas.