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Page AR-15 » Build It Yourself
AR Sponsor: bravocompany
Posted: 2/12/2017 12:20:09 PM EDT
I milled my first 80% lower yesterday and everything went smooth except I milled the fire control pocket too deep. It's about 1/16-3/32" thick on the bottom of the pocket (I can see the thickness when looking at the trigger hole). When I look at other factory lowers that I own it appears that are about 1/8-5/32" think on the bottom. (pardon the rough estimates ;) My question is, did I ruin this lower or will it function? Is there a way to fix it if necessary?
Link Posted: 2/12/2017 12:21:30 PM EDT
[#1]
if you can't see daylight you're good.
Link Posted: 2/12/2017 12:31:26 PM EDT
[#2]
It will function fine, put it together and perform the function test, if it passes, go shoot it.
Link Posted: 2/12/2017 1:44:03 PM EDT
[#3]
Next time go slow, measure, cut, measure cut.............and don't go deep.
Link Posted: 2/12/2017 1:50:18 PM EDT
[#4]
I personally haven't use it, but some say you can us JB Weld to fix minor problems.  Try it if it fails the test and let us know how it came out.

Bill
Link Posted: 2/12/2017 3:12:48 PM EDT
[#5]
There shouldn't be a load on that section of the lower. Think of the lower as a automobile frame. There is a small amount of torque exerted but nothing tremendous. If you are worried, you could put a layer of epoxy or a liquid metal alloy which is made by Permatex and JB. But think about it, lower are made with 3D printers or polymers. I wouldn't loose sleep over it.
Link Posted: 2/12/2017 5:18:59 PM EDT
[#6]
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Quoted:
It will function fine, put it together and perform the function test, if it passes, go shoot it.
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this
Link Posted: 2/12/2017 5:23:32 PM EDT
[#7]
It will work. I've got one I knocked a hole in the bottom of. I had to use a drop in trigger because their wasn't anything for the trigger springs to compress against
Link Posted: 2/12/2017 8:25:57 PM EDT
[#8]
Thanks everyone! I feel a bit better . I ordered a LPK today and will have it installed next weekend. I'll post a reply on how she functions. Appreciate ya'll!!
Link Posted: 2/12/2017 9:22:12 PM EDT
[#9]
Don't use JB Weld, use Alumaweld. Put a piece of tape covering the trigger slot and pack it in the bottom 1/4" thick, then re-machine out the bottom and trigger slot. I messed up a couple of lowers and made the bottom so thin, it was flexing. The other, the mill bit walked out and cut a hole in the bottom from front to back. I fixed both with Alumaweld and it sets up rock solid and bonds with the lower extremely well.
Link Posted: 2/12/2017 9:24:12 PM EDT
[#10]
It will work fine.  The only purpose of the material around the trigger slot is to prevent dirt and debris from getting into the trigger group.  You should be able to mill all the material through the bottom of this area and still have no problems.
Link Posted: 2/13/2017 12:54:42 AM EDT
[#11]
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Quoted:
It will work fine.  The only purpose of the material around the trigger slot is to prevent dirt and debris from getting into the trigger group.  You should be able to mill all the material through the bottom of this area and still have no problems.
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Not true. There has to be enough material left on the bottom shelf for the trigger spring legs to rest on.
Link Posted: 2/13/2017 5:58:07 AM EDT
[#12]
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Quoted:


Not true. There has to be enough material left on the bottom shelf for the trigger spring legs to rest on.
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Good point.  Still not much material needed to accomplish this, though.  And installing a drop-in trigger group makes this a null point.
Link Posted: 2/13/2017 7:51:30 AM EDT
[#13]
On my first 80% i drilled one hole too deep and did as one other person suggested. I filled the bottom with JB Weld and milled it again. Worked great and is still holding up after a 1000+ rounds. I am sure Alumaweld will work as good or better but always seem to have used JBWeld for stuff like this.
Link Posted: 2/13/2017 8:44:20 AM EDT
[#14]
Quoted:
I milled my first 80% lower yesterday and everything went smooth except I milled the fire control pocket too deep. It's about 1/16-3/32" thick on the bottom of the pocket (I can see the thickness when looking at the trigger hole). When I look at other factory lowers that I own it appears that are about 1/8-5/32" think on the bottom. (pardon the rough estimates ;) My question is, did I ruin this lower or will it function? Is there a way to fix it if necessary?
View Quote


No. As long as their is metal. A little JB weld on the bottom. Smooth it out. Wait 24 hours and you can re mill if desired. Have done this before.
Link Posted: 2/13/2017 11:43:18 AM EDT
[#15]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
On my first 80% i drilled one hole too deep and did as one other person suggested. I filled the bottom with JB Weld and milled it again. Worked great and is still holding up after a 1000+ rounds. I am sure Alumaweld will work as good or better but always seem to have used JBWeld for stuff like this.
View Quote


The reason I use Alumaweld is it is an aluminum putty, it bonds with aluminum better, can be molded by hand and stays put. JB Weld is pretty runny and can get away from you if you're not careful. It bonds pretty well with all metals but I believe in using like materials for repairs.
Link Posted: 2/14/2017 8:18:37 AM EDT
[#16]
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Quoted:


. JB Weld is pretty runny .
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Huh? I must be using something else.
Link Posted: 2/14/2017 10:58:43 AM EDT
[#17]
If you have 60 thou left just go with it.  I'm embarrassed to say that after doing a handful of them, and on my fourth on tyhat particular day, I cranked 13 times on the knee of the ole Bridgeport instead of 12 and completely milled thru the bottom of the trigger pocket (well not quite, there was metal there but you could see thru it).  I don't remember where I got the receiver, but it must not have been 7075 because I was able to machine a plate and TIG it into the receiver and remill it.  It was for a retro so it actually looked like I had salvaged a demilled receiver.  Increased authenticity I'm telling myself.
Link Posted: 2/14/2017 12:32:16 PM EDT
[#18]
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Quoted:


Huh? I must be using something else.
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Quoted:
Quoted:


. JB Weld is pretty runny .


Huh? I must be using something else.

By runny, I mean it's not like the Alumaweld putty. I've used JB Weld to repair an 80% lower and had to tape over the holes with duct tape to hold it in place. It works great, just not my preferred method. I think Alumaweld is easier to work with.

ETA:

I have wanted to try and melt some aluminum cans and re-pour the damaged section if it happens again. I wonder how well that would work.
Link Posted: 2/17/2017 3:21:48 PM EDT
[#19]
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Quoted:

I have wanted to try and melt some aluminum cans and re-pour the damaged section if it happens again. I wonder how well that would work.
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Probably not very well, the melting point of Al and the boiling point of Al are not very far apart. It takes very little effort to go from melting the Al to metal to then boil it to vapor
Link Posted: 2/17/2017 8:34:12 PM EDT
[#20]
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Quoted:


Probably not very well, the melting point of Al and the boiling point of Al are not very far apart. It takes very little effort to go from melting the Al to metal to then boil it to vapor
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Quoted:
<strong>Quoted:</strong>

I have wanted to try and melt some aluminum cans and re-pour the damaged section if it happens again. I wonder how well that would work.


Probably not very well, the melting point of Al and the boiling point of Al are not very far apart. It takes very little effort to go from melting the Al to metal to then boil it to vapor


good point.
Link Posted: 3/3/2017 9:46:27 PM EDT
[#21]


Got the LPK installed and the verdict is....trigger works just fine,  didn't even add any JB Weld or anything of the sort. Guess I was all worried for nothing. Thanks to all for their advice!
Link Posted: 3/4/2017 10:20:24 PM EDT
[#22]
Sweet...glad it worked out.  Like it was mentioned, it's just there to keep the majority of debris out.  Function should be okay.
Link Posted: 3/8/2017 9:37:24 AM EDT
[#23]
Can a off center cut bad trigger slot cut in a 80 % lower be tigged up and recut correctlly?
Link Posted: 3/9/2017 12:14:25 PM EDT
[#24]
The trigger is held in place by the hammer and trigger pin.  These are independent of the bottom of the receiver so having the fcp milled too deep won't affect it.

If it was too shallow on the other hand, you wouldn't be able to move the trigger or drop the hammer.
Link Posted: 3/11/2017 12:49:56 AM EDT
[#25]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
if you can't see daylight you're good.
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This
Link Posted: 3/12/2017 12:57:33 PM EDT
[#26]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


The reason I use Alumaweld is it is an aluminum putty, it bonds with aluminum better, can be molded by hand and stays put. JB Weld is pretty runny and can get away from you if you're not careful. It bonds pretty well with all metals but I believe in using like materials for repairs.
View Quote


Are you talking about alumbond?  Alumaweld searches get me fishing boats and Alumiweld gets me welding rods, not putty.
http://www.alumaweldboats.com/
https://www.alumiweld.com/

alumbond on the other hand is a two part epoxy putty.
https://www.cambridgelsat.com/bookstore/hy-poxy-h-450-alumbond-65-oz-aluminum-putty-repair-kit/B001RMITIA/
Page AR-15 » Build It Yourself
AR Sponsor: bravocompany
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