Advice on fixing an elongated hole.
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    Default Advice on fixing an elongated hole.

    Hi ! I have an rifle receiver made of 7075 aluminum, and the trigger pin has worn an elongated, eccentric hole in the receiver's right side. These pins are usually 0.154, with a maximum hole diameter of 0.157. My idea was to find the proper position of this feature on the blueprint, put a center drill there on the milling machine, center-drill until the eccentricity is gone, drill and/or ream slightly larger, then make a pin that is a couple thousandths smaller than that new hole on the far right, and 0.155 for the rest of the pin (the hole through the trigger is also 0.157). I had been thinking of just installing a bushing, but could find none that had a 0.154-0.156 hole, with a depth less than or equal to the wall thickness. Another idea was to turn all but about 1/8" of a 0.170 pin down to 0.155, but this also became complicated.
    How does this idea sound? Any suggestions or better ideas? What should I use to make this? I know McMaster-Carr has lots of different materials, as does some of the online metal shops. Thanks!

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    Get a new one...why take a chance with a trigger.

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    I would not trust a rifle receiver in which the trigger pin has worn one hole into an elongated shape. Workmanship or material deficiency? Why would you trust the thing to fire live ammunition, whether you "fix" the worn hole or not? Time to give up the ghost.

    For those who do not understand the ghost reference, here is an explanation. What Are Ghost Guns and Why Are They So Dangerous? | HowStuffWorks

    Larry

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    Very good point. Maybe it's not even 7075. Oh well; to the band saw.

    The article's understanding of the law is incorrect. As long as you're able to legally possess, and you never sell it, you're in compliance. As far as carrying, I'm not as certain. I don't carry, so I've never looked into that. It doesn't seem like it would be a good idea, for a number of reasons.

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    Tig and rebore? As someone that lives in one of the less free states I would not destroy it.

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    Quote Originally Posted by jodifu6274 View Post
    Hi ! I have an rifle receiver made of 7075 aluminum, and the trigger pin has worn an elongated, eccentric hole in the receiver's right side...
    Quote Originally Posted by gregoryd View Post
    Tig and rebore? As someone that lives in one of the less free states I would not destroy it.
    TIG is not a good idea for 7075.

    Aluminum Workshop: Why isn’t 7075 weldable?

    Larry

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    Quote Originally Posted by jodifu6274 View Post
    Hi ! I have an rifle receiver made of 7075 aluminum, and the trigger pin has worn an elongated, eccentric hole in the receiver's right side. These pins are usually 0.154, with a maximum hole diameter of 0.157. My idea was to find the proper position of this feature on the blueprint, put a center drill there on the milling machine, center-drill until the eccentricity is gone, drill and/or ream slightly larger, then make a pin that is a couple thousandths smaller than that new hole on the far right, and 0.155 for the rest of the pin (the hole through the trigger is also 0.157). I had been thinking of just installing a bushing, but could find none that had a 0.154-0.156 hole, with a depth less than or equal to the wall thickness. Another idea was to turn all but about 1/8" of a 0.170 pin down to 0.155, but this also became complicated.
    How does this idea sound? Any suggestions or better ideas? What should I use to make this? I know McMaster-Carr has lots of different materials, as does some of the online metal shops. Thanks!
    I'm going to assume this is an ar that needed to be finished, also going to assume you did the finishing. Nothing wrong with that great and more power to you.
    Having said that if what I assumed is true. you shouldnt be attempting to fix it let someone who knows what there doing fix it. yes it can be fixed and theres a million ways to fix it correctly, but you have to have the knowledge and experience to do so.

    Delw

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    [get a new rec. ] ya right . ok so being it aluminum is it a 22 long rifle? is it a bolt gun or semi auto ?
    so if there room bush the org. hole with a loctited steel sleeve and cut out the sleeve were the trigger goes. also is this something that was new at one time and has worn or is it something that someone is making up ? if it was new at one time and one side were the trigger pin goes is still good then put a pin in that hole that is snug and set the rec. up in a mill so that the pin is parallel and centered to the spindle and remove the pin and ream a7/32 hole and make a bushing and install it and if there's room go with a 1/4 od bushing after all its not going to the moon its not like steve jobs was the last one that touched it and it would be bad mojo to even think about even looking at it stop over thinking it and fix the dam thing after all its just a machine

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    Quote Originally Posted by 1yesca View Post
    [get a new rec. ] ya right . ok so being it aluminum is it a 22 long rifle? is it a bolt gun or semi auto ?
    so if there room bush the org. hole with a loctited steel sleeve and cut out the sleeve were the trigger goes. also is this something that was new at one time and has worn or is it something that someone is making up ? if it was new at one time and one side were the trigger pin goes is still good then put a pin in that hole that is snug and set the rec. up in a mill so that the pin is parallel and centered to the spindle and remove the pin and ream a7/32 hole and make a bushing and install it and if there's room go with a 1/4 od bushing after all its not going to the moon its not like steve jobs was the last one that touched it and it would be bad mojo to even think about even looking at it stop over thinking it and fix the dam thing after all its just a machine
    Some things you just don't half ass my man.

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    I’m going to assume you’ve got an M16, or at least an sbr, other wise you just replace it. M16’s getting rewelded is pretty common.
    Attached Thumbnails Attached Thumbnails d5e5b235-be6b-4a1a-bc33-bcf702823601.jpg  

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    Quote Originally Posted by plastikdreams View Post
    Some things you just don't half ass my man.
    ya and there not a ting about that repair that would be half ass if its not an ar and there's room to support a bushing

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    Quote Originally Posted by Nmbmxer View Post
    I’m going to assume you’ve got an M16, or at least an sbr, other wise you just replace it. M16’s getting rewelded is pretty common.
    and i 2nd that but the thing is these clowns that post this stuff never tell you what there working on it always[ i got this ] ok you got this what ? ya if that's what he has then my above approach is not the way to do it in this case as there's no room for a bushing . but if its not an ar and there is 1/4" or more per side then the bushing would work

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    Quote Originally Posted by L Vanice View Post
    TIG is not a good idea for 7075.

    Aluminum Workshop: Why isn’t 7075 weldable?

    Larry
    They have made progress in that area. Here is an article talking about welding 7075:

    Nanoparticle-enabled phase control for arc welding of unweldable aluminum alloy 7075 | Nature Communications

    I think I have seen the talked-about filler rods now for sale.

    Filler rods:
    Home - MetaLi (metaliusa.com)
    Last edited by David_M; 06-21-2021 at 04:16 PM. Reason: Added source

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    Assuming the hole was originally round, if it wore into an elongated shape It was likely an issue where the pin rotated in the receiver rather than the trigger rotating around the pin.

    Done properly, I don't see any issue with installing a bushing. When I see the comments about it being unsafe I don't see that as an issue unless the geometry is wrong and affects sear engagement.

    The repair would need to be done properly and I agree that if the OP is not sure they can do it correctly they should take it to a pro.

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    Quote Originally Posted by 1yesca View Post
    and i 2nd that but the thing is these clowns that post this stuff...
    Nice. Maybe you should brush up on the spelling, grammar, and syntax of your native language before you call people clowns.
    I omitted that, because there are people in this country who get their panties in a wad and suffer vaginal irritation when they see the letters "AR" put together, so unlike you, I thought, "why be needlessly confrontational". I guess I failed to consider that some people are just looking for it anyway.

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    Drill out the damaged hole for a bushing retained with loctite

    Do what needs to be done to get the new hole in the right location and the correct size.

    A milling machine will come into play one way or the other.

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    Good grief, so much nonsense. This is a common issue and they sell anti-rotation pin sets to prevent such wear. Re-cut the hole properly located and oversized, make bushings to match, Locktite them in place and re-assemble with commercially available anti-rotation pin set and be done with it. For those not up to speed on the Armalite Rifle platform, the aluminum receiver doesn't carry much load at all, the bolt locks into a steel barrel extension, this is why even plastic receivers work fine.

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    Quote Originally Posted by wp6529 View Post
    Good grief, so much nonsense. This is a common issue and they sell anti-rotation pin sets to prevent such wear. Re-cut the hole properly located and oversized, make bushings to match, Locktite them in place and re-assemble with commercially available anti-rotation pin set and be done with it. For those not up to speed on the Armalite Rifle platform, the aluminum receiver doesn't carry much load at all, the bolt locks into a steel barrel extension, this is why even plastic receivers work fine.
    If a bushing like this is good enough for an F-18, it'll work just fine, on about anything else!

    And I have made and installed an awful pile of little wee bushings in various places on those!

    Plastic, yup! Ikea Cutting boards, For The Win! LOL!

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    My brother has run a FAA certified welding and fabrication shop for 43 years. He welds 7075 all the time. All I know is he says it is not easy but can be done with good results.

    For those that say scrap the receiver, you are wrong. All guns that are used regularly wear parts out. Guns are not made to last forever. If they were you could not afford to buy one. I have a Beretta pistol where the aluminum frame cracked. It was welded up and machined back to new in the mill. About a thousand rounds later, all is still OK.

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    Quote Originally Posted by jodifu6274 View Post
    Nice. Maybe you should brush up on the spelling, grammar, and syntax of your native language before you call people clowns.
    I omitted that, because there are people in this country who get their panties in a wad and suffer vaginal irritation when they see the letters "AR" put together, so unlike you, I thought, "why be needlessly confrontational". I guess I failed to consider that some people are just looking for it anyway.
    never going to happen i get a kick out of you spelling / grammar Nazis if that's your only argument then you have none so get on with life


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