Re-barreled a Century built 74. Need help..
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    Re-barreled a Century built 74. Need help..

    I had to re-rivet the front trunnion and throw away what ever sorry excuse of a barrel they had on there to begin with. The barrel pin was already .315” and after drilling and reaming the new barrel today the new pin I have slips right through the hole. Am I screwed? I’m not even sure where to find over-oversized pins. The .315” pin I have is like throwing a hotdog down a hallway. I used an 8mm reamer...

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    ….."oversize" pin (?).
    …….cheaper than another barrel.

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    I'm not a builder/machinist by trade. But I drive past the Holiday Inn Express almost every day.
    1mm=.040"x8=.320"
    Press fit is -.001-2" or .01-.02mm
    So you're going to need a .322"/8.02mm pin.
    Correct?
    Anybody?
    Troll Out
    Gman likes this.
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    if you have a buddy w/ a lathe you can have them make you a pin a thou over what you reamed it.
    scottyb likes this.
    not taking new work

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    Just a thought but depending on how loose the barrel pin is you could try peening it. Like knurl it but use a hammer and punch.

    After all, it is a century 74.

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    Quote Originally Posted by 22many View Post
    Just a thought but depending on how loose the barrel pin is you could try peening it. Like knurl it but use a hammer and punch.

    After all, it is a century 74.
    In that case,Century would have used a rock and nail.

    Sent from my E6833 using Tapatalk

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    You can try Pin Gauges from McMaster-Carr. They offer a large selection of sizes in both US inch and Metric.
    BR7.62, scottyb, Mekanak47 and 1 others like this.
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    Quote Originally Posted by BR7.62 View Post
    if you have a buddy w/ a lathe you can have them make you a pin a thou over what you reamed it.
    Is there any special material I should use? I’m assuming something already heat treated?

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    i cant imagine it would really need it but i use 4130 and harden it.
    iraqvet has a great idea though and easier,
    individual pin gauges are like 4$
    not taking new work

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    So I found one of my old M14 flash hider alignment tools that was rusty and served no purpose since I only used it once. The fat end of the shaft measured .330” so I cut it and chucked it in my drill press. After about and hour with a file and jewelers files I got it pretty concentric and down to .317”. I cut it in half and pressed it in with some loctite 620. It didnt take a ton of effort on the 12ton to press in. I actually drove it a little far on one side and was able to recenter it with just a heavy duty punch and hammer. Do you guys think its tight enough? Am I over thinking it? I thought about peening both ends of the pin but maybe I’m being over cautious..

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    Quote Originally Posted by twobyfour View Post
    I actually drove it a little far on one side and was able to recenter it with just a heavy duty punch and hammer. Do you guys think its tight enough?
    If you can recenter it with a hammer, it's not tight enough.
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    Well crap

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    Quote Originally Posted by twobyfour View Post
    Well crap
    Press the pin out, knurl it as 22many says, press back in. Use powdered iron inside the hole to ensure a firm lock up.
    "Men who are not free... always idealize their bondage." - Boris Pasternak

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    Quote Originally Posted by crslasher View Post
    I'm not a builder/machinist by trade. But I drive past the Holiday Inn Express almost every day.
    1mm=.040"x8=.320"
    Press fit is -.001-2" or .01-.02mm
    So you're going to need a .322"/8.02mm pin.
    Correct?
    Anybody?
    Troll Out
    8mm = .315" (.31496") But drilling to same diameter as pin can be risky. Runout, slightly undersized pin or poor drilling technique can lead to a poor fitting pin.

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    I made another pin from the same material as the first. It fit extremely tight and required the helper bar on my press. I’m surprised it didnt explode going in. Also, for everyones awareness, you cannot knurl or peen an existing AK barrel pin, at least not one from AK-builder. Those things are extremely hard. I broke an automatic center punch, chisel head, and busted a small corner on my vice trying to make some sort of ripple. All it did was discolor it slightly.
    Richard W. and 22many like this.

 

 
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