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Old 02-05-2009, 02:33 PM   #1
Flattop
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Default Oversize barrel pin.

Anyone know where I can find an oversize barrel pin? The old pin is .277 I think I need to go with a .281 to set headspace.
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Old 02-05-2009, 10:51 PM   #2
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I think curtis @akbuilder and roger @ copes has em..
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Old 02-06-2009, 12:29 AM   #3
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One suggestion. You really need to ream the hole to get a good press fit. When you order your reamer (Enco probably cheapest - McMaster Carr biggest selection) just order some oil hardened tool steel (drill rod) and make it your self. Gives you lots of choices as far as how much larger you want/need to go. You can get the drill rod for a couple bucks for 3'.
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Old 02-06-2009, 12:43 AM   #4
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Default OT: DO you really need a reamer?

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Originally Posted by ETG
order your reamer (Enco probably cheapest - McMaster Carr biggest selection) just order some oil hardened tool steel (drill rod) and make it your self.
Since we are talking about an "interference fit", I generally make the hole about 0.002" less than the pin and press it in.

So does the hole really need to be reamed? I thought reaming was for precision work . . . I just dill mine.

Larry
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Old 02-06-2009, 12:53 AM   #5
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Reaming is always best if you want to make a round hole. Jobber drill bits do not make round holes "technically". Also, reamers drill the hole to whatever size specified. Drills do not.

Chuck up a .250 drill that actually measures .249 and you might get a hole that measures .250 or .254. (just throwing out examples)

Reamers are always best. Setting headspace should be precision work. Will drills work, absolutely!

-myers
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Old 02-06-2009, 12:55 AM   #6
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If you buy the same size bit as the pin you will not get a good press fit. If you have an undersized bit you may get away with it. Problem is, drills don't make round holes - but hey, it's an AK. Interference fit is diameter dependent - .002 is fine for barrel/trunnion but I normally go with .001 for 1/4' and under pins. Heard of a lot of guys buying the same size drill and pin (some have tried using the shank of the drill) and wondering why the pin falls through.
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Old 02-06-2009, 01:16 AM   #7
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Quote:
Originally Posted by FAL GRUNT
Chuck up a .250 drill that actually measures .249 and you might get a hole that measures .250 or .254. (just throwing out examples)


-myers
Exactly, you never know exactly what your going to get with a drill. You should always use a reamer for work like this.
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Old 02-06-2009, 01:35 AM   #8
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LOL - FAL GRUNT pushed post before I finished typing :-) For reference:

American National Standard Hardened Ground Machine Dowel Pins.—Hardened ground machine dowel pins are furnished in two diameter series: Standard Series having
basic diameters 0.0002 inch over the nominal diameter, intended for initial installations; and Oversize Series having basic diameters 0.001 inch over the nominal diameter, intended for replacement use.
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Old 02-06-2009, 11:13 AM   #9
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I use "drill blanks" in size J (0.277") for standard replacement. I typically use 19/64" (0.297" or +0.020") for my oversized ones. However, I once had a PSL kit were what looked like the factory pin was 0.310". So, YMMV.

I drill a couple thousandths under the pin size with a size M carbide drill bit. I realize that the hole produced by a drill bit is not nearly as precise as one made by a reamer. But I figured that while headspace is somewhat precision work, drilling a hole for a 0.002" press fit is decidedly not -- the hole just needs to secure the barrel pin. Just MHO and YMMV . . .

Larry
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