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Discussion Starter · #1 ·
HELP,
my spot welded sar gas pistons are wearing out near the bolt carrier. i removed the piston, but the slag buggered up the threads.now my new piston want screw in. i need a tap but don't what size.
jeff
 

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Try a 1/2 x20 if you cant find the proper metric tap.I couldnt find one so I went that route and it works its close enough.
 

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I just went through this when I made the pistons on my lathe. the thread is metric 12mm x 1.25. I am sorry to say the standard thread did not wrok for me at all. but I did find the metric tap and did in a local hardware store of cheap money. it is a hanson brand die U.S.A. made like $4 each . not too bad.
 

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4 bucks? wow I can never find anything I need that cheap around here. I always end up ordering shit from 10 states away and it seems to take forever and a day to get it.
 

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droog said:
4 bucks? wow I can never find anything I need that cheap around here. I always end up ordering shit from 10 states away and it seems to take forever and a day to get it.
That's what happens to me all the time...LOL
 

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the best i can offer is to buy one for you and mail it to you for actual postage. i was planning on going to buy another one for myself anyway. let me know !!
 

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meyerse said:
Did they by any chance have a 1/2-28? Why is this die so expensive????
vector has that die with a 1" od for $8.90 and a 1.5" od for a few bucks more!!
 

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I sent an email about a 14 x 1.00 left tap so I will know soon enough and let you guys know.
 

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In the early 1900's the Soicety of Automotive Engineers(SAE) set standards for bolt diameters and thread pitchs used in the mfg. of automobiles.The standard thread sizes for 1/2" bolts was National Corse(NC) at 13 theads per inch and National Fine(NF) at 20 threads per inch. The SAE standards were pretty much adopted by all industries in the USA by the 1930's.
So 1/2-28 having 28 threads per inch is a odd thread size as just about the only thing it is used on is the barrels of AR-15/M-16 rifles. As with anything less demand = higher price.
 
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