Can one recut a 6 x .75 nipple rifle to take 1/4 x 28 nipple? They seemed like they are close in size and I was wondering if there is enough metal to cut and convert the nipple size from metric to English. I have a GPR I'd like to convert to 1/4 x 28 nipple. Thanks for info.
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converting to 1/4 x 28
- Thread starter sprucefly
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6X.75 and 1/4X28 are very close in size but very different threads. If you run a 1/4X28 tap in, you will not have enough metal left of the threads to be safe to shoot, you may blow the nipple out. I would not take a chance on it. Why would you want to change, there are plenty of 6X.75 nipples on the market?
I must agree with DEADDOG.
Assuming you didn't crossthread the hole when you try to re-tap it, the 28 pitch of the .250-28 thread is different enough that the tap will be removing an increasing amount of existing thread material from the old threads with each revolution of the tap.
If you want a mathematical explaination, the .250- 28 pitch thread advances 1/28 or .0357 per revolution while the .75mm pitch advances .0298 inches. The difference is .0059 per rev. This difference means at the start of the second thread .006 of the old thread will have been removed. At the start of the third thread .012 will be removed. At the start of the fourth thread .018 will be removed. As the thread is only .029 thick at it thickest place, over 50% of the thread will be gone and your only three full threads (.107)down the hole with more to go. The small gain in diameter (.0115) is not enough to make up for this lost material. IMO this is not a good idea.
To the best of my knowledge, there are no nipples on the market (like Hot Shot etc) that you can get in .250-28 that you cannot also get in 6 X.75.
Assuming you didn't crossthread the hole when you try to re-tap it, the 28 pitch of the .250-28 thread is different enough that the tap will be removing an increasing amount of existing thread material from the old threads with each revolution of the tap.
If you want a mathematical explaination, the .250- 28 pitch thread advances 1/28 or .0357 per revolution while the .75mm pitch advances .0298 inches. The difference is .0059 per rev. This difference means at the start of the second thread .006 of the old thread will have been removed. At the start of the third thread .012 will be removed. At the start of the fourth thread .018 will be removed. As the thread is only .029 thick at it thickest place, over 50% of the thread will be gone and your only three full threads (.107)down the hole with more to go. The small gain in diameter (.0115) is not enough to make up for this lost material. IMO this is not a good idea.
To the best of my knowledge, there are no nipples on the market (like Hot Shot etc) that you can get in .250-28 that you cannot also get in 6 X.75.
Thanks for the info. You confirmed what I thought. I just like to reduce the number of different nipples I have to have. Most of my rifles are 1/4 x 28.
Too many nipples, huh? I used to know a gal in HS with three breasts, two in the normal place and one between her shoulder blades. Homely gal but everyone lined up to slow dance with her.
Seriously, iff'n you're serious about this, you could maybe buy the matching bolster (or make it) or sleeve the existing one. Probably have to anneal it first and would be best to have an extra. Big job for a lesser problem IMO but could be done.
Seriously, iff'n you're serious about this, you could maybe buy the matching bolster (or make it) or sleeve the existing one. Probably have to anneal it first and would be best to have an extra. Big job for a lesser problem IMO but could be done.
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