nipple threads

[buggybuilder]

I have a T/C Hawken and the nipple seems to not screw in easily. It would be possible to screw in all the way, but I don't want to cross thread it and ruin the plug. I want to run a tap in and "freshen" the threads. Is the correct tap size a 1/4 x 28?
thanks

Bob

 

[necchi]

Is the correct tap size a 1/4 x 28?
thanks Bob

Yes.

I recently,(2 years ago) picked up a second hand T/C barrel that someone "oversized", and I couldn't replace the nip with a standard 1/4x28. If this is the case for you it might be wise to measure the existing nip to be sure it's the correct size. Oversize begins with .005 over and works up in .005 increments.
.255-.260-.265 >> .285x28

p.s. I sent it back to T/C,,they replaced the breech under the "warrenty"

 

[Zonie]

If screwing the nipple in with just finger pressure is the problem there are several different things that could be wrong.

1. The nipple is a replacement nipple with the wrong threads on it.
It could be a M6 X 1 nipple made for a CVA.
It could be an oversize .255-28 made for damaged threads.

If your sure the nipple is the original one you should try replacing it with a 1/4-28 thread nipple. There are several very good aftermarket brands available.

2. The existing threads in the bolster have a buildup of hard fouling in them.

Wetting the threads with water and running the nipple in and out several times using finger pressure should remove this fouling.

If the nipple can be started and run in to the hole for at least 2 full turns with finger pressure it is properly aligned and engaged.
If this is true, using a standard nipple wrench to tighten it further should not cause any damage if only a moderate amount of pressure is needed.
Under no circumstances should you need to use a lot of torque to get the nipple to screw down until its flange touches the barrel.

3. Someone has cross-threaded the nipple and forced it into the bolster.

A close examination of the threads damaged this way will show galled or severely damaged threads.
Rethreading these threads with an oversize nipple or a tap will NOT repair the damage.
A barrel with a bolster with damaged threads from crossthreading should be sent back to the factory to be professionally fixed.

As for running a tap into a threaded hole, it is very easy to start one of these mis-aligned with the existing threads.
Because the tap is made to cut material it can easily start cutting new threads in this mis-aligned condition and doing this will totally destroy the good threads that were there.

Unless you have experience in restarting a tap into a threaded hole, I do not recommend that re-threading with a tap should be done.