Cross threaded nipple after cleaning..........Help!

[slowtrack50cal]

Well, the subject says it all.  I cross threaded the nipple on a Lyman Plains Pistol.  Wrecked both the nipple and the breech plug.  I could buy another, but wanted to check here for any other options.  The thread pitch is 6 x .75

[Roger Fisher]

Far from being a machinist so you need input from others here!!

I do believe that Brownells or Track of the Wolf sells oversized taps and nipples that should fix her!!

Don't be tempted to force fit the current crossthreaded beastie   Even in the low
charged pistole!!  I have seen at least 2 nipples launch themselves out of their seats due to crossthreading no injury fortunately!! 

[Dphariss]

I don't know how to figure metric threads but I suspect that you can likely retap to 1/4 x 28.
If you do this get a H1 tap from MSC or some other machine shop supplier. This will produce the tightest fit in the threads. If its too tight order a H2 and run it in. The tighter tolerance increases strength and reduces fouling entering the threads if the nipple does not seat properly. I use a piloted counter bore to cut a nipple seat in the breech so the nipple seats tight against its shoulder.
Re-tap, install a new steel nipple and proof with a double charge and 2 balls. It is best if percussions are proved by percussion cap rather than powder train as a flint is done.

IF the threads do not look suitable then go with the OS tap and nipple combination.
It is possible it cross threaded due to "tolerance" between the nipple and the threaded hole.
The tolerance for bolts and nuts is enough to assure everything will got together and when the "slop" stacks up toward the loose end things can get pretty sloppy.
See http://www.newmantools.com/taps/taptech.htm#gh
For Info on tap tolerance and thread fits.
You will likely need both a Plug and a Bottoming tap. Use a good tapping fluid. The stuff I use contains moly and taps seldom bind up even when cutting stainless.
If the breech is anything but dead soft this might be a lifesaver.

Dan

[rick landes]

How badly did you xthread the nipple? Most times these can be turned in a majority of the way by finger tightening. IF you just buggered the top thread or two you may just have to cleanup the threads and insert a new nipple.

Sometimes on small fine threads I will slowly turn the nipple or bolt backward until I feel the thread drop into the tapped slot; then I slowly tighten the part in.

Make sure you think thru how this happened so not to do it again or at minimum when you do it again you know why it happened. It is just another learning experience . I am thoroughly convinced a professional is not one who does not make errors, only one who knows how to fix them when they happen.

Good Luck

[Dphariss]

Having blown a nipple out once upon a time I take thread fits pretty seriously.
If it had a couple of bad threads I would tend to retap.

Dan

[Dphariss]

Having blown a nipple out once upon a time I take thread fits pretty seriously.
If it had a couple of bad threads I would tend to retap.

Dan

[BobT]

If I recall correctly the major diameter of a 6mm thread is .236 and the clearance drill for a 1/4-28 is .207. I don't know if you would get a full clean-up or sufficient thread contact by re-threading. I would err on the  side of caution and go with a new drum. I blew out a nipple on a 12 bore one time and it's not an experience I care to repeat.