Cross thread concern

[Cory Joe Stewart]

Folks,
I was fitting a breech plug and on one of the test fits I discovered very fine ribbons of steel that resembled finger nail clippings.  Maybe three of them.  I immediately feared that I had cross threaded the breech but the plug threads and the breach itself appear fine and fell nice and sharp to the touch.  Any idea what this was???

Cory Joe Stewart

[oldtravler61]

   Cory no expert but it might be from when the breech was tapped an the threads we're not cleaned out properly. Then when you inserted the breech plug the burrs we're removed. Or vice versa. Curious what the expert's have to say. Just my 2 cents. Oldtravler

[tiswell]

 To cross thread where fingernail sized clippings are produced would take some force. Were you cranking on it or just snugging it up. Are you certain the threads (both pitch or teeth per inch and diameter) are compatible? If you were just snugging it up and the threads are compatible I would say that it is possible that the chips were hiding in the barrel threads.

[Cory Joe Stewart]

Fingernail size is a bad analogy, depends on when  you cut your nails.  They were half moon shape.  I was just snugging it.  I was not using a lot of force at all.

[EC121]

Could be tapping debris or a wire edge that broke off when being snugged.  Cross threading to the point of generating debris while bottoming out would take a good wrench to get that far.  If it starts easy and you can hand turn it up to bottoming out, it isn't cross threaded.

[David Rase]

Cory Joe, Are you only getting  "fingernail" shaped filings or ribbons?  Based on your comment that your were just snugging up the plug, fingernail shavings tells me interference is happening during seating.  On the other hand, if the ribbons are coming during threading, not seating, then  I concur with Mike's analogy that a small burr on the peaks of the threads is peeling off.    Cross threading would develop some serious galling.

Below is an example of some serious galling.   
   

[Darkhorse]

You didn't say who made your barrel. If it is a Colerain, based on the one that I built with, I expect to draw file the barrel flats, and when the breech plug is removed I expect to find shavings (chips) in the threads.
For about $100. more my Rice barrel had the flats finished and clean BP threads.
This maybe what your seeing, maybe not.

[Cory Joe Stewart]

I think it is the burr issue that you are mentioning.  That is what I thought it was when it happened but laying awake last night got me to worrying about cross threading. 

Does anyone know if you are more likely to see cross threading damage on the male or female threads?

[David Rase]

The thread pitch and diameter are such that it would be pretty hard to cross thread a breach plug.  One trick to keep from cross threading is after you set the plug onto the barrel rotate the plug counter clockwise until you hear and feel the plug drop slightly.  This drop is when the two leads of the threads engage.  Now start threading the plug clockwise.  This technique works for all threaded items. 
One other thing could be the class of fit your threads have.  There might be too much interference.  If you have an adjustable (split) die you can tighten it up just a bit and chase the threads again removing a minute amount of metal thus removing the thread to thread interference.  I have had to do this more than once over the years.
David

[Cory Joe Stewart]

Thanks David,

My brother in law is a mechanic and he mentioned the counter clockwise trick to. 

Cory Joe Stewart

[Jim Kibler]

The thread pitch and diameter are such that it would be pretty hard to cross thread a breach plug.  One trick to keep from cross threading is after you set the plug onto the barrel rotate the plug counter clockwise until you hear and feel the plug drop slightly.  This drop is when the two leads of the threads engage.  Now start threading the plug clockwise.  This technique works for all threaded items. 
One other thing could be the class of fit your threads have.  There might be too much interference.  If you have an adjustable (split) die you can tighten it up just a bit and chase the threads again removing a minute amount of metal thus removing the thread to thread interference.  I have had to do this more than once over the years.
David

That's a great tip.  It even works with wood screws after they've been installed the first time.  This prevents a screw from starting in a different location than the previous installation.  Nothing worse than a shaped head that doesn't line up properly.  I find myself doing this every time I twist in a wood screw.

Jim

[David R. Pennington]

The thread pitch and diameter are such that it would be pretty hard to cross thread a breach plug.  One trick to keep from cross threading is after you set the plug onto the barrel rotate the plug counter clockwise until you hear and feel the plug drop slightly.  This drop is when the two leads of the threads engage.  Now start threading the plug clockwise.  This technique works for all threaded items. 
One other thing could be the class of fit your threads have.  There might be too much interference.  If you have an adjustable (split) die you can tighten it up just a bit and chase the threads again removing a minute amount of metal thus removing the thread to thread interference.  I have had to do this more than once over the years.
David

Sounds like what David says about thread interference. If you dont see any gaps or voids in the male or female threads and you can re insert without prolems it wasn't cross threaded. I had one with voids in sections of the male threads that chipped off on an old barrel. I got nervous about this one and forged a new plug. I found an adjustable antique die the same size as old threads. I think they were 9/16-14.

[ron w]

to cross thread a 5/8 or so thread takes some serious force, there's no way you could start it by hand and have it be cross threaded. galling is not from cross threading, it is from interference of diameters or dissimilar thread pitches. I never see any mention of anti-seize being used on these plugs. a little anti seize goes a long way to eliminate the potential for galling when threads are cut to very close tolerances, as these should be.