Repairing Nipple hole for buddy?

[kmeyer]

Hi all! A friend of mine is starting a project of refinishing his dads percussion pendersoli double-barrel smoothbore. He tried to remove both nipples and one came out easily. The other was so corroded it snapped. He was able to drill it out and asked me to re-tap it.

I was able to re-tap it (1/4-28), but when he drilled out the nipple, he opened the top too wide and the threads will not catch.

I feel like I have two choices and the first may not even be a option. I don't know:

1. Find a nipple that has about twice the ammount of threads. (If they make these it may work because the threads go pretty far down).

2. Open it up to the next common size? (maybe 5/16-24?)

If I go that route, should I do them both or leave them different. He does not plan to shoot single projectile. His plan is to shoot shot for small game type shooting.

Thanks in advance for any input!

 

[flaming canvas]

You can get oversize nipples on the 28 thread. Up to .020 over I think. totw has the taps as well.

If that isn't big enough, the 5/16 may be where you have to go.

 

[Dave K]

If that doesn't work or you would rather have matching nipples(who doesn't). You could have it mig welded and then redrill and tap.

 

[jbullard1]

How about a 1/4x28 Heli-coil thread repair

 

[Zonie]

IMO, a heli-coil is a "last disparate chanch" method that should be considered only after trying the oversize thread nipple method.

Track of the Wolf has both 1/4-28 UNS* nipples and the taps for them that range from .005 to .035 oversize in .005 increments.

Based on the description of the problem I would start with the .020 oversize and then go with the .025, .030 and .035 only if needed.
zonie

* UNS is the designation for Unified National Special for threads that do not have standard major diameters or thread pitches.
Don't worry about it though. The folks at TOTW probably don't know that so just go to their website and order by their part numbers. :grin:

 

[kmeyer]

Hey...Thanks all. I think I'll try the oversize route. By oversize, does this mean the lower part of the nipple with threads is longer?

 

[CoyoteJoe]

It means the diameter is larger, the threaded portion of the nipple is still the same length. They (TOTW) do offer some long shank nipples for underhammer rifles but I think the oversize is the way you want to go.

 

Dixie Gun Works makes repair kits for just this situation. They contain a series of nipples in increasing sizes of the same thread pattern. You keep going up until you hit the size that seals.

This used to be a very common problem when repairing origionals.

 

[JOHN L. HINNANT]

Good Morning Kmeyer,

Nipples with various 1/4-28 thread lengths are availabe.

I suggest you try that route first. Determine how much extra thread length you can use, and contact some of the usual suppliers.

If that does not work, let me know. I will put you in touch with a friend that has some of the original Treso nipples with varying thread length.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

Politicians LIE!!! USA Freedoms DIE!!!!

 

[Pork Chop]

IMO, a heli-coil is a "last disparate chanch" method

I do NOT want to start a big brouhaha over this, but why is that a last desperate chance? They have been used in some pretty high stress applications with outstanding success.

 

[Nor Cal Mikie]

I would guess that the fact that you have to drill out the original threads,or what's left of them, then tap new threads (larger) to the size of the helicoil tap would cut down on the metal that you have to work with. :nono:
.010 to.020 larger is a lot easier to deal with than drilling and tapping oversize, anyday!
Use the "helicoil" as a last resort! :wink:

 

[Zonie]

Of course I agree with Nor Cal Mikie :grin:

A percussion nipple requires a good flat surface to seal against and when a Heli-Coil is installed there is little if any flat surface left.

During the great debate on Green Mountain's "fix" for their thread problems by using a Heli-Coil some people mentioned that they work with spark plugs so I made a scale drawing showing how a spark plugs large sealing surface will seal even with a Heli-Coil but a percussion nipples sealing with a Heli-Coil is marginal at best.

In this scale drawing you can see that most of the area under a nipple is nothing but threads.

Often there is little material around the nipple hole to drill and tap a hole which is large enough to accommodate a Heli-Coil.

Heli-Coils are rather long and there is a possibility of blocking off the flame channel in the gun if it is located closer to the surface than the Heli-Coil is long.

A Heli-coil also is very obviously a "fix" while some oversize threads aren't quite as obvious so from an aesthetic point of view I would prefer plain threads.

Notice that I didn't say a Heli-Coil wouldn't work. I just said IMO it would be a last resort fix.

 

[Pork Chop]

Helicoils are used in the aerospace industry where MORE strength is needed than the base material can support. The threads in a helicoil are more consistent and harder than the original threads. The length is not an issue as you cut them to the length required.

I don't have a dog in this fight, but from what I have read on Helicoils and other products of that nature, they are actually stronger than the OEM holes.

Thanks for your perspective though.

 

[rkeltner]

i figure i ought to put my two bits in on this one. i work in the production machine trades(jet engine manufacturing), and while heli-coils may be used in softer metals for re-enforcing, where the base metal is of reasonable strength, there is nothing to be gained by using them. IMO, if there is enough metal to do so, your best bet would one of the sleeve style thread replacements. additionally, the sleeves use commonly available taps for the threading of the hole to be repaired, and, through most machine supply houses, the initial investment is less. as a postnote, my experience with heli-coils has been that if the part is to be assembled and left, they are fine, but if they are to be assembled and reassembled, the heli-coil will start to create problems, in the form of coil loosening(in the repaired hole) and not wanting to release the screw(nipple in this case) as a final note, i would be concerned with corrosion in the case of the heli-coil, as you are introducing multiple nookes and crannies for fouling to get into. with a sleeve, you can lock-tite the threads, and should not have much trouble!

 

[John Taylor]

Zonie and fixit have the right answer. I have fixed several nipple holes over the years by making a threaded insert and holding it in with loctite. Heli coils are great for things like car engines and small aluminum engines where you want them to stay together. The heli coils that I have used are stainless and can gaul if the parts are taken apart often.

 

[kentucky bucky]

I used the "over sized" method of fixing an old ML double barrel. I got the largest diameter that would start in the holes, and because the nipples were much harder than the breeches I actually cut in the threads as I installed them. I took it slow with lots of oil and went back and forward until they bottomed out. It made a very snug fit.