Advice on CVA nipple threads striped

[william cook]

I need advice on which way I should go to repair the bolster on my CVA Frontier.After some research there look's to be a couple of options,7-1mm or a TC 1/4 x 28 nipple.I could go either way, just need to know if one is better than the other.Thank's,Bill.

 

[matt denison]

I've repaired a coupla these using 1/4 x 20. Taps, #3 drill bit, and nipples are easy to get, simple. I use a drill press. I have a technique that is fool proof. If you want to hear it let me know, I'll post it here.

 

[william cook]

I am open to any help I can get!Thank's,Bill.

 

[william cook]

I have a 1/4"X 20 tap that say's to use a #7 drill bit.A 13/64th" bit works(I tried it on a scrap piece of metal)but,it just spins around in the nipple seat hole. :idunno: By the way the threads are "stripped" not "striped" Bill.

 

[necchi]

There isn't enough metal left to re-tap the threads.
The major thread of the metric is larger than the minor thread of the national. (period)
You could cut the threads but they won't be standard.

Two options; http://www.trackofthewolf.com/Search.aspx?search=Drum-cva
The untapped for nipple will allow better indexing for the finished installed nipple.

There is an inherent risk with these too, they are after market and don't have any liability guarantee,

 

[Zonie]

A #3 (.213) drill is the tap drill size for a 1/4-28 thread.
The 1/4-20 thread uses a #7 (.201) tap drill.

The CVA Frontier came with a M6 X 1 threaded nipple.

This 6 mm thread has an outside diameter of 6mm (.236 inches)

Notice that neither # tap drill is as large as the 6mm thread so neither will remove all of the old damaged metric threads.

When the metric threads were made, material was removed from the female thread to clear the male thread. These areas where the old threads existed will not contribute to the strength of a newly made 1/4 inch thread.

That said, I can't find any commercial nipples with a 1/4-20 thread so tapping the old nipple hole with this size tap will prepare the hole for a non existent nipple.

The hole could be threaded for the 1/4-28 sized nipples but be aware. The threads will not be as strong as they should be because some of the material that forms the minor (smallest) diameter doesn't exist.

A better plan is to thread the old hole with a 1/4-32 UNEF thread.
There are nipples available for this thread size and its larger minor diameter is larger than either the 1/4-20 or the 1/4-28 thread.

The 1/4-32 thread also uses a #3 tap drill but the increased thread count will improve the strength of the threads which will make up (slightly) for the missing drum material.

 

[Ken Cormier]

Cool info thanks for posting. :thumbsup:

 

[william cook]

Thank's so much for that information,I have yet to measure the hole as it could be the previous owner installed the wrong nipple.There are threads left in the bolster(?)but they are damaged from corrosion.(The suspect nipple blew out of the gun at the range and was lost.)

 

[william cook]

Track of the wolf offers a 7mm nipple(as a repair for CVA rifles) that would be a hair larger than 1/4".My question would be,since the original size was 6mm and the new size is also in mm,can I just run a 7mm tap through the hole and use the nipple Track has? Thank's,Bill.

 

[hawkeye2]

1mm = .039", you do the math. You would need a tap in the final size as well as a bottoming tap or you could just cut the tap off after you started the tapping to make a bottoming tap. The thread pitch would have to be very close to the existing pitch

5/16-24 is the standard thread for US military muskets and nipples are readily available in steel, SS, and bronze to take #11 or musket caps. Do you have enough room in the drum to go that large?

 

[william cook]

Well,after measuring the hole I felt there was enough "meat"left to go to 7mm.I called Track of the Wolf and the man said I could just tap it with a 7mm without any drilling.So,took a trip into town and bought a 7mm tap,tapped the hole and it look's like it will work!I ordered the 7mm nipple and will update you all on the outcome! :grin: Thanks to all who responded to my cry for help!! Bill. :hatsoff:

 

[necchi]

Sounds like a good fix :thumbsup:
This is the first I've heard of a 7mm nipple for this kind of issue, it makes complete sense for a fairly common problem.
Please do keep us posted.

 

[gunmaker43]

you mite want to stamp the drum 7mm for someone in future....Tom

 

[william cook]

Good advise,Thank you! Bill.

 

[william cook]

I can't spell,Good "advice"!

 

[william cook]

I got the 7-1mm nipple from Track and it worked great!! :grin: Now am waiting on the LMF brown to come in and the old Frontier will have a new look. Bill.