Changing 3/8x16 to 3/8x10 - possible ?

Newton

Newton

AzB Silver Member
Silver Member
I have been battling McDermotts proprietary 3/8x16 joint for some time now - having had some customers shafts going through McDermott to get the insert installed... Takes time and is xpensive.

Now I have a friend with a break cue with a 3/8x16 joint and he has asked me about the possibility of change it to "stock" 3/8x10...

Since I'm in the metric world and don't work with the imperials more than I needed to, I feel a little on thin ice here. I may be able to use live tooling for these threads (missing the longer "internal" tool for I.D threading) but would there be enough "hold" in this ? Have some one done this conversion ?

I was thinking, in worst case - I could core out a small portion in the joint area and glue up a new maple core - and then install the 3/8x10 joint.. But I guess this could be week :scratchhead: I would prefer to tap the hole since I'm missing the live tool...

If some one have experienced this conversion or have any thoughts on it - your comments are most welcome.

The cue is by the way a collar free break cue - much like a sneaky p.

Kent
 
"I was thinking, in worst case - I could core out a small portion in the joint area and glue up a new maple core - and then install the 3/8x10 joint.. But I guess this could be week I would prefer to tap the hole since I'm missing the live tool..."

I think this is pretty much the standard approach. If the new core is made to fit well with a good glue bond, I don't see anything weak about it. The same thing will have to be done on both the shaft and the butt, of course.

My 2 cents,

Gary
 
GEBrown said:
"I was thinking, in worst case - I could core out a small portion in the joint area and glue up a new maple core - and then install the 3/8x10 joint.. But I guess this could be week I would prefer to tap the hole since I'm missing the live tool..."

I think this is pretty much the standard approach. If the new core is made to fit well with a good glue bond, I don't see anything weak about it. The same thing will have to be done on both the shaft and the butt, of course.

My 2 cents,

Gary
Click to expand...

Thanks Gary, then I guess my idea is not that stupid as I thought it could be... Hmm, I guess this is easier than starting ordering live tool to machine
over the old threads and possibly loose the wood threads at the end.

Attached is a pic of the cue - brand new.
What the owner would like is to custom make a OB break shaft for this cue with 3/8x10 threads..

K
 

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I did go for the original idea where I removed the pin, bored a 12mm area for a new 12mm tennon which I planned center drilling and threading.
It was a little spooky last night - "where do I stop coring the cues joint area and when do I have enough meat to make the 3/8x10"?

Would 12mm tennon be enough to thread the 3/8x10? Never done this type of repair-so I was just wondering if my judgement was ok or not?

Thanks
K
 
Newton said:
I did go for the original idea where I removed the pin, bored a 12mm area for a new 12mm tennon which I planned center drilling and threading.
It was a little spooky last night - "where do I stop coring the cues joint area and when do I have enough meat to make the 3/8x10"?

Would 12mm tennon be enough to thread the 3/8x10? Never done this type of repair-so I was just wondering if my judgement was ok or not?

Thanks
K
Click to expand...

It is common to plug the shaft with a 1/2 in piece of phenolic and then thread it for 3/8-10. 1/2 in is only a few thou more than 12mm so it should be big enough.

Kim
 
Thanks guys- then I feel I'm on the safe side then. Would try to do the install tomorrow. What do you use to bore the hole to for these threads?
I know, I know-Mr.Google and Chris's book has the number but just curious on what you use:-)
K
 
Newton said:
Thanks guys- then I feel I'm on the safe side then. Would try to do the install tomorrow. What do you use to bore the hole to for these threads?
I know, I know-Mr.Google and Chris's book has the number but just curious on what you use:-)
K
Click to expand...

The most accurate way is to use a small boring bar to make a .312 hole and tap it. Or live tap it.

I use a 5/16 solid carbide 3 flute drill and a 3/8-10 tap from Atlas. It comes out near perfect. I indicate it after I glue it in and I might need to push it a thou or 2 to get it centered. I don't have any problems.

Kim
 
GEBrown said:
Newton,

Here is a thread with lots of information on different ways that guys use to bore holes and cut threads: http://forums.azbilliards.com/showthread.php?t=240548&highlight=drill

I personally drill a 9/32 (.28125) inch hole, ream it true with a .312" reamer that has a 9/32" pilot, and then tap with a 3/8-10 (.312" minor) tap. I use 3/8-10 modified pins.

It works out pretty well.

HTH

Gary
Click to expand...

Im glad my thread can help others, lol. Ive used the boring bar with success, but i ended up buying a 5/16 carbide end mill that makes a perfect hole, dead center, and very precise. Its much easier than boring. Im very grateful to all who helped me figure it out and guided me down the right path.

Joe
 
snipershot said:
Im glad my thread can help others, lol. Ive used the boring bar with success, but i ended up buying a 5/16 carbide end mill that makes a perfect hole, dead center, and very precise. Its much easier than boring. Im very grateful to all who helped me figure it out and guided me down the right path.

Joe
Click to expand...

FWIW 5/16 end mill would be oversized for the .308 minor 3/8 10 but because the barrel is .382 and you bore for that barrel, oversized hole for the threads works. It gives more " wiggle" room and glue space at the bottom.
 
JoeyInCali said:
FWIW 5/16 end mill would be oversized for the .308 minor 3/8 10 but because the barrel is .382 and you bore for that barrel, oversized hole for the threads works. It gives more " wiggle" room and glue space at the bottom.
Click to expand...

Thanks Joey. I didnt realize that. I bought a 3/8 end mill to make the cut for the barrel, and it fits very snug. I put a pin in to test the fit, and had to use pliers to get it out. Lol. Of course i wrapped some leather around the pin first to keep the pliers from damaging the threads. So i guess i better not try using that 5/16 end mill if i plan on using a regular pin then. Thanks again man. I appreciate it.

Joe
 
Thank you all for your feedbacks.
I'm in the metric world as mentioned and only have precision tools for mm coring and drilling.
So I would use my boring bar to do this and see how it goes. I'll drop a pic up here by the end of the day when this is done.
Thanks

K
 
Ahhh.... Bugger!
Center drilled and bored with a 8,5mm !!!!!
Another confirmation that I'm no good early in the morning - definately a C or D person.
Have to core out again and then new tennon...Arg arg:-(
 
Sounds like you need one of my boring bars that can drill and bore the hole that you need for tapping.
Neil
 
Hmm, job done but a real pain.
Center drilled, drilled with 7,5mm and reamed 5/16.
Then tapped with Atlast tap.
However I did not check the tap when I cored-I made the depth 100 accurate to get 29mm joint sticking out.
Well, the tap tid not tap to the bottom of the hole si I had to RE-BORE after I had made the first tap. This to alow the tap to "overshoot" the depth so I could install the joint as deep as needed.

This did of course not help on TIR where it all in all seem to have a whopping 0,0039" (0,1mm)! Currently sipping a soda and scratcing my head trying to figure if I blew it. Have tried to index it but it seems to go back, but I have left the lathe holding the pin indexed.

I think I have been a little to tight on the dept where the pin is installed to the bottom- hence no indexing possible.

I guess I have to custom make a shaft with oversized threads to get out of this one-or do it all over again for the third time:-(

Neil, could you drop me some pics on a email regarding that tool?
I'm rubbish resharpening Carbide so I have invested in boringbars which I can change the tips on. Workes so far.

Think it's time for one of those brown ones-cerved chilled in pubs- and think through my options.
Have a nice weekend friends.

K
 
Newton,

If it had gone well/perfect the first time you wouldn't have learned anything - but now you have!! That's good!

Yes, you have to overshoot the tap hole so that you can get threads all the way down that you need - OR - get a "bottom" tap where there is no taper at the front of the tap, just threads all the way. You can make a bottom tap by grinding off the front end of a regular tap. You thread with the regular and then you go back with the bottom tap to finish it out.

3 attempts is not that bad!! Many of us have done that or worse!!:yikes:

But definitely head down to the pub and have a beer or two and relax.

Beer makes everything better!! (Well, almost :smile:)

Keep up the good work!

Gary
 
Thanks Gary.

Normally we usr 3 taps in the metric world where one has a large taper, midle - less and the last one being a bottom tap. The midle one is skiped often.

I think I would order live tools for my metric threading. The lathe can in some funcy way make imperials-but I think (guessing) that require a cogwhele change which is a pain.

I glued up a shaft after my last post. Same operation - with a tennon in the back (this was a damaged shaft) and try to fix this tomorrow. Not sure if that TIR would make the cue woble like a dogs bone.

Firs cold one jacked now-and it helps ;-)

Kent
 
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