notsofast
Member
So one turn that winds up with a snug barrel should leave about.007" b/c gap while 5 thou would be better 7 thou is probably acceptable
Is my math right?
Help with 29-2 loose barrel !
- Thread starter Tritonman92587
- Start date
So one turn that winds up with a snug barrel should leave about.007" b/c gap while 5 thou would be better 7 thou is probably acceptable
Is my math right?
If the barrel is at 12 o'clock (front sight straight up) and you turn it in one complete turn so it is again at 12 o'clock, the forcing cone end will move back .027777777. You need to end up with a gap between barrel and cylinder of .004 to .008 max. To torque up at 12 o'clock a barrel and f ame with nice smooth threads will be hand snug about 9 o'clock.
OP
Tritonman92587
Member
So I received the 29 back from smith this week with a letter stating the barrel and frame threads are stripped and it can't be repaired , the fellownthat sold it to me is offering my $$$ back so I'm going to take him upon that, he's planning on taking it to a local smith near him for another opinion, does anyone know offhand what thread size the frame barrel is ? Thanks guys for all the help
Protocall_Design
Vendor
N frame threads are .670 - 36. That's .670 diameter and 36 threads per inch.
Doug M.
Member
Contact member BMCM and ask him. You will find several strings about his work on 3rd gen auto pistols in the relevant subform, and one about his work on my 625-6 in this subform.
The threads are .670 and 36 to the inch. I have both a tap and a die. Sometimes the threads are actually not stripped so much as the metal displaced and running a tap over or through will move the metal back into place. Sometimes the threads actually are stripped and the metal was torn out. That would pretty much wreck a frame. Finding a extra fine tap slightly larger would be difficult and expensive ( an N frame tap is about $90) so making a helicoil type repair hard and I am not sure there would be enough meat int he frame anyway.Barrels of course are replaceable, but only come with the .670, 36 threads.
I have lent the tap and die out.
I have lent the tap and die out.
Last edited:
OP
Tritonman92587
Member
Thanks you sir , I'm going to let the seller try his luck with his local smith first, I told him if no luck I would be interested in helping recoup some of his investment as a parts gun as I could use a few things off it if it's totally ruined , I may try the tap and die first if I get it back , thanks to all for the responses I'll post again when I find out what his local smith says, hes going to keep me in the loop on it
Really bad news. It might be best to let someone else have a look, but in your shoes, I'd return the gun and look for another one. Even if you can "restore" some engagement with tap and die by "cleaning up" the threads, you will not get it back to what it should be. Ordinarily you would be seeking maybe 75% engagement. Unless you have a good understanding of threading and the necessary tools to gage both the male and female threads, I'd leave that project to someone else. This is one area where "good enough" is just not what you want.
Sorry S&W wasn't able to help. The good thing is there are plenty of nice, nickel, 8-inch 29-2s around, and they usually are not at the top of the price list.
Sorry S&W wasn't able to help. The good thing is there are plenty of nice, nickel, 8-inch 29-2s around, and they usually are not at the top of the price list.
Protocall_Design
Vendor
The only easy fix for that one would be to tap the frame to 11/16 (.687) - 36 and make a custom barrel from a blank. Then you can make the barrel threads anything you want on the blank.
Here is the tap and die for cheap.11/16 - 36 Special Pitch Plug Tap, High Speed Steel and 11/16-36 Special Pitch Round Die, 1-1/2" Outside Diameter - High Speed Steel
Here is the tap and die for cheap.11/16 - 36 Special Pitch Plug Tap, High Speed Steel and 11/16-36 Special Pitch Round Die, 1-1/2" Outside Diameter - High Speed Steel
So 9 o'clock is where it should be hand tight? That seems like a LOT of squish. Given the .028" pitch, that would be 1/4th turn or .007" of metal needing to either compress or move. With threads that fine it just seems like a lot. Needless to say, if that is what it is, I'm good with it. There is way too much knowledge here for me to argue with anyone over anything.
The torque required to tension a 5/8 fine thread B7 0r B16 stud (18 to the inch) to approx 60% yield strength is 126ft/lb. A course thread (11 to the inch) is 111ft/lb. 3/4 fine (10 to the in.) is 198ft/lb and fine (16 to the in.) is 220ft lb.
Blue steel guns are some form of 4140 as are B7 and B16 studs. As you can see as thread pitch becomes finer the torque goes up. .670 is between 5/8 and 3/4 (just under 11/16). My frame wrench only has a 12" handle and I am not getting on it very hard to get that last 90 degrees. Not even close to 100ft lb. By hand tight I mean when the back of the barrel just hits the frame. Not cranked on by hand. I should set up a torque wrench some how and get a reading sometime.
By the way I am currently serving as a final quality control inspector for the bolting in a oil refinery turn around. Just 2 weeks left. Last night I looked at around 80 flange sets, gaskets and their studs. I have to witness the torquing of 10% of the flange sets and sign them off. I usually torque check the bigger flanges which have 20 or more studs. Many floating heads on heat exchanger bundles run 30 or more 5/8 0r 3/4 B7 fine threads. I have to buy off all of those before they pressure test them. The torque wrench for these is a 3/4" drive with about a 3 ft handle. Stud bolts up to about 1 14" in diameter they use air pressure controlled "rad" guns to just5 under 1000ft/lbs, then bigger than that they us slim lines. A slim line uses air to run a hydraulic pump that the pressure can be adjusted on. A small ram in the head moves the "socket" one click at a time. a 2" stud goes from about 4300 ft/lb to around 7200 depending on how much of the yield you want to tension it at. I have worked with 4" studs. Those have 6 1/8 nuts and take about 35,000 ft/lb at 70% of their yield strength.
Some studs are tensioned. Extra length is left sticking out of the nut. Then you thread on a special ram and it pulls the stud to the correct tension then the nut is turned to hold that tension.
I love steel and mechanical stuff, but I am about sick of walking and climbing around looking at studs right now. 2 more weeks and I am probably done working for the year. At my age 10 weeks is plenty.
Blue steel guns are some form of 4140 as are B7 and B16 studs. As you can see as thread pitch becomes finer the torque goes up. .670 is between 5/8 and 3/4 (just under 11/16). My frame wrench only has a 12" handle and I am not getting on it very hard to get that last 90 degrees. Not even close to 100ft lb. By hand tight I mean when the back of the barrel just hits the frame. Not cranked on by hand. I should set up a torque wrench some how and get a reading sometime.
By the way I am currently serving as a final quality control inspector for the bolting in a oil refinery turn around. Just 2 weeks left. Last night I looked at around 80 flange sets, gaskets and their studs. I have to witness the torquing of 10% of the flange sets and sign them off. I usually torque check the bigger flanges which have 20 or more studs. Many floating heads on heat exchanger bundles run 30 or more 5/8 0r 3/4 B7 fine threads. I have to buy off all of those before they pressure test them. The torque wrench for these is a 3/4" drive with about a 3 ft handle. Stud bolts up to about 1 14" in diameter they use air pressure controlled "rad" guns to just5 under 1000ft/lbs, then bigger than that they us slim lines. A slim line uses air to run a hydraulic pump that the pressure can be adjusted on. A small ram in the head moves the "socket" one click at a time. a 2" stud goes from about 4300 ft/lb to around 7200 depending on how much of the yield you want to tension it at. I have worked with 4" studs. Those have 6 1/8 nuts and take about 35,000 ft/lb at 70% of their yield strength.
Some studs are tensioned. Extra length is left sticking out of the nut. Then you thread on a special ram and it pulls the stud to the correct tension then the nut is turned to hold that tension.
I love steel and mechanical stuff, but I am about sick of walking and climbing around looking at studs right now. 2 more weeks and I am probably done working for the year. At my age 10 weeks is plenty.
Last edited:
