Maybe someone can splain this

[JerrySharrett]

Wilbur

Had you threaded the piece, the forces would have been spirally confused.
.

I knew a guy once that had a threading machine that was an inch longer and a half inch taller than when he bought it....

Is spirally confused anything like radially exonerated?

I think we are getting closer to the "hammers of hell" bolt handle tuner.

BTW, who was it at the Shamrock that was selling the fast-load blocks that bolt onto the front rest??

 

[Bob Dodd]

Yep

Wilber is correct about the threads and the heavier the thread the more the ID changes. I run bushing on a cleaning rod all the way in my barrels to check the bore tapper, most have 1 to .0002 tapper.

 

[pacecil]

Thanks Al...

For those who want to figure it themselves (lucky shooter), heres the math:

Stress S in bore with external pressure P: S=2P[d^2/(D^2-d^2)]
If you work this out for a barrel with o. d. D of .90" and i. d. d of .24" and external pressure of 5000 psi, you come up with an internal compressive stress of 765 psi.

Contraction of the i. d. will be e, where e=765/30,000,000 x .24 = .000006"

 

[Mike Marcelli]

pacecil is spot on.

Here is the effective stress in a cylinder with 1000 psi of external pressure. The ends are free and unloaded. The maximum stress if 1952 psi. The properties of the cylinder are:

416 Stainless Steel
Modulus of Elasticity = 29,000,000 psi
Poission's Ratio = 0.29
Density = 0.278 lb/in^3
ID=0.243 in.
OD=0.875 in.
Length is not needed

This chart shows the change in the ID and OD diameters for three different pressure loading conditions up to 10,000 psi of pressure.

This shows the mesh detail and the maximum effective stress of 1604 psi for and internal pressure of 1000 psi.

Finally, for those who want the equations to solve for the maximum principal stress and deformations here is a link to a large picture file of page 308 from Roark's "Formulas for Stress and Strain 4th Edition 1965.
http://www.varmintal.com/page308.png

However, the loading on the barrel stub in the original question was from chucking the barrel stub in (I assume) a 4-Jaw chuck. That loading condition is different than a uniform external pressure. When I get a chance, I will run the calculation for the chuck's loading condition with the pressure applied to four equally spaced areas on the OD. But there is no way to actually know the load from the description given.

Good Hunting... from Varmint Al

Al:

It was a three (3) jaw chuck. Unfortunately, I don't know load on the system, nor do I have the data to allow one to calculate the load. Thanks for your work.

PACecil:

Thank you also. I believe the change you calculated would fall into the category that some, including myself, refer to as "worry data." It also offers an explanation as to why the pin didn't stick after the pressure was applied, i.e., the difference between the initial pin clearance and the final pin clearance (after compression) was greater than .000006."

 

[jackie schmidt]

Pacecil

That is 6 digits to the right of the decimal.
Maybe all of these shooters are searching for a problem that does not exist. And it seems that one has even come upwith a solution to the non existant problem.
I think I will continue to thread my barrels for my tuners just the way I have been doing. I think I can live with a .000006 inch change.........jackie

 

[cpeters]

That is 6 digits to the right of the decimal.
Maybe all of these shooters are searching for a problem that does not exist. And it seems that one has even come upwith a solution to the non existant problem.
I think I will continue to thread my barrels for my tuners just the way I have been doing. I think I can live with a .000006 inch change.........jackie

I'm out of my league here, but below is from the broughton barrel web site:

Broughton Rifle Barrels are crafted from the finest material made today, 416R Crucible Stainless Steel. They are pulled button-rifled,Double stressed relieved at the mill & triple stress relieved in our shop at Broughton Rifle Barrels. Then each barrel is hand lapped with a uniform land and groove diameter up to 0.0001" from breech to muzzle. Our muzzle is NEVER larger than our breech. The exterior of the barrel can be finished to your specifications from rough turned to a polished finish.

Looks like the tolerance of the bore from breech to muzzle of a great barrel doesn't go past 4 decimal places anyhow.

Charlie