Secrets Of The Houston Warehouse

Using some conjecture, think about a pressure trace system. You wrap a gizmo around a barrel or tape it to, then pull the trigger and see the resulting size change with the said gizmo. As the barrel expands cause there's a boatload of pressure, this thing quantifies it real fast like.

Ok, so if you can see that change up where only the bore size is offering surface area for pressure to push on, what do you suppose happens at the thread joint. Yes, a portion of the case is not inside the threaded area. But a good bit of the case IS inside there. So, you are at a point where internal surface area is at its greatest, and surrounding metal is at its least.

Jackie, as to the barrel coming "Loose". Harold did that test too, and found that indeed, they did loosen up. He did this by testing removal torque before and after firing. So, while it didn't unscrew, the thread metal inside did deform measurably and cause the joint to not be as tight. Same as "loosening".

Then, I think your statement above about tightening barrels for other competitors demonstrates some truth in what mikeinco says about shooters not having barrels tight enough. I'm not gonna say a majority, but, there are some who think hand tight is good enough,and that's simply foolishness. It's good enough if nobody else knows how to shoot, otherwise, yer gett'n yer ass handed to ya...
 
I SUPPOSE WHAT WE NEED IS SOMEONE TO DO THE MATH.
i did my 300 win mag /rem 700 bbl torque at 150 if i remember correctly. i did no math, i took the 125 that jackie used and added some...plain and simple. call it prior experience. same basic joint size, lower or similar pressure,heavier load.
inline with jackies comments, on high temp/high pressure closed systems, one torque method is to preheat the studs for 24 hours, a specific torque is then applied and the assembly allowed to cool. the actual end torque is determined by engineers in a lab, the field guys just follow the instruction.


and yes i have the book.

mike in co
 
With all respect to Mr Vaughn, I find it takes more force to break a barrel loose than I exerted when tightenning it.

Of course, there are other factors involved.

One of the biggest culprits in the improper application of of threaded joints is when the mating surface, ie, the reciever face and the barrel shoulder, are not perfectly square and truly straight with the pitch circle of the thread.

As I said before, many of the maladays that are attributed to other causes can be traced back to nothing more than poor machine shop practice........jackie
 
ok guys i did some math...generic, not specific but pretty close.
on a 1 1/16 threaded fastener torqued to 150ft/bs produces a 700 lbs clamping force on the joint...bbl to recver faces.

in the example of vaughn's 31000lb preload, in a normal condition , this would require a torque of 6000 plus ft/lbs. as has been noted, there are ways of increasing final torque/load by heat or strech.......i wonder how he came up with that number ??

seems excessive

mike in co
 
mike in co said:
ok guys i did some math...generic, not specific but pretty close.
on a 1 1/16 threaded fastener torqued to 150ft/bs produces a 700 lbs clamping force on the joint...bbl to recver faces.

in the example of vaughn's 31000lb preload, in a normal condition , this would require a torque of 6000 plus ft/lbs. as has been noted, there are ways of increasing final torque/load by heat or strech.......i wonder how he came up with that number ??

seems excessive

mike in co
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Mike, your math is off by about 1000 miles.... Think about it. 150 pounds pulling on a 1 foot long wrench, and you're thinking it generates 700 lbs of endload? There's a lot more than a 5:1 ratio of wrench force to joint load.

I think Vaughn used a constant for friction, and also has an entire chapter on reducing that friction with various lubes. That's another story altogether. But, your joint has 10's of 1000's of pounds of load on it.

Jackie, his comparisons were the difference between a fired rifle and an unfired one.

Charles, My feeling on Loctite is, it's great for helping things to not unscrew. If the joint isn't doing that, then loctite ain't gonna do a thing. Sorta like scope rings. People think somehow that Loctite will make a screw hold better (or god knows what). No, it'll just keep the screw from turning out. Doesn't hole 1 bit better, in fact, in the wrong places, it's worse. It really doesn't take up space in there at all. When you consider that the forces involved are enough to stretch the steel of the barrel and action, it then follows that a bit of Loctite won't stop anything else.
 
your ignoring a bunch of stuff with that simple reply.....
so yes i do.......

i used a simple torque clamp calculator, did not get into metal alloy.( the calculator probably assumes a 7or 8 thread, not our 16..but still close)
not off by 1000 miles at all

mike in co

4Mesh said:
Mike, your math is off by about 1000 miles.... Think about it. 150 pounds pulling on a 1 foot long wrench, and you're thinking it generates 700 lbs of endload? There's a lot more than a 5:1 ratio of wrench force to joint load.

I think Vaughn used a constant for friction, and also has an entire chapter on reducing that friction with various lubes. That's another story altogether. But, your joint has 10's of 1000's of pounds of load on it.

Jackie, his comparisons were the difference between a fired rifle and an unfired one.

Charles, My feeling on Loctite is, it's great for helping things to not unscrew. If the joint isn't doing that, then loctite ain't gonna do a thing. Sorta like scope rings. People think somehow that Loctite will make a screw hold better (or god knows what). No, it'll just keep the screw from turning out. Doesn't hole 1 bit better, in fact, in the wrong places, it's worse. It really doesn't take up space in there at all. When you consider that the forces involved are enough to stretch the steel of the barrel and action, it then follows that a bit of Loctite won't stop anything else.
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Mike, just quickly.

If the wrench is 12" long, and there's 150# of force on it.

The end of the wrench will travel 24 * pi = 75.3982" for one revolution.

The barrel will move 1/16" on a Remmy, (or 1/18" on most customs).

Completely ignoring friction (which I'm certain Harold didn't do)
150# *75.3982 / .0625 = 180955#

Then factor for the amount of friction and reduce by that, and you'll come close. I'm sure you can google that and come up with a decent guess.
 
mike in co said:
your ignoring a bunch of stuff with that simple reply.....
so yes i do.......

i used a simple torque clamp calculator, did not get into metal alloy.

mike in co
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Where is the calculator you used? Of course, I have to get back to work so I can't reply again... Something is seriously wrong.
 
you are leaving out the thread angle for one....

mike in co
 
if your math is right..that is the radial force, not the axial force....
mike in co

4Mesh said:
Mike, just quickly.

If the wrench is 12" long, and there's 150# of force on it.

The end of the wrench will travel 24 * pi = 75.3982" for one revolution.

The barrel will move 1/16" on a Remmy, (or 1/18" on most customs).

Completely ignoring friction (which I'm certain Harold didn't do)
150# *75.3982 / .0625 = 180955#

Then factor for the amount of friction and reduce by that, and you'll come close. I'm sure you can google that and come up with a decent guess.
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mike in co said:
if your math is right..that is the radial force, not the axial force....
mike in co
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That's where the .0625" comes from Mike. 1/16" = .0625 = how far the barrel moves axially for each turn of the barrel. It's just a convoluted "lever" is all it is. At the same time, you are up to where you need 150# of force to move the wrench which is 12" from the centerline of the barrel (ft lbs).

Yes, there's a lot of force eaten up with friction, and that reduces the efficiency that makes the ratio I show. But the idea is still the same. It's just that friction is a BIG hunk of the pie.
 
http://www.engineersedge.com/calculators/torque_calc.htm

This calculator gives 8500 lb of axial force in the threads of a 1.0625 barrel torqued to 150 ft lb. Compare this to 10500 lb force from 60 kpsi chamber pressure on a 0.473" BR chamber and 9100 lb on a 0.44" PPC chamber. This suggests both are momentarily "loose" during firing. The calculator assumes dry threads.

For lubed threads, the K factor decreases from 0.2 to 0.18, so the thread force becomes 9400 lb. Then the BR comes loose and the PPC doesn't.

Jackie, I don't mean to argue with your experience, just reporting what the math says.

Cheers,
Keith
 
That calculator never takes the thread pitch into consideration??? Not sure what that's all about. But, I'm pretty sure 1tpi won't generate the same axial load as 36tpi using the same torsional force.


Mike, if you used a similar calculator, note the torque is in inch pounds, not foot pounds.
 
so now calculate the actual load on the various parts......cause 60kpsi is not force on the bolt head. you are ignoring the case on the walls of the chamber. ignoring the fact that there is only a small primer hole, that the case is much thicker at the base and that there is only a small time frame that pressure hits 60kpsi.......little gets to the bolt head.

mike in co

ps his 8500 is correct...i had divided by 12 ..an error on my part

mks said:
http://www.engineersedge.com/calculators/torque_calc.htm

This calculator gives 8500 lb of axial force in the threads of a 1.0625 barrel torqued to 150 ft lb. Compare this to 10500 lb force from 60 kpsi chamber pressure on a 0.473" BR chamber and 9100 lb on a 0.44" PPC chamber. This suggests both are momentarily "loose" during firing. The calculator assumes dry threads.

For lubed threads, the K factor decreases from 0.2 to 0.18, so the thread force becomes 9400 lb. Then the BR comes loose and the PPC doesn't.

Jackie, I don't mean to argue with your experience, just reporting what the math says.

Cheers,
Keith
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4Mesh said:
That calculator never takes the thread pitch into consideration???
Click to expand...

Yeah, that is always a surprising result, but if you derive the formula from first principles, the thread pitch cancels out.
 
hmmmmmmmmmm
tell me if i am wrong, but this additional stress on the joint, does not proove it is "lose" at anytime...
yes no or is it just because it is not at its original prestreed condition, that some are calling it lose.....
as jackie has pointed out and most of you have seen, it takes considerable more force to break a joint free than it does to put the joint in its original torqued condition....
mike in co

mks said:
http://www.engineersedge.com/calculators/torque_calc.htm

This calculator gives 8500 lb of axial force in the threads of a 1.0625 barrel torqued to 150 ft lb. Compare this to 10500 lb force from 60 kpsi chamber pressure on a 0.473" BR chamber and 9100 lb on a 0.44" PPC chamber. This suggests both are momentarily "loose" during firing. The calculator assumes dry threads.

For lubed threads, the K factor decreases from 0.2 to 0.18, so the thread force becomes 9400 lb. Then the BR comes loose and the PPC doesn't.

Jackie, I don't mean to argue with your experience, just reporting what the math says.

Cheers,
Keith
Click to expand...
 
Actually, in this case to deformation is most likely in the threaded hole (action ring) not in the bolt (tenon) which raises in some interesting scope base alignment issues....

al
 
going back the the bolt/case head...more errors..
the case head is two things the brass case head and the primer.
your use of the case head area and 60kpsi is in error. the pressure is on the inside of the case and the surface area INSIDE case and the head end is significantly less than the flat of the brass outside at the base. additionally the surface area of the primer needs to be removed as it see its pressure metered thru the flash hole.
and then remove from the equation the area of the firingpin hole in the bolt, its only primer pressure but still got to remove some...

if this had been a double ended pistion the math works, but it aint.

mike in co
 
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