Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Gunsmithing


Reply

Torque Recomendations

 
LinkBack Thread Tools Display Modes
  #15  
Old 10-25-2011, 09:32 AM
Platinum Member
 
Join Date: Jul 2004
Location: Texas
Posts: 5,374
Re: Torque Recomendations

Quote:
Originally Posted by NesikaChad View Post
Reason I asked:

I was faced with this back in 2004. I have a friend in the Seattle area who's an ME. He put me in contact with a colleague of his who's sole job in life is developing fasteners for airplanes.

He was kind enough to work up a full evaluation based on an assortment of fasteners I sent him. Some were from Brownells and stuff made in house.

After all sorts of testing he wrote me a full report on this.

40lbs. No more, no less. More yields the threads. Less doesn't do the job.

If it takes more than 40, something is wrong. I'd start with the stock.

The issue lies in the loading on the thread flanks. A screw is a spring for all practical purposes. Your putting the fastener under tension so that it pulls the receiver into the stock. If the load exceeds the capacity of the threads, it will yield and the tension erodes. Not necessarily all at once either. The loading also needs to deliver a sufficient amount of friction so that the fastener stays put. Especially when subjected to vibration. Surface finish has a lot to do with this too. So does the class of thread but I don't get too overly concerned with that part. It is just a dumb guard screw after all. I'd have to dig up the paper, but if memory serves me correctly, 40lbs delivers something like 1600lbs of tensile load. This loading has to be factored based on the root diameter of the fastener. To put this in simple terms. Imagine a bolt measuring an inch in outside diameter. If we were to put some sort of ridiculous pitch on it that resulted in the minor diameter measuring at a 1/2" we couldn't generate calculations based on the outside diameter. The bolt would fail. Pitch and flank angles also plays into this but that's getting really silly.

Keep in mind also that 40lbs,50, or 60 is sort of a misguided way to do this stuff. Friction will skew the desired result. A screw made from 303 series stainless is quite gummy/sticky compared to one machined from 4140 heat treat. Stainless fasteners in stainless actions only accentuates the effect. Lube on the threads may help some. If we can grease up a barrel tennon, stands to reason you can grease the guard screws. don't forget under the head of the screw also as it has quite a bit of surface area as well. This is one reason why in auto racing things like rod bolts aren't torqued anymore. They measure the elongation of the fastener when it's placed under load. The "stretch" has been calculated to deliver the appropriate amount of tension to ensure the rod cap stays put. Torque to yield fasteners kinda fall into this realm too.


I've used 40lbs for at least 8 years now. Never once has it failed me. I spent 3 years in Iraq as a security contractor. I was also the chief armorer/firearms instructor at the US Embassy in Baghdad. I bring this up because I heard all sorts of rumors about M40's having issues with zeros.

Guess what the Marines preach? 65lbs.

I always wondered if that had something to do with it.


Take it for what its worth. Just thought I'd share that.


C.


Chad Dixon
Owner/Gunmaker
LongRifles, Inc.
Very good Info Chad.

I do treat stainless screws differently than heat treated screws by using anti seize compounds
on them. (An example is stainless muzzle breaks on stainless barrels).

When you said 40 lbs I assume you meant 40 inch pounds.

I have heard of people using over 100 ft/lbs on a barrel to reciever connection because the threads
are rated higher, but there is a reasonable limit to all torque values,And this is where experance
comes in.

As far as limiting myself to 40in/lbs on the bedding screws I have some rifles that will shoot lose if
torque is set at 40 but when increased to 50+ this probablem stops, so I leave my options open.

Thanks
J E CUSTOM
__________________
"PRESS ON"
Reply With Quote
  #16  
Old 09-04-2012, 12:05 PM
Silver Member
 
Join Date: Oct 2006
Posts: 455
Re: Torque Recomendations

I look up the max torque for that screw size.
Then I have to know what grade screw it is.
Then I have to measure how much engagement with the female threads.
Then I have to evaluate the female material; Steel is best, but it may be cast iron or Aluminum.
If engagement is more than 1.5 times the root [minor diameter of the screw] the screw is probably the weak link.
Then I have to evaluate the lubrication. Wax makes for much more tension from the same torque. Oil and grease not so much. Clean and dry is the least.
Then I calibrate the torque wrench. I use as standards, a ruler and a weight that I weighed on a balance beam.
Then I do a destructive test on sample material to verity my calculation is correct. If the female is the weak link, I mill sample material to the same thickness.


Most guys just want a recipe answer.
Reply With Quote
  #17  
Old 10-27-2013, 11:12 AM
Silver Member
 
Join Date: Oct 2013
Location: Yellowknife, NT Canada
Posts: 100
Re: Torque Recomendations

Good info. Thanks.
Reply With Quote
  #18  
Old 10-28-2013, 10:01 AM
Official LRH Sponsor
 
Join Date: May 2011
Location: Ventura CA
Posts: 787
Quote:
Originally Posted by J E Custom View Post
Scope base screws 30 inch-lbs "MAX"
Windage screws 30-40 inch-lbs "MAX"
Scope ring screws (Aluminum Rings) 10-15 inch-lbs "MAX"
Scope ring screws (Steel Rings) 15-20 inch-lbs "MAX"
Note' If scope base and ring Screws have less than 5 threads of engagement they should be replaced with longer ones.
30 inch-lbs for #6 base screws seems too high, especially when #8 ring screws in steel get only 15-20 inch-lbs.

I would recommend reversing the values:
#6 base screws 20 inch-lbs
#8 ring screws (steel rings) 30 inch-lbs

That's what I use and it keeps me out of trouble.
__________________

www.HighPowerOptics.com
Sports Optics
Rifle Scope Installation Tool Kits for Rent
Reply With Quote
  #19  
Old 10-28-2013, 02:58 PM
Platinum Member
 
Join Date: Jul 2004
Location: Texas
Posts: 5,374
Re: Torque Recommendations

Quote:
Originally Posted by bruce_ventura View Post
30 inch-lbs for #6 base screws seems too high, especially when #8 ring screws in steel get only 15-20 inch-lbs.

I would recommend reversing the values:
#6 base screws 20 inch-lbs
#8 ring screws (steel rings) 30 inch-lbs

That's what I use and it keeps me out of trouble.


Those are MAX Torque values and should be reduced unless you are having trouble with them coming loose. Any more torque, and the screws should be replaced every time the scope bases are removed.

This is also with a minimum of 5 threads of engagement and on steel (Not Aluminum).


J E CUSTOM
__________________
"PRESS ON"
Reply With Quote
  #20  
Old 11-07-2013, 06:30 AM
Platinum Member
 
Join Date: Dec 2008
Location: Great Falls, MT
Posts: 4,359
Re: Torque Recomendations

This should be in the "sticky" section!
Attached Thumbnails - Click to View Larger
Torque Recomendations-thumbs-up-sign-thumb8413541_zps85645168.jpg  
__________________

I voted for my "FREEDOM", "GUNS", and "MONEY" - keep the change - UNK.



"I am always proud of my country!"

"Leadership Rule #2: Don't be an @zzhole." - Maj Gen Burton Field.
Reply With Quote
  #21  
Old 11-07-2013, 10:05 AM
Platinum Member
 
Join Date: Jan 2004
Location: Blackfoot, Idaho
Posts: 8,047
Re: Torque Recomendations

Quote:
Originally Posted by FEENIX View Post
This should be in the "sticky" section!
FEENIX,

What you said, even louder!!!!

Good find.
__________________
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Torque Recomendations
Thread Thread Starter Forum Replies Last Post
Scope recomendations please James Jones Long Range Scopes and Other Optics 7 04-17-2014 12:00 PM
WY/MT/ID trip recomendations Forester West 5 06-12-2008 06:26 AM
Chronograph recomendations Happ571 Reloading 38 05-25-2008 11:53 PM
new rifle recomendations ven Long Range Hunting & Shooting 14 08-18-2007 10:39 PM
Beyond Recomendations? littletoes Equipment Discussions 5 04-28-2002 09:20 AM

Current Poll
Are you on Facebook?
Yes - 46.60%
1,091 Vote
No - 19.22%
450 Votes
No, but I may join - 1.75%
41 Votes
No way, are you kidding? - 36.14%
846 Votes
Total Votes: 2,341
You may not vote on this poll.

All times are GMT -5. The time now is 03:35 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC