Inch pounds torque wrench
- Thread starter TAJ45
- Start date
I use the Borka torque wrench. Fits easily in my kit and works very reliably. [br]
http://www.borkatools.com/pages/atd12/mtsd.html
http://www.borkatools.com/pages/atd12/mtsd.html
Either of the above recommendations will work fine, as will any decent quality inch pound torque wrench.
While accuracy in a torque wrench is important, consistancy from one use to the next is just as important (more important in the long run). Keep in mind that the accuracy of a torque wrench is thrown into a cocked hat in practical terms by the fastener to fastener variation in friction coefficient, even in fasteners from the same manufacturer's lot. While this spread can be reduced slightly by proper tightening techniques (part of the bottom of the more or less bell shaped curve of values gets folded into the middle; the top percentage doesn't change), here is what happens when you test the ACTUAL preload applied to a fastener by applying a specific torque: in tests using a torque selected to give a preload in pounds equal to 67% of yield of the fastener, the ACTUAL final preload varies between 40% of yield and 90% of yield in a statistically valid sample with a target of 67% of yield!! If you tighten each fastener in the group in an alternating pattern (in the case of two action screws, simply alternate between the two) in three increments, about 1/3, 2/3 and full torque (or 4 increments, about 1/4, 1/2, 3/4 and full torque; using more than 4 steps doesn't seem to gain anything), then do check passes (after waiting at least 2 minutes from when final torque was applied) at full torque until no motion occurs, you will raise the floor of this range so that it is well above 40%, but the top won't go up any. Those who design bolted joints are aware of this behavior and the joint designs deal with it adequately, but the bottom line is that one doesn't need to obcess over the choice of a torque wrench (just stay away from junkers or obviously abused specimens, and check the calibration once in awhile), as it's accuracy will be moot compared to what fastener to fastener preload variation due to varying friction considerations do to the actual (as opposed to target) preload.
How to avoid this? Eliminate friction as a significant factor by using angular turn instead of a torque wrench. There are other solutions, but they are economically beyond the the scope of the hobbiest like ourselves.
All the above can be safetly ignored, it's just a long winded way of saying don't waste a lot of money going after a torque wrench rated at better than 2% accuracy when you can get a slightly less accurate one for a whole bunch less - it's practical accuracy will be about the same, because of the friction variation among fasteners. And a little bit of time spent playing with angular turn can yield astonishing consistancy with little or no $ investment.
While accuracy in a torque wrench is important, consistancy from one use to the next is just as important (more important in the long run). Keep in mind that the accuracy of a torque wrench is thrown into a cocked hat in practical terms by the fastener to fastener variation in friction coefficient, even in fasteners from the same manufacturer's lot. While this spread can be reduced slightly by proper tightening techniques (part of the bottom of the more or less bell shaped curve of values gets folded into the middle; the top percentage doesn't change), here is what happens when you test the ACTUAL preload applied to a fastener by applying a specific torque: in tests using a torque selected to give a preload in pounds equal to 67% of yield of the fastener, the ACTUAL final preload varies between 40% of yield and 90% of yield in a statistically valid sample with a target of 67% of yield!! If you tighten each fastener in the group in an alternating pattern (in the case of two action screws, simply alternate between the two) in three increments, about 1/3, 2/3 and full torque (or 4 increments, about 1/4, 1/2, 3/4 and full torque; using more than 4 steps doesn't seem to gain anything), then do check passes (after waiting at least 2 minutes from when final torque was applied) at full torque until no motion occurs, you will raise the floor of this range so that it is well above 40%, but the top won't go up any. Those who design bolted joints are aware of this behavior and the joint designs deal with it adequately, but the bottom line is that one doesn't need to obcess over the choice of a torque wrench (just stay away from junkers or obviously abused specimens, and check the calibration once in awhile), as it's accuracy will be moot compared to what fastener to fastener preload variation due to varying friction considerations do to the actual (as opposed to target) preload.
How to avoid this? Eliminate friction as a significant factor by using angular turn instead of a torque wrench. There are other solutions, but they are economically beyond the the scope of the hobbiest like ourselves.
All the above can be safetly ignored, it's just a long winded way of saying don't waste a lot of money going after a torque wrench rated at better than 2% accuracy when you can get a slightly less accurate one for a whole bunch less - it's practical accuracy will be about the same, because of the friction variation among fasteners. And a little bit of time spent playing with angular turn can yield astonishing consistancy with little or no $ investment.
Lapua40X said:
This is the same one I bought. Its heavy duty and doesnt flex or bend. It functions solidly and is accurate. Its a lot better product than I was expecting for $50. A torque driver is a MUST if you are working on firearms and accessories. If your not using the proper tool for the job then you could easily damage your firearms and accessories!
One thing to keep in mind is that ANY lubrication on the threads changes the torque value required.There are a number of sources that list the REDUCTION % in accordance with the lube applied. Some are shocking....40% reduction with certain moly lubes. Naturally in our uses on firearms the size of fasteners are quite small, however ARP( if any one makes better hardware I don't know them) has an excellent free catalog that is full of valuable info regarding torque and lubes .
I've read some comments about torque wrenches and loctite not being needed. I do NOT agree with that at all. I might as add an armorer on fighter aircraft we were required to use loctite AND safety wire. It would be a safe guess on my part the US military has some strong feelings about securing fasteners.....they tend to be very particular with their aircraft.
Outrider nailed it down nicely regarding consistency and torquing patterns/ procedures.
http://beta.arp-bolts.com/?src=bolts
I've read some comments about torque wrenches and loctite not being needed. I do NOT agree with that at all. I might as add an armorer on fighter aircraft we were required to use loctite AND safety wire. It would be a safe guess on my part the US military has some strong feelings about securing fasteners.....they tend to be very particular with their aircraft.
Outrider nailed it down nicely regarding consistency and torquing patterns/ procedures.
http://beta.arp-bolts.com/?src=bolts
M-61 said:
+1 on torque wrenches and Loctite. While high initial preload and minimization of fastener to fastener preload variation (within the limits set by the fastener materials used and the joint design) are the core of a solid joint, using a torque wrench does not mean you can skip the Loctite where it is required.
An interesting sidelight on lubricationg fasteners; if you have a specified dry torque for assembling the joint, you can use gun oil, motor oil or any automotive or similar grease not laced with graphite or molybdenum disulfide and not change the torque. The pressure additives in these lubricants (including those fortified with teflon) are Not the same ones needed at the very high specific pressure loadings encountered in the flank engagement of threads and the bearing surface of the screw or nut, so once you get beyond basic snug-down of the fastener prior to using the torque wrench or angular turn, they don't change the friction coefficient. For that, you need lubes that are generally billed as "anti-sieze" compounds, which contain ground up microfine graphite or MoS2 and usually some metallic ground up microfine element (usually aluminum, copper, zinc or, before the EPA got on their case, lead) in an oil or light grease carrier, and a 40% reduction in a dry torque, as pointed out by M-61, is definitely a must with MoS2 based thread lubes.
My employer of many years, before I retired, allowed me to spend about a quarter of a million dollars on friction coefficient tests with specific thread lubes and material combinations over about a 10 year period, and one thing we discovered is that when testing actual preload for a given torque input, when the fasteners were dry or lubed with oil or grease, the surface finish of the fastener was more important than the use of oil as opposed to dry threads. In one series of tests we did dry threads and steel fasteners with steel nuts, then several months later we duplicated the test, but with fasteners from a different lot (in this case, a different manufacturer also; both were quality products), lubricated with oil. The calculated mean friction coefficient resulting from these tests was actually very slightly HIGHER for the fasteners lubricated with oil than for the fasteners tightened dry in the previous test with a different lot of fasteners!
A quick procedural note: when you lubricate fasteners prior to installation, both the threads and the bearing face of the fastener (the face going against the clamped material) or the face of the clamped material should be lubed. So going into a tapped hole, hit up the bearing face of the head of the screw as well as the threads, or in a through bolted joint, lube the screw/bolt threads and the bearing face of the nut.
Dang this is getting technical!
This IS a very good thread.
When I mount a set of bases on a rifle for somebody, they are completely amazed that I don't have a bottle of loctite handy. Then they REALLY raise their eyebrows when I put lube on the threads of shoulder/face of the fasteners.
They ask why? My response, if the fastener is not doing it's job, you need a different fastener material or a larger fastener.
When I mount a set of bases on a rifle for somebody, they are completely amazed that I don't have a bottle of loctite handy. Then they REALLY raise their eyebrows when I put lube on the threads of shoulder/face of the fasteners.
They ask why? My response, if the fastener is not doing it's job, you need a different fastener material or a larger fastener.
I worked on the MGH Proton Therapy project at General Atomics. The installation incorporated several 35' diameter steel space frames that would carry 250,000 pounds of magnets to steer the beam line. We devoted little engineering analysis to structural strength after initial verification. The bulk of analysis effort went to bolted flange interfaces and resultant deflection. A lengthy procedure was written to specify the preparation, sequence and torque values for over six hundred large fasteners per space frame. There is much more to tightening a fastener than most realize.
Steve, do you think the Borka wrench is good? Like OP I am wanting one for my action screws and scope rings
So if manufacturer says 50 in/lbs on action screws then that is what I would set the tool for and it snaps over correct?
So if manufacturer says 50 in/lbs on action screws then that is what I would set the tool for and it snaps over correct?
[br]savageshooter86 said:
Andrew, [br]
That's exactly how it works. The design is pretty clever in that it snaps over at two different values, depending upon which side is used. Different values within the range are determined by using holes spaced along the length, changing the leverage and torque value. Mine has 15, 18, 21, 24, 27 and 30 on one side and 36, 43, 50, 57, 65, and 72 along the other. Covers a good range and is very compact. The last was a big point for me in that I already carry too much crap around.
I really like my wheeler ! wheeler gunsmith set is good also , for the money !
Are you referring to scope rings and mounts? Then the 10-65 lbs.in. is fine. Generally the rule of thumb used to be to get one that's middle of the range covered what you would be using. (That's OLD info and it might have changed.) e.g. You want to torque many fasteners to 10 inch pounds. Then the one with the range of 10-65 would NOT be the best choice. Today there are electronic wrenches and I have no idea if they fall under these guidelines.
TAJ45
Silver $$ Contributor
I have to agree even if I am the OP..........this has been enlightening indeed.
However, from the dim, dark recesses of what once used to be my mind, it seems that 65 in lbs won't cover the actions........and another poster said he tore up the intrawebs looking for torque specs and came up dry.........so, even if I get my hot little hands on one of some stripe, I'll be at a loss as to action specs.
I do thank everyone for your thoughts, opinions and founded facts.
I LIKE good information. Tom
So, next question = What do I torque action screws to?
However, from the dim, dark recesses of what once used to be my mind, it seems that 65 in lbs won't cover the actions........and another poster said he tore up the intrawebs looking for torque specs and came up dry.........so, even if I get my hot little hands on one of some stripe, I'll be at a loss as to action specs.
I do thank everyone for your thoughts, opinions and founded facts.
I LIKE good information. Tom
So, next question = What do I torque action screws to?
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