Got a torque wrench and was SHOCKED

[Cowboybebop]

I've mounted plenty of scopes in my 10+ years in this hobby and have always used the L wrench that comes in the ring package, usually a T-15 torx variety. I have read plenty of articles about how easy it is to apply too much torque, which crushes the scope tube, strips out threads, etc. So I was always very aware of how much torque I put on my equipment.

My technique has always been to go as tight as possible using the "short end" of the L wrench, then switch to the "long end" and go another quarter turn. Most of the internet forums, including this one, advocate this advice when a torque wrench is not available. I found that using this technique my rings were extremely "snug". And I very rarely had any issues with rings coming loose.

Fast forward to last week. I got a CDI (made by Snap-on) torque wrench as a gift and began checking my rifle scope rings and mounts. I was shocked!

All of my 8-40 and 6-48 mount and ring bolts began to turn at the 9 inch-pound mark. Some of them SEVERAL REVOLUTIONS before settling at the require torque ratings from Leupold, which are 22 inch/lbs for 6-48 and 28 inch/pounds for 8-40.

Here I was worried about over-torque and I've only been going 9 inch/pounds! I now cannot understand how people exceed the torque rating using that little L-wrench. Seems impossible to me. Maybe I'm a weakling though.

Anyway - I thought this story might help some DIY'ers out there. Get a torque wrench and check your rings!!!

 

[stoky]

nice gift!
I have a 3/8" drive Snap-On inch-pounds wrench, but it's pretty awkward for gun stuff. I recently bought the Wheeler Fat Wrench. It comes with a nice (little) set of tips and some guidelines for gun torques.
It's worth checking mounts and bedding screw tightness once in a while, especially if accuracy issues pop up. In my case it's usually a loose nut behind the trigger though.

 

[rondog]

I've always torqued things to "two ughs and a grunt". Works for me. Kinda developed a feel over the ages for what's "enough". I do have a proper wrench for larger, more important things, like auto engines and suspensions, etc.

 

[armabill]

It's better to do it looser than tighter. You can always tighten more without problems but too tight and it's too late, the damage is done.

I tighten only with my two fingers using the small end of the allen wrench tightening each side alternately. Then just a little more with the long end.

 

[pintler]

All of my 8-40 and 6-48 mount and ring bolts began to turn at the 9 inch-pound mark. Some of them SEVERAL REVOLUTIONS before settling at the require torque ratings from Leupold, which are 22 inch/lbs for 6-48 and 28 inch/pounds for 8-40.


That sounds really odd to me. I always use a torque screwdriver on scope mounts, and torque wrenches for lots of things. There is usually a only a fraction of a turn between when the fastener head makes contact and full torque.

If we take 'several revolutions' to mean 5 turns, 5 turns of a 40 TPI thread moves the screw head an eighth of an inch. If you started with a 1/4 inch long scope screw, it would now be 3/8 inch long. It's going to break before that happens.

 

[Jenrick]

So just to check, it's an in/lb torque wrench and not a ft/lbs or netwon/meter? Those would give you dramatically higher torque for the same reading.

-Jenrick

 

[barnbwt]

All of my 8-40 and 6-48 mount and ring bolts began to turn at the 9 inch-pound mark. Some of them SEVERAL REVOLUTIONS before settling at the require torque ratings from Leupold, which are 22 inch/lbs for 6-48 and 28 inch/pounds for 8-40.


That sounds really odd to me. I always use a torque screwdriver on scope mounts, and torque wrenches for lots of things. There is usually a only a fraction of a turn between when the fastener head makes contact and full torque.

If we take 'several revolutions' to mean 5 turns, 5 turns of a 40 TPI thread moves the screw head an eighth of an inch. If you started with a 1/4 inch long scope screw, it would now be 3/8 inch long. It's going to break before that happens.

...or simply crush whatever that screw is clamping down on.

 

[Cowboybebop]

All of my 8-40 and 6-48 mount and ring bolts began to turn at the 9 inch-pound mark. Some of them SEVERAL REVOLUTIONS before settling at the require torque ratings from Leupold, which are 22 inch/lbs for 6-48 and 28 inch/pounds for 8-40.


That sounds really odd to me. I always use a torque screwdriver on scope mounts, and torque wrenches for lots of things. There is usually a only a fraction of a turn between when the fastener head makes contact and full torque.

If we take 'several revolutions' to mean 5 turns, 5 turns of a 40 TPI thread moves the screw head an eighth of an inch. If you started with a 1/4 inch long scope screw, it would now be 3/8 inch long. It's going to break before that happens.

These ones I was referring to only happened on a few, and they were all on the Leupold QRW steel rings which use 6-48 screws. Also at most we are talking about 1.5 full turns, not 5. That would be insane. Ha.



"It's better to do it looser than tighter. You can always tighten more without problems but too tight and it's too late, the damage is done.

I tighten only with my two fingers using the small end of the allen wrench tightening each side alternately. Then just a little more with the long end."


Armabill, that's pretty much what I used to do. You should check with a torque wrench and see if my experience is typical. Maybe I have really weak hands.


And yeah, my wrench was set to inch/lbs. Foot pounds is like 12 times the force! Everything would have probably snapped in two if I had tried that.

I should also mention that all of these screws have CLP on the threads. Which according to Leupold is allowed.

 

[hq]

It's not a bad idea to lap the scope rings before installing the scope. It doesn't take much for the clamp/contact to be uneven and damage the tube at a fraction of recommended torque specifications. Think about trying to break an egg by squeezing it evenly vs. pushing your thumb through the shell.

 

[homers]

I noticed the same as the OP when I got the wheeler fat wrench. most of my mount screws were much less than the recommendations even though there were fairly well snugged tight by hand

 

[pintler]

"I noticed the same as the OP when I got..."

That's interesting. I usually grab the torque wrench or driver to be sure I don't overtorque. Maybe I've been using them so long my hands are partly calibrated

 

[.308 Norma]

All of my 8-40 and 6-48 mount and ring bolts began to turn at the 9 inch-pound mark. Some of them SEVERAL REVOLUTIONS before settling at the require torque ratings from Leupold, which are 22 inch/lbs for 6-48 and 28 inch/pounds for 8-40.

Interesting! Thanks! I'm going to get myself a little torque wrench now and check out the ring bolts on some of my rifles now.

 

[imashooter]

Thought I posted this but perhaps not. I once found a rather large (to me) difference between a ring / mount manufacturer's "ring" torque values and the scope manufacturer's scope values. The scope manufacturer suggested I should always follow the scope manufacturer ring values. Based on material, thickness, where the scope innards are located, etc. Sounds good to me so that's what I follow. Normally those values are readily available however sometimes the need arises to call / email them.

 

[RainDodger]

A torque wrench (big and little) is one of THE most valuable things to have in your shop. All my life I've had a tendency to over-tighten things, so I use the torque wrench religiously. I'm sure it has saved me a lot of $$. In my case I got a nice upper-end digital that can be switched between lb-ft, newton meters, inch/lb, etc. For the small stuff, one of the screwdriver-type inch/pound ones. Anyone who doesn't have one should do themselves a favor and fork over the $$ for one. Remember - for the torque wrenches that have springs in them (screwdriver-type, click type, beam type, etc.) either follow directions, or turn the scale to zero for storage.

One other thing to note... I have seen countless videos of guys using their wrenches incorrectly! If you attach the wrench to an extension or to a tool that has some length to it, that tool or extension MUST be at a ninety degree angle to the torque wrench in order to get an accurate torque setting on the fastener!! Think about it... if you add length, you're going to over-torque things! If you're putting on an AR barrel for instance, PUT THE BARREL WRENCH ON THE TORQUE WRENCH AT A 90 DEGREE ANGLE TO THE TORQUE WRENCH!!