I recently bought a scope rail whose mounting instructions suggested 20 - 25 inch pounds of torque plus 45 degrees of rotation. That last piece confuses me as I have never heard that before.
Gunsmithing TORQUE INSTRUCTIONS
- Thread starter EM92wx
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It's fairly common in the auto industry. Easiest way without a torque wrench set for *'s is to mark the screw at 12 o clock and turn to 13:30. 1/8 turn. Hope this helps.
20-25 in. lbs. is typically the max range for most picatinny bases I've seen. This is what I use and have never had one come loose.
I don't understand why they would give you this range, then say go an additional 45 degrees. Typically with angle of torque, you initially just "snug" the bolt down until their is contact, then tighten to the specified angle.
I don't understand why they would give you this range, then say go an additional 45 degrees. Typically with angle of torque, you initially just "snug" the bolt down until their is contact, then tighten to the specified angle.
Maybe this is a choice between one or the other. Since I have a Borja Torque Wrench I’ll use the specified inch pounds. Thank you for the responses.
Usually the torque on the rings to the rail is like 45-60 depending. 20-25 is usually what the torque is on the ring caps.
If the instructions state 20-20 inch lbs + 45* then do both. Be sure to use tapered screws as well (self centering).
It's called torque to yield. Very common in the automotive and equipment industry. If you ever remove that base, the screws or bolts will need to be replaced. Clamping force is generated by bolt stretch.
Torque to angle isn't always torque to yield. It all depends if the screw is stretched into its plastic deformation state, or if it's still elastic.
A torque to yield spec will usually be defined by a TTY designation. If the screws need to be replaced after every use, the manual will state that, and I would agree they are indeed TTY.
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TNX for the replies. Very interesting. The rail is from Near Manufacturing in Canada specifically for the Sako TRG-22. A really excellent piece of work.
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Please forgive me as I am not a mechanic, and have only used torque wrenches as stated... Do these instructions mean the you torque to 20-25 inch pounds, then tighten the screw/bolt an additional 45 degrees so it gets stretched and becomes a one time use screw/bolt?
This.
size and types heavily dictate torque values.
I’m guessing it’s a torque value or a rotation value.
not both.
Deutz Diesel have TTY bolts and you do both but they’re designed for it with a stretch undercut area.
Judging buy the instructions in the OP, it's torque, then 45 degrees. He doesn't mention however, whether the manual states the screws are one time use however.
