Scope Mounting Screw Torque
This is a hot topic today. I will give you what I have learned over the past 30 years of doing this for a living. It is not all that hard, the screws need to be tightened, not over tightened, enough so the mount is not loose and the screws will not loosen up. I do use thread lock on ALL scope mount and ring screws. I use small screw, service removable thread locker. It is generally pink or a milky red or purple in color. Please see my Thread Locker post for more details.
Here are the most important things to remember when torquing screws.
We use screws made in the USA. Purchase only ALLEN® brand Allen wrenches. Inferior brand wrenches fit loose in the screws and will lead to rounding out the head.
When you insert the wrench into the screw head make sure it bottoms out. If you only insert the wrench in say half way, that will also lead to rounding out the head. We see screw heads rounded out and upon examination with a 20X magnifying glass it is obvious most of the time the wrench was only inserted part way.
When torquing screws with a Torque wrench to a particular specification there are many variables. I have looked over at lest 20 torque specification charts and even most of them don’t agree on specs. There are also different specifications for dry or lubricated screws. For our purposes we are going to consider the thread locker on the screw to be a lubricant. Here are the specs we suggest using.
6-32 9 inch pounds
6-40 11 inch pounds
6-48 13 inch pounds
8-32 18 inch pounds
8-36 20 inch pounds
8-40 22 inch pounds
I know this can all be debated until the cows come home but you can’t go to far wrong using the above specifications. I suggest checking the torque after your first trip to the range. If you have done everything correctly all the screws should be set at the same torque you originally applied.
Many of you know I am an old timer. I have been using the following method of tightening scope mount screws since I started in business. I can say I have never had a failure using this method.
Using a short arm ALLEN® wrench I snug the screws down. We all know what snug is. I use one finger at the tip of the wrench and tighten it lightly. I then turn the wrench another 1/8 of a turn. We did an experiment at the shop and found that is pretty consistently 20 inch pounds of torque with me doing it. I am sure it varies with different people tightening the screws but it should get you pretty close.
All in all I don’t believe it is anything to get uptight about. It is pretty straight forward. Torque wrenches are great and provide consistency but I don’t believe you can’t mount a scope mount without one. It has been being done for over 100 year without Torque wrenches with great success.