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Striped out threads in FX no limit Rings

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eodman

eodman

Member
Dec 29, 2017
182
11
Cal, United States
I started to install the scope on my new Crown MK2 and found that there was almost no clearance between the scope objective bell and the barrel about 10 thou. When I went to install the magazine I found the scope was to low. I had to raise the scope rings 55 thou to allow the mag to clear with a little extra clearance and when I went to tighten the screw I had to really tighten the screw with some force to pinch the ring tight enough to hold the ring in place. I used a short Allen Wrench and slowly tightened the screw trying not to over stress the screw. Well just when I was able to stop the movement in the ring the screw striped out the threads. 

Upon inspection I found that the screws only engage the threads about halfway need to have a longer screw. I wanted to shoot the gun so I drilled out the threads and installed Metric Helicoils in both rings and reinstalled the rings. So be careful and go slow. I'm an old man and didn't know I had that kind of strength. 


 
I got this little puppy to prevent any accidents. Goes from 10.5-26.5 inch lbs.

1.2-3nm

20201202_201021.1606968705.jpg

 
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I didn't strip the upper ring screws I striped the big screw that allows the ring to be moved up or down. You need ft pounds not inch pounds to tighten the ring upper body to the lower part of the ring assembly. these are the FX no limit Rings not the standard rings. I have installed thousands of rings in my business over a period of 40 years with out a problem.

The problem is the 5mm screws are a little to short and don't engage enough of the threads for the torque required to hold the two part ring base together and keep from moving. These are not the small ring strap screws these are large 5mm base screws. Sorry about the confusion.
 
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It takes a lot more than 30 inch pounds to pinch the lower part of the base to hold the upper from moving.
Click to expand...

Do you think it's an isolated incident dealing with manufacturing defect specific to your stripped screws or do you believe all are like that? I would address FX USA to let them know about it either way. It's the first time hearing about it with this brand of scope rings.
 
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eodman - "I started to install the scope on my new Crown MK2 and found that there was almost no clearance between the scope objective bell and the barrel about .10 thou. When I went to install the magazine I found the scope was to low. I had to raise the scope rings .55 thou".

Holy cow! .10 thou - that's really small! How were you measuring it ".10" thou is . 0001 inches and ".55" thou is .00055 inches.

BTW - I have 4 sets of these rings and never had a problem with any of them.
 
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smithfan4152 - You are correct on both counts. However, (unless someone changed out the screw) these mounts have (at the loosest), nearly 2 times the thread depth vs screw diameter. Although it is a fine thread the inside of the threads has been hard anodized. I tighten these screws really tight as I don't want them to move (vertically) and never had a screw strip out.

I will say that I know a few people who cannot tighten a screw or bolt without stripping the treads.😩
 
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I always use antisieze on the screws so I don't gall the threads. I have 6 air rifles with FX no limit rings and these are the only ones that failed. I inspected the other rings and found that the screws were longer. Also I took some apart and found that slots in bottom part of the bad ring was a littel wider than the the other ones. So my conclusion is that I got a ring that was out of spec. I got three Crown rifles that were bad so I figure that one ring set is about the norm for me. I will let FX USA know but I did fix the rings and they are working just fine.

My only reason for the post was to let others know to be careful. I do appreciate most of your input some were a little nasty but hey whatever floats your boat. There are are a great bunch of people here and the exchange of info is wonderful and intertaing. I still love my FX Rifles.
 
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I'll just offer a couple of observations. I have three sets of FX no limit rings. The adjusting screw on all of them tightens sufficiently with less than 30 in/lbs of torque. I don't often use my torque driver, I guess after turning thousands of these things I've developed a good feel. But, I do have a good, made-in-USA torque driver, which I just used to test a couple of these things, and 20 in/lbs worked on the two I tested. Also, those 5mm adjusting screws, in my rings, have about 8 revolutions of thread engagement. I have no scope on any rifle that has a screw requiring 30 in/lbs of torque. So, my guess, the OP has a couple of too-short screws, and, if 30 in/lbs of torque isn't holding the adjusting feature securely, there may be a machining error in the parts that created too much clearance, thus requiring too much torque. Just my thinking on it.
 
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anti seize will allow you to stretch a screw more with the same torque being applied, making it easier to strip a screw or the threaded bore. I only use anti seize in application where I am worried about being able to unscrew without gulling. Having used gallons of anti-seize in my life time, I do NOT use any on my airguns. Places I use anti-seize are in high heat or corrosive enviroments, that include wet/rust forming areas need anti-seize

most of what I know is learned by screwing up

thread engagement a problem that has a solution, this is a quick google cut and paste 👇

What is the minimum thread engagement?

It is commonly known that the minimum recommended thread engagement to make a strong connection for a component with a tapped hole is approximately 1 times the nominal diameter in steel and 2 times the nominal diameter in aluminum. In many cases, (tapped hole in a softer material, special alloys, etc.)Mar 19, 2015
 
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