Fatigue in spring washers

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NTSOG

Member
Jun 15, 2017
88
1
Victoria, Australia
G'day,

​This is for those who are trained in metalurgy or are skilled in metal work. I have two Weihrauch rifles from 1980/'90 that are very accurate when all bolts and screws are tightened to exact specifications. They are an HW 80 [.177] and a Beeman [Theoben] RX [.20]. It's taken me quite some time [being inexperienced] to get them tuned, but I am now getting good groups. The one issue I have is that in both rifles the pivot bolt is coming loose from the action of cocking. Consequently accuracy decreases. Weihrauch rifles have a strong spring washer under the round-head 'bolt' on the right side. Is it possible that over time this washer can lose its 'holding' effect due to fatigue. [I assume that the purpose of any spring or lock washer is to 'lock' a bolt and nut so the combination cannot become loose?] I don't mind having to tighten the bolt every so-often, but would like to lock it permanently.

Any advice would be appreciated.

Jim

via Ballarat
​Australia.
 
I imagine it would be possible those washers no longer apply sufficient force after a long service life, in the case of these service washers I'm not sure what could be a long service life, perhaps sending an email of to Weirauch would be prudent.
​Beyond replacing the I would be certain there was sufficient lube inside the pivot point of the breach block and between it, shim washers and the forks so it doesn't grab hold of the bolt as it rotates while cocking. Also be certain to de-grease/oil the bolt threads and the cap.

​How often are you having to tighten the forks? Once per tin?
 
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Hi Cachoze,

​What you say about lubrication makes sense. Degreasing the bolt thread at the end is a little harder, but clearly must be done. The bolt itself is threaded in part and keeping those threads clean seems impossible to me. I am having to tighten both rifles about every 100 pellets or so. It may pay to replace the washer regardless. I do wonder just how much the natural wear that comes from age comes into the problem? I don't mind so much that I have to tighten the bolts as long as I am getting tight groups.

Thank you,

​Jim.
 
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