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Screw torques for a HW97k

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KarlH63

Member
Oct 27, 2016
6
3
Texas, United States
I have two of these now. One in .177 and a second in .20. I just received the .20 last Thursday and find that the two screws at the forearm and both at the trigger guard loosen frequently. I have never had to tighten any screws on the .177.

On the .20, I've tightened the front screws to 12 in-lbs, the front trigger guard screw to 15 in-lbs, and the rear trigger guard screw to 12 in-lbs. After 75 pellets or so, I have a POI and then have to tighten again. I am not using a thread locker at present.

I did email Weihrauch and asked about the recommended torques, but haven't heard from them.


 
Thank you for the reply. I did hear from Weihrauch today and they specified 2.5 to 3.0 NM for all four screws. I think that equates to 22 and 27 inch-lbs respectively. I tightened the front two and rearmost trigger guard screw to 20 in-lbs and the front trigger guard screw to 27 in-lbs. I am afraid to go beyond 30 in-lbs as it seems awfully tight even at 27. I will try as is without any thread locker, but should they continue to loosen, that will be the next step.
 
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Here are the stock tightening specs for HW springers per HW in Germany..........
Front stock screws = 2.5 Nm is equal approximately to 22.1 in-lb, and Large trigger guard screw = 5 Nm is equal to 44.3 in-lb, and rear trigger guard screw = 2.5 Nm is equal approximately to 22.1 in-lb.

Convert newton meters to inch pounds:
http://www.convertunits.com/from/newton+meters/to/inch+pounds

I personally never put more than 15 in/lbs torque on the small 4mm rear trigger guard screw but I do use the other torque values.

One of the issues with excess HW stock screw torque is the possibility of crushing the stock wood fibers which allows the wood to compress under springer recoil. This compression allows the stock screws to "become loose" even if "thread locker" is used and the screws themselves never loosen.

I personally "steel posted" all my HW stock mounting screw holes so there is metal to metal contact after tightening so expanding/contracting stock wood doesn't affect the screw tightness.............
z0pARoAl.jpg


Here are my front stock screw cups with pilot that goes all the way through the stock forearm sides........
G4znrw4l.jpg

UTKu4Vsl.jpg

mvh5tuzl.jpg


Pics showing the installed stock mounting screws.........
PmXQtlwl.jpg

PiHBsRzl.jpg
 
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I don't know how the "aftermarket cups" are installed but I cut mine for a press fit in the stock c-bore and screw hole, then use a stock mounting screw to pull the cup into place. If the stock screw is too short I start seating the cups with a longer screw and finish up with the factory screw. For my HW springers the front stock mounting screws are M5 thread with a 0.8mm pitch.
 
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