Tikka slam fire PSA

[mxgsfmdpx]

The only time the larger M6 screw for the trigger main assembly has ever come loose is when the trigger has been modified. It won’t come loose if it’s not dicked around with.

Last I remember, 8 newton meters was the spec for that M6 screw which is somewhere around 70 inch lbs.

 

[Marbles]

The only time the larger M6 screw for the trigger main assembly has ever come loose is when the trigger has been modified. It won’t come loose if it’s not dicked around with.

Last I remember, 8 newton meters was the spec for that M6 screw which is somewhere around 70 inch lbs.

Mine are at 80 in.lbs. (about 9 Nm) with thread locker.

The Sako trigger screw I just grabbed is a property class 12.9, so torquing to 18 Nm (159 in.lbs.) would be within its working spec.

I'll go dig out a Tikka screw. --> also class 12.9.

 

[mxgsfmdpx]

Mine are at 80 in.lbs. (about 9 Nm) with thread locker.

The Sako trigger screw I just grabbed is a property class 12.9, so torquing to 18 Nm (159 in.lbs.) would be within its working spec.

I'll go dig out a Tikka screw. --> also class 12.9.

I’ve tightened multiple of them well past 80” lbs as well with no issues so far.

 

[fraz01]

Has anyone ever measured how much it takes to break torque on a factory installed screw? Do they recommend replacing the screw if it's removed?

 

[SloppyJ]

First time ive seen this and its good to know. Just more reason not to dick around with the trigger other than backing off the adjustment.

Certainly not an isolated Tikka issue. I have a 1960s Model 100 where the trigger was loose and it wouldn't let the bolt come back. Had to carefully break the stock to get it fixed. Sucks when there's a live .243 round stuck in there.

Just more reason to go through your rifles in entirety.

 

[Marbles]

Has anyone ever measured how much it takes to break torque on a factory installed screw?

I have not, but it is tight and requires some force to break free.

Do they recommend replacing the screw if it's removed?

Not that I'm aware of any recommendations and would not replace them routinely.

My reasoning (before learning this I still wasn't replacing them): As a property class 12.9 fastener it is not being torqued anything close to yield.

A grade 8 (SAE rating and what us in the US tend to use) is equivalent to a property class 10.9 (ISO rating used for metric). 12.9 is the strongest grade. I would not be surprised if my stainless actions would strip before the fastener, or the aluminum trigger housing would crush. The 416R stainless only has a upper end tensile strength of 110,000 psi while property class 12.9 fasteners minimum tensile strength is 176,900 psi. In an M6 bolt this translates to an absolute tensile load just north of 5,500 pounds.

7075 aluminum has a tensile strength of up to 86,000 psi, compressive modulus should be slightly higher.

Somebody should go torque that bolt until something gives and come back and report.....

Tikka went for overkill on that bolt because they know it is critical. The wingnut behind the wrench is my concern.

 

[mxgsfmdpx]

Has anyone ever measured how much it takes to break torque on a factory installed screw?

Yes. Around 65-70” lbs.