TriggerTech screw sheared off

[cb175]

Had the front screw on my TriggerTech shear off on my Ibex today.

The damage to the thread was caused by removing it with ViseGrips.

Pretty sure it wasn't loose - just sheared off.

Has anyone else had this happen?

Still had the screws from the original Excal trigger so replaced with one of them.

[BrotherRon]

can you post a picture of the ens of the screw where they are broke off?
If it is a fresh break it takes a bit of pressure to do that???

[cb175]

It is a clean, new break. I had shot 4 arrows and then could not cock the bow as the trigger housing had risen up above the rail.

[Deerstalker]

I believe that if the trigger housing rotated up when the front screw broke that some damage may have occurred to the rear screw. Did you check that out when you replaced the front screw. The TT instructions state that new supplied screws with lockwashers are to be used when installing the TT trigger and I don't see the lockwasher in your pictures. Were they used?

http://www.triggertech.com/instructions.html

[Seafermiles]

Appears that it was a torque shear. May have been done during assembly and only just a tiny bit left to break off. You should be OK just replacing the bolt.

[racking up points]

Appears that it was a torque shear. May have been done during assembly and only just a tiny bit left to break off. You should be OK just replacing the bolt.

Yes, but that trigger box would have stripped before you could ever apply that amount of force; I don't think you could shear the screw before stripping the hole in the bottom of the trigger box.

If you read the TT installation instructions and watch the videos they explicitly state not to over-tighten the trigger box fasteners, they are just supposed to be snug. I am assuming the OP followed those directions.

This seems like maybe you had a faulty fastener, stranger things have happened.

[newbie]

Appears that it was a torque shear. May have been done during assembly and only just a tiny bit left to break off. You should be OK just replacing the bolt.

Yes, but that trigger box would have stripped before you could ever apply that amount of force; I don't think you could shear the screw before stripping the hole in the bottom of the trigger box.

If you read the TT installation instructions and watch the videos they explicitly state not to over-tighten the trigger box fasteners, they are just supposed to be snug. I am assuming the OP followed those directions.

This seems like maybe you had a faulty fastener, stranger things have happened.

I wonder if a loose fastener would cause this, excess movement and stress?

[coolhl]

I wonder where the screws were manufactured?
Does anyone really trust anything made in China 100%
Norm

[Boo]

Appears that it was a torque shear. May have been done during assembly and only just a tiny bit left to break off. You should be OK just replacing the bolt.

Yes, but that trigger box would have stripped before you could ever apply that amount of force; I don't think you could shear the screw before stripping the hole in the bottom of the trigger box.

If you read the TT installation instructions and watch the videos they explicitly state not to over-tighten the trigger box fasteners, they are just supposed to be snug. I am assuming the OP followed those directions.

This seems like maybe you had a faulty fastener, stranger things have happened.

I wonder if a loose fastener would cause this, excess movement and stress?

I think this is most likely the case. If the only screw holding is the front, then when fully cocked, the fastener will be bend forward by the limbs. On the shot, that fastener will take a back and forth bending.
A fastener that is over tightened will show twisting which this one does not.
We'll never know 100%, we can only guess.

[racking up points]

One more reason to buy titanium fasteners, I guess.

[Normous]

One more reason to buy titanium fasteners, I guess.

X2, can't wait.

[Species8472]

One more reason to buy titanium fasteners, I guess.

Commercial grade titanium has 30% less tensile strength than grade 5 steel bolts and 50-60% less than grade 8 steel bolts. Unless you are using an exotic titanium alloy (some of these are on par with grade 8 steel or even slightly exceed) your best choice for strength is still common grade 8 steel bolts.

The primary advantages of titanium are superior corrosion resistance and lighter weight (about half way between aluminum and steel) they only real strength advantage it has is when you compare it aluminum (about 2x the tensile strength).

[Normous]

One more reason to buy titanium fasteners, I guess.

Commercial grade titanium has 30% less tensile strength than grade 5 steel bolts and 50-60% less than grade 8 steel bolts. Unless you are using an exotic titanium alloy (some of these are on par with grade 8 steel or even slightly exceed) your best choice for strength is still common grade 8 steel bolts.

The primary advantages of titanium are superior corrosion resistance and lighter weight (about half way between aluminum and steel) they only real strength advantage it has is when you compare it aluminum (about 2x the tensile strength).

Ti64 uses Grade 5 titanium which is equivalent to a grade 8 SAE steel fastener.

[foofoo]

from my searchin around Black Oxide steel scews can be grade 5 or grade 8.Titanium can be grade 2 or grade 5. i found some negative reviews on some titanium screws coming out of China prone to shearing.id wanna know how you can be sure what the proper grade your getting.ive never had an issue with any Excalibur bolts shearing.only heads stripping but i bet its more the allen wrench than the screw head.

[racking up points]

i found some negative reviews on some titanium screws coming out of China prone to shearing.id wanna know how you can be sure what the proper grade your getting.

[/quote]
Ti64 uses Grade 5 titanium which is equivalent to a grade 8 SAE steel fastener.[/quote]

What Norm and I were referring to was Ti64, an American manufacturer that is making Ti fastener kits for Excalibur bows. Check out their website if you need technical info.