"Jean"Hello,
I found one screw on german webshop and i will replace my with it until I get a new one from my dealer from Holland.
It is M3x8 and 12,9 the last number is very important it is very very strong and durable.
Eine M3 Schraube in 12.9 hält z.B. min. 614 kg Zugfestigkeit aus!
it stands 614 kg tensile strenght.
The original screw from FX is most likely 12.9 quality as well.
Unless they have really searched the fastner market for someting of lower quality.
I think it would be alot more difficult to find a lower quality set screws in Sweden or Western Europe.
So most likely they used a standard set screw that has 12,9 quality because the are most common.
Its only when they are silver color you might suspect lower strength, if it is electro zink plated. Then it goes down in strength because of the
hydrogen brittle effect from the surface treatment. Normally it wil then be sold as 8,8.
This is why high yield screws are always black or without surface treatment
12.9 means tensile strengt is 1200mpa and yeild is 90% of tensile.
So the max stress in a M3 would be 1200*0,9*1,3²*3,14 = 5731N . Sher is approx 75% of this = 4300N (437kg)
The force on the pellet probe would be for .30 (if the pressure goes to 150bar)
15*3,14*(7,62/2)² = 683N
683N load vs 4300N set screw strenght
The problem is not the static strength of the set screw. The threads and crack initiations is probably the problem.
And the reason why one should never use threaded screws or similar to bend or take shear force.
Pins are uset for that.
If threaded coils where used to make suspensions springs for cars.
It doesnt matter if the thickness of the coil is the same, or if the material is super tough.
The springs would brake after only days.
Some reservation about everything above. I dont know exactly how the pellet probe works, or how the set screw is mounted.
Have never taken it apart.
With this said, I still love the FX guns nad everything about them. Better to lead the development and take some risks.
Nobody remembers a coward