Sundodger
WKR
Couple things
When designing a joint, that has a weaker material for the threaded portion, typically you increase the number of threads. That is done by drilling and tapping/rolling threads deeper as well as a tighter thread pitch. The general design goal is that you want that bolt to fail before the threads (not always possible and sometimes not desirable, but it's a general rule of thumb). There are lots of rules of thumb 1D vs 1.5D, vs 2D for various materials, want to see an industry fail? Look up early Ford mod motor spark plug threading. IIRC they had like 1D for AL threads, and now they are known for shooting spark plugs into the hood.
Never forget about fastener stiffness/elongation. The elongation of the fastener is a key in keeping joints together, it needs to "absorb" the in service forces and still have enough tension to keep it all together. Graph tension with respect to elongation and you want something that changes tension slowly when elongation is changed. You generally don't want the tension to fall off a cliff when the length is changed.
Diameter to length ratio (D/L) and the tensile strength of the fastener, it plays a profound roll in joint relaxation, what type of process you can use (straight tq, tq plus angle, tq to yield), and to a lesser extent (unless you go totally off the rails) sensitivity of the tq/tension relationship.
Don't take this as a nock on high tensile strength bolts, I am very pro high tensile strength bolts, it drives me nuts more companies are not using better fasters (Please use more Stainless alloys like 300 series and 450). But don't forget thread and under head forces, under head impressions and gauling is bad, you often need to downsize high strength fasteners make careful selection of coatings and under head materials to allow them to be used properly. I know this is blasphemy for RS, but even lubing threads and underhead and moving away from Loctite. I don't want to derail this thread, but for many joints lube is far superior and often necessary over Loctite.
I have actually applauded the firearm industry for using small diameter, fine pitched fasteners. Swapping a short fine thread #6 or #8 for a 1/4-20 or 1/4-28 would be a disaster from an install tq sensitivity and joint relaxation perspective. But a good point is brought up, bigger bolts that can handle the forces, but come loose from relaxation ends up being a similar failure mode to small fastener that doesn't relax as much but residual tensile loads are exceeded during service. I have always argued the answer is more numbers of smaller fine pitch fasteners.
Hopefully @Unknown Munitions is is thinking about this when they are making their new tikka clone action. They could easily make expoxying rails to the top of the action, Loctite, etc. a thing of the past with some intelligent joint design that could even be backwards compatible.
When designing a joint, that has a weaker material for the threaded portion, typically you increase the number of threads. That is done by drilling and tapping/rolling threads deeper as well as a tighter thread pitch. The general design goal is that you want that bolt to fail before the threads (not always possible and sometimes not desirable, but it's a general rule of thumb). There are lots of rules of thumb 1D vs 1.5D, vs 2D for various materials, want to see an industry fail? Look up early Ford mod motor spark plug threading. IIRC they had like 1D for AL threads, and now they are known for shooting spark plugs into the hood.
Never forget about fastener stiffness/elongation. The elongation of the fastener is a key in keeping joints together, it needs to "absorb" the in service forces and still have enough tension to keep it all together. Graph tension with respect to elongation and you want something that changes tension slowly when elongation is changed. You generally don't want the tension to fall off a cliff when the length is changed.
Diameter to length ratio (D/L) and the tensile strength of the fastener, it plays a profound roll in joint relaxation, what type of process you can use (straight tq, tq plus angle, tq to yield), and to a lesser extent (unless you go totally off the rails) sensitivity of the tq/tension relationship.
Don't take this as a nock on high tensile strength bolts, I am very pro high tensile strength bolts, it drives me nuts more companies are not using better fasters (Please use more Stainless alloys like 300 series and 450). But don't forget thread and under head forces, under head impressions and gauling is bad, you often need to downsize high strength fasteners make careful selection of coatings and under head materials to allow them to be used properly. I know this is blasphemy for RS, but even lubing threads and underhead and moving away from Loctite. I don't want to derail this thread, but for many joints lube is far superior and often necessary over Loctite.
I have actually applauded the firearm industry for using small diameter, fine pitched fasteners. Swapping a short fine thread #6 or #8 for a 1/4-20 or 1/4-28 would be a disaster from an install tq sensitivity and joint relaxation perspective. But a good point is brought up, bigger bolts that can handle the forces, but come loose from relaxation ends up being a similar failure mode to small fastener that doesn't relax as much but residual tensile loads are exceeded during service. I have always argued the answer is more numbers of smaller fine pitch fasteners.
Hopefully @Unknown Munitions is is thinking about this when they are making their new tikka clone action. They could easily make expoxying rails to the top of the action, Loctite, etc. a thing of the past with some intelligent joint design that could even be backwards compatible.
