The Ford Barn - View Single Post

johnneilson · 03-02-2022, 12:03 PM

Katy,

you are right, the thread form is 60 deg, what the theory is that a 20 pitch is less inclined angle in rotation. Sorry, not buying that either.

FWIW, helicoils are not stronger than the base metal, IMHO, only used for thread repair if necessary. Timeserts are much stronger due to the solid form unlike a wire, which can roll.

Part of the mystery about bolt torque is when you get close to the yield strength of the fastener. I have had grade 8 7/16-20 bolts yield at 45 ft# torque. the quality is just not there sometimes. Now, get into higher grade fasteners such as rod bolts, same 7/16-20 and designed for clamping you do not torque, you measure the amount of stretch overall. BTW, it is approx 70 ft# torque.

John

03-02-2022, 12:03 PM	#14
johnneilson Senior Member Join Date: Jun 2010 Location: 34.22 N 118.36 W Posts: 1,060	Re: Flywheel bolt torque Katy, you are right, the thread form is 60 deg, what the theory is that a 20 pitch is less inclined angle in rotation. Sorry, not buying that either. FWIW, helicoils are not stronger than the base metal, IMHO, only used for thread repair if necessary. Timeserts are much stronger due to the solid form unlike a wire, which can roll. Part of the mystery about bolt torque is when you get close to the yield strength of the fastener. I have had grade 8 7/16-20 bolts yield at 45 ft# torque. the quality is just not there sometimes. Now, get into higher grade fasteners such as rod bolts, same 7/16-20 and designed for clamping you do not torque, you measure the amount of stretch overall. BTW, it is approx 70 ft# torque. John __________________ As Carroll Smith wrote; All Failures are Human in Origin.