Re: Entry Step Rivets
Reply #8 –
80% of thread is quite "iffy" when hand tapping a 1/4-20 thread. The 1/4-20 tap web or cross section is inadequate for the force required to turn the tap. Unless extreme caution (and I do mean EXTREME) the tap will break.
A 1/4-28 tap will require less force to turn due to the shallower thread form. But because there are more threads per inch the holding force is greater. In most metals when 55% or more of the thread form is present and 1.5 times the thread dia of thread length the fastener will break befor the threads will fail.