BoltScience website

[Deleted]

Amongst the highly erudite stuff on their website there a couple of interesting pages.

In www.boltscience.com/pages/vibloose.htm they effectively say that spring or plain washers are worse than useless.

In www.boltscience.com/pages/strength.htm they say "Studies have shown that for threaded assemblies of usual proportions, tap-drill size is relatively unimportant so long as the percentage of thread height is greater than 60%. Tapping costs are likely to be lower if the lowest possible thread height is used."

My method of selecting a tapping drill, for 1/4" or larger, is to find the largest drill that will pass through a nut of the relevant thread and to take the next 1/64 larger - I won't feel so guilty about that in the future

[alanstepney]

For model engineering work, around 75% thread engagement is about right.
Tubal Cain wrote an excellent article in ME on this subject, giving the maths for various threads, and that formed the basis for the tables in his books.
Charts showing the "low engagement" tapping sizes can be found at, www.alanstepney.info/page8.html

[steamjohn248]

I used to do quite oa bit of "subbing" for a firm involved in producing automotive assembly robotics. The gaffer always advised me to use a size bigger than the tables (working in metric i.e. 0.1mm) to avoid grief with broken taps in stainless and MS. Good enough for the motor industry then!