Sunday, November 4, 2018

Things That I Did Not Know

When you drill and tap a hole, you are supposed to slightly countersink it.  This provides a funnel that directs the screw or bolt into the first threads.  I can really feel the difference in getting them started.


  1. Just a little breaking the edge at the entrance to the threaded holes. Bean counters take it out of fabrication instructions and the result is lost time and some times even damaged threads during final assembly. But I will attest that after awhile you forget you are even doing it when you make such a hole (it becomes automatic as a final action in fab).

  2. If you examine machine screws and bolts, you will see they have a complimentary bevel at the tip. One or the other helps, but having both makes a big difference.

    There are engineering specs for the end of threaded hardware. Ditto for the hole start, although the details are generally simpler, IIRC. Lonngg time since I've seen a print for these.