I am about to plunge 6" three eighths dia. coach screws into one and a half inch thick 'red pine' endgrain. The thread profile is aggressive and thick, So far, my best advice to date is - "Drill a long thinnish hole and keep trying it , if it jams, widen the hole until it goes in. You'll soon get the right fit by trial and error.....", OR - "Measure the diameter of the core of the threaded section and drill that diameter hole, but no larger." (obviously). I'd have thought that a certain amount of compression was essential to get a really firm bite without splitting the wood - I favour the idea of drilling out that part occupied by the shank a bit undersize, and the thread a bit under the core diameter. These will secure cross beams to the legs of my new workbench so there'll be a lot of angular stresses.
Wise thoughts please,
Thanks,
R
Wise thoughts please,
Thanks,
R