.. He had never heard of drilling a clearance hole with a twist drill along the inside of the hole circumferance.. What a differance that makes!
I've never heard of this trick either. So can you explain more about this? How many holes - to many and the whole plug falls out and then you have no center hole for the guide bit.
For a one inch hole saw I use a 3/8 inch drill, 2 holes about 180 apart. The biggest twist drill that you have that will not weaken the middle just makes it go faster.. As far as weakening the hole center, I never really worried about that because once the saw is in and cutting the the skirt of the hole saw keeps it going straight (at least that is what I want to beleave
). I scar the hole (just start it) so the OD of the hole is well defined. Then sink the twist drill holes so they cut into the hole saw kerf, if it doesn't matter I go OD to OD, that way the teeth of the holesaw pass right over the clearance hole, this gives the best chip clearance. A handy air hose to blast at the saw helps keep the clearance holes clean too.. If it does matter I ease up and have the twist drill just hit the ID of the hole saw scar..
Hope this helps! The Old Man taught me this as a nipper and I thought it was a standard shop trick, glad to pass it along!
