This is a follow up to something I had posted about a while back: welding in a hole and re drilling and threading it.
I had decided that next time I would over drill the hole before I welded it back in. Well, the hole had already been oversized from an M4 to M5 and the threads were wallowed out, and I wanted to get back to the original fastener.
The hole was already oversize, the part was 5 mil thick mild steel. I used a copper flat bar between the part and the bench, and migged the hole shut. This time, I did NOT quench it! While it was still toasty, I ground the weld flat, and let it air cool from there. A badly abused transfer punch gave me center with the cap plate set in place. The tap index was missing the drills, so I eyeballed a drill laying about, and drilled it nice and slow using the end mill as a drill press; the vice on the drill press is junk. No problem drilling through the weld. The tap was a little tougher, and more than once I questioned the wisdom of not having miked the drill. But it was a nice spiral. The tap, and I went slow, no problems. The cap plate I left with oversized holes, it's not critical, and a couple washers under the fasteners will make it all good.
To sum up, the oversized holes seemed to make it go easier.
