Lessons Learned: Boring Holes

Sun Apr 28 2024

#woodworking

I’m installing a face vice in my workbench. This requires boring some holes through the aprons of my bench, through the jaw blank I made to allow the vice to pass through.

It went badly and I’m quite depressed about it.

I bought some forstner drill bits since that seems to be the internet’s consensus on boring smooth holes. Since I don’t have a drill press, I also got a drill guide, hoping that would help ensure straight and square holes.

I finished drilling through the jaw blank. It took longer than I thought and required quite a bit of downward pressure on the drill to get the bits to catch. Initially, I hadn’t read any instructions on forstner bits and I was running it way too fast. My bench is softwood which helps but even then the ideal speed for a forstner bit is much slower than for a twist bit. e.g. ~1000 RPM, depending on the size of the bit (bigger bits -> slower RPMs). This is due to heat dulling the bit blades.

My hand drill is variable speed but I have no idea how fast it’s going so I just have to eye ball it. I know from reading the labels on it the top speed is ~2900 RPM so I adjust based on that. The other thing to watch out for is that at lower speeds the drill motor can heat up. Frequent stops to cool down motor and bits is recommended.

Next, I lined up the jaw with the apron and transferred the hole center to the apron and continued drilling from there. Foolishly, I didn’t check the hole centers were where I expected them to be. Turns out I drilled quite a bit out-of-square through my 3 inch jaw which led to at least one of the holes being somewhere between 1/8 and 1/4 inch higher than I expected. Ugh.

Unfortunately I think I placed too much faith in the drill guide. The amount of pressure I had to use to get the forstner bits to catch meant the guide wasn’t doing it’s job.

For next time

  • Drill slowly - check the recommended max RPM on the drill bit. Remove frequently to let it cool down.
  • Always check your expected layouts when transferring holes or marks.
  • Try drilling slower, at least at first, to let the drill guide be stable.
  • Probably better off drilling through scrap, ensuring that’s square, then using that as a guide, rather than the drill guide.