On Sat, 12 Oct 2013 12:27:27 -0500, Gordon Shumway
wrote:

On Sat, 12 Oct 2013 09:27:38 -0700, scritch
wrote:

I made a workbench from some gluelams I got for free. It is quite
substantial, being about 5 inches thick; very solid. I drilled some
bench dog holes in it, and then I bought a holdfast.

Unfortunately, even though the holdfast was described as 3/4" diameter,
it's really a bit larger, and I need to enlarge the dog holes by about
1/8". I saw one technique where you grind the shoulders of a spade bit
at 60 degrees and proceed carefully down the holes to enlarge them.
Does anyone have better ideas?

I'd use a twist bit and take it slow like dpb suggested. Or if you
want to use a Forstner bit drill the desired hole size in a piece of
scrap and then clamp it to your bench to be the guide for the Forstner
bit to get it started. After you get deep enough you will no longer
need the guide and it can be discarded.

That's what I would do, even with a twist drill. The hole in the
"guide" scrap can be drilled at the same time. I'd probably use
hardboard for the guide.

Also, I initially drilled too many holes. Any thoughts on plugging
them? I might just glue in some dowels, but someone might have a more
elegant idea.

This is an easy fix! Go to Harbor Freight and get one of their
recently inventoried "Negative Kerf" drill bits. They're fantastic!!
:-)

Should have used a portable hole.

https://www.youtube.com/watch?v=dI-I8DQD4LI