Enlarge 3/4" Holdfast Holes to 1"

Posted on 30 September 2016

There are a variety of inexpensive and quick ways to enlarge 3/4” holes on your benchtop to 1” (or any other dimension). One of the simplest is to use a 3/4” dowel and a 1” spade bit, a technique I first saw on the Benchcrafted blog.

In a nutshell, you saw a kerf down the dead center of the dowel to create a channel for the spade bit. I used an inexpensive 1” Ryobi spade bit from the home center and found it created a perfect slip fit with a thin-kerf (3/32” wide) table saw blade.

Then you epoxy the spade bit into the dowel, ensuring it’s perfectly centered in the kerf. After the glue cures, you have a custom stepped-drill bit.

Insert the dowel into your 3/4” hole. Run the drill up to full speed before starting the cut. This will greatly reduce any splintering of your benchtop. Drill about 3” into the benchtop and remove the bit and dowel. Finish the hole with a 1” auger bit.

The Benchcrafted method works perfectly. My only caveat is that you should chose a high-strength, slow-setting epoxy that is heat-resistant. I used a typical 5-minute epoxy. After 10 holes, the epoxy failed.

That left me with two 3/4” holes on my benchtop that needed to be opened up to 1”. Next week I’ll demonstrate a different method for enlarging those holes.

— Christopher Schwarz

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  • Andrew Cover: January 30, 2018

    Just glue a 3/4" dowel about 1/2" long into the existing hole and let it cure then use your 1" forstner bit centered into the 3/4" dowel and once you get started, it will guide itself.

  • Hans Deseure: December 27, 2016

    “Next week I’ll demonstrate a different method for enlarging those holes.”
    Did I miss that ?

  • Nordichomey: October 05, 2016

    I thought you holdfast price was high. I looked at other ‘like’ products and your price is actually really hood. Thank you! For someone on a tight budget a Gramacy is a good solid product alternative in a lower price range.

  • Graham: October 04, 2016

    I have no experience with a holdfast like these but do recall from Roubo’s drawings that the holdfast is slanted at quite an angle in the top of the bench. Did you experiment with that?

  • Kermit Perlmutter: September 30, 2016

    I have done the same job by screwing the lead screw of an auger bit into the center of a section of dowel. Use a softwood dowel, check that it is a loose enough fit to the existing hole and pilot drill for the screw. Worked a treat, and all that exercise will remind me to double check bit size before drilling.

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