How to Drill & Ream a Holdfast Hole

Posted on 21 September 2016


One of the reasons the Crucible Iron Holdfast works so well is there is a close fit between its untapered shaft and its hole in the workbench top. To get this tight fit, we think you need to drill each hole in your workbench and then gently ream it out a bit to get a nice, close fit.

It takes about two minutes per hole. But the results are worth it.

To bore and ream the hole, we recommend the WoodOwl 1”/25mm auger bit. These are the best auger bits we have encountered, and they work well in electric drills and braces.

The WoodOwl bit is metric, so it is slightly undersized compared to the shaft of the holdfast, which is approximately .970” +/-. So the holdfast will not fit in a freshly bored hole until you ream it out a bit.

You ream the hole by spinning the bit (we use a corded drill), while plunging the bit in and out of the hole while providing sideways pressure. After your first hole you will become an expert.

Drill and Ream Holdfast Holes from Christopher Schwarz on Vimeo.


The above video shows the process from start to finish using a WoodOwl bit and a simple jig that keeps your bit plumb. You can download plans for the jig and full instructions for the holdfast here.

— Christopher Schwarz

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  • Christopher Schwarz: September 22, 2016

    We’ll be posting a similar tutorial to this in the next week. But this is the best way.

  • Gary Warner: September 22, 2016

    How do you recommend redrilling 3/4" holes to 1" holes. Glue in a dowel and then redrill?

  • Derrick: September 22, 2016

    Any suggestion on enlarging 3/4" holes if we want to move up to this size holdfast?

  • Derrick: September 22, 2016

    That lump hammer in the video is nice. Any information on the source, or perhaps is this a future Crucible offering?

  • Thomas: September 22, 2016

    Any advice for cleanly increasing 3/4" holes to 1"?

  • Erik: September 22, 2016

    Just a caution for those eager beavers ready to bore into your benches, the Amazon link for the wood owl bit ships in 1 -2 months. They are in stock here:

  • Christopher Schwarz: September 22, 2016


    I’d probably keep the same pattern of holes because there are times when clamping in an end vise is not the right choice, such as when dealing with thin materials or when sticking mouldings on narrow stock.

  • Martin : September 21, 2016

    Would you recommend the same amount of holes for a bench with an end vise, or possibly leave some out or maybe even change the pattern? The ones maybe interfering with the actual vise mechanism excluded of course.

    Best regards


  • Christopher Schwarz: September 21, 2016

    Normally dog holes and holdfast holes are different things. (Check the blog entry on where to locate holdfast holes.)

    However we recommend wooden dogs that you make yourself. They are much friendlier to your plane soles.

  • Michael: September 21, 2016

    What bench dog do you recommend for a 1" hole (mine are 3/4).

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