Troubleshooting Holdfast Issues
by Patrick Harper - Blood, Sweat, and Sawdust
After boring the first few holdfast holes, I realized that I had serious issues. My holdfasts simply weren’t biting. Often, they were jumping around in their holes. I had to find a solution, and fast.
The bench top is 4-1/2 inches thick. The holdfast holes are 3/4 inch in diameter. I am using Gramercy holdfasts. They are very well made, and should survive years of abuse. I did some research and determined that the most likely cause was the thickness of the bench top. How could I resolve this with the holes already bored?
I received some excellent advice from my friends on Twitter and decided that I would counter bore the holes from the bottom with a large diameter hole. To center the holes, I inserted a piece of 3/4 inch dowel. After some trial and error, I determined that the most effective nominal thickness was around 3 inches. The holdfasts work beautifully. The solution was quick and easy.
I need to clean up the surfaces and coat everything in boiled linseed oil. Then, I will finally be able to start my first project on the Roubo. Stay tuned
You can find links to my other Roubo posts here: Project Index
Blood, Sweat, and Sawdust 
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I lightly sanded my Grammercy holdfast shafts with 150. It made a big difference.
Drew, I was going to try that as well. As it stands, they hold pretty well. It seems as though they are getting better with use.
I have heard that problem before. Same solution. My top is 3 3/4 so I think I will be ok. I did pick up two hold fasts from Tools For Working Wood at HandWorks. I have to decide where I am going to put holes in my top.
Bartee, mine are all about 3-1/2 from
the back and 15″ apart. Seems to work well for a 21-1/2 wide top.
Do your holdfast holes go all the way through the benchtop? From the description of your problem and solution it almost seems as if they are not all the way through.
Yes, the holes go all the way through. However, the counterbore from the bottom only goes partially through.