Holdfasts and MDF?

[Danny Thompson]

Anyone had luck with Holdfasts in MDF?

On a recent trip to TFWW, I picked up a couple of no-longer-pending-patent Gramercy holdfasts. Funny think is, I don't have a real woodworker's workbench.

Both of my workbenches are topped with formica on an MDF substrate. One is 1 1/2" MDF, the other is 1/2" MDF with 2x4 ribs.

The options I have considered are drilling dog-holes in the 1 1/2", in the 1/2" through a 2x4 rib (on edge), adding some sort of reinforcement below the mdf, or replacing a section of mdf with solid wood (rather not do this).

Will the holdfasts hold in either of these?
Is reinforcement needed? What kind.
How thick a material is needed for the holdfasts to grip securely?

Other advice?

[David Gendron]

I think that they would probably hold... but for how long? I think the MDF would distord and breack down! I think the best thing to do, would be to cut a 2" strip out of your bench top and replace it with a piece of 2x3 or 2x4 hard wood that you would have driled 3/4" holes in it! the top of my bench is DF and the holes have distored a little bit...
David

[Adam Cherubini]

Anyone had luck with Holdfasts in MDF?
Both of my workbenches are topped with formica on an MDF substrate. One is 1 1/2" MDF, the other is 1/2" MDF with 2x4 ribs.
Other advice?

No experience with MDF and holdfasts. But thinking, the formica may be a problem or a solution. The contact area for a hold fast is top and bottom. The pressure from the hf may crack the formica. I'd be inclined to countersink the formica away. You may find that a brass bushing is an easy solution to a buggered hole in these sorts of benches. You may even be able to get a special drill with a nose on it to pilot on the hole to open it up.

Or it might be time to pick up a copy of Schwarz' Workbench book and build yourself a proper woodworking bench.

Adam

[glenn bradley]

I'm thinking that due to how they work they will slowly mutilate your dog holes. I went with these (http://www.sawmillcreek.org/attachment.php?attachmentid=95319&d=1219465348). Quick to make, won't eat your MDF top and cheap (http://www.sawmillcreek.org/attachment.php?attachmentid=95321&d=1219465362).

[Jim Koepke]

Just by the way it works, a hold fast is going to distort a hole.

Sometimes I use a bar clamp. The stop pin is knocked out of the bar and then the grip end can be taken off. They have to be held when they are off the bar or all the pieces can go flying.

My bench came with a screw type hold fast that sits in one of two holes that have a liner made of what looks like inch and a half conduit.

For smaller stuff, I like the Veritas Surface clamps. Pricey, but worth it. I have two, wish I had bought four when I had more income.

jim

[Tri Hoang]

You find that after using it a few times, the dog holes will chip at the edge (top)...another while and the holes become loose. Maybe it's a sign that you should build a real wookworker's bench http://www.sawmillcreek.org/images/icons/icon10.gif.

[David Keller NC]

"or replacing a section of mdf with solid wood (rather not do this)."

This suggestion isn't quite as radical as replacing a whole section of your bench with solid wood (that'd probably be more work than it's worth - just glue up a whole solid wood top). What you could do is to drill a 1-1/2" hole with a forstner bit, then insert a 1-1/2" face-grain plug of maple or similar hard wood. You can make these by laminating a couple of maple boards face-to-face to give you the required thickness, then cut out the plugs with a hole saw. The hole saw will leave a hole in the center of the plug, but since you've got to drill a 3/4" hole through it anyway for the holdfast, that doesn't matter.

The only real difficulty here is that you may have trouble finding a forstner bit/hole saw combination that will give you a tight plug. If you've a friend with a lathe, that's another option for creating the requisite face-grain plug.

[Danny Thompson]

Great suggestions guys. Thanks. I actually own a copy of and have read Chris's Workbench book. Enjoyed it very much. I just don't think I'm ready yet. I haven't settled on a design.

So, do they make brass bushings especially for dogholes?

The other clamp options are interesting but I already have the holdfasts and would like to use them. I think the answer may lie in the strip option.

Hmmm. . .

[Eric Brown]

You could buy large diameter hardwood dowel (1 1/2 - 2")and insert into same sized holes on your bench. If holes already there, use a jig to align the bit. Drill, glue the dowel into the holes and then redrill the dog holes.
Use a countersink gently on the dog holes and the dogs will go in easier.

Good luck. Eric