Festool MFT ratchet clamp question

[Zach Dickason]

I cannot find this answer anywhere, hopefully you guys can help. I am planning to build a heavy, overbuilt, Paulk style workbench. I would like to know how thick can the top be and the Festool clamps will still be able to thread into the 3/4 holes. For what I'm planning it would be great to use a double layer of 3/4 for the top. I'm not sure if the 90* bend in the clamps can make the turn through 1.5" of plywood though.

[Jim Dwight]

Zach, I use one layer of 3/4 on my paulk style workbench and it works well. I do not have any Festool clamps but the Grizzly clamps I use are not super easy to get through. I doubt they or Festool would go through a 1.5 inch top.

These tools are also meant for 20mm holes, not 3/4. For clamps it probably doesn't matter much but bench dogs and Festool quick acting horizontal clamps depend on the 20mm size holes. I think Kreg stuff is for 3/4 holes, however.

[Dick Mahany]

The Festool clamps will handle a 3/4" top thickness, perhaps a tiny bit more for 20mm holes. I don't think 7/8" or thicker will work and I'm not sure if they will even work in a 3/4" diameter hole. EDIT 5/20/20: I just tried it and the clamps will indeed fit through a 3/4" diameter hole in a 3/4" top.

The clamps have a very tight radius on the ends.

I believe some folks have made thicker tops and relieved the underside of the holes with a large chamfer however I don't have direct experience in doing that.

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If you have the clamps, you could determine it empirically by gluing a few scraps together or using a piece of 2x4. Drill the 3/4" or 20mm hole through it. Then insert the clamp and determine where the interference is and enlarge as needed.

[Steve Fish]

FWIW, my top is 3/4 ply plus 1/4 hard board on top. I used a round over bit in a trim router on the bottom. I would not go any thicker.

[Curt Putnam]

I have a little Sjobergs bench with a 1.125" thick top. The Festool clamp will not go through the 3/4" dog holes.

[Zach Dickason]

This is exactly why I came. Thanks for the responses folks. I had initially thought of adding a chamfer to the underside. Not sure I'm liking that idea now considering the size it would have to be. Back to the drawing board.

[Tom Henderson2]

I concur with Dick Mahany.

The Festool clamps need to be opened all the way, and then inclined until almost touching the table surface), before they will fit into the 30mm holes in my MFT top as shown in Dick M's excellent photos.

And as Dick shows, it is the tight radius bend that is the issue, not the length

So if you want to use Festool clamps with a thicker top, you'll need to counterbore the underside of the holes.

[Paul F Franklin]

If you really want the thicker top, you could consider alternate clamps, like the lee valley veritas surface clamp. They are available for 20mm and 3/4 I believe. More expensive than the festool quick clamps but they are really nice clamps (didn't think I'd ever use the phase: "more expensive than the festool......!)

[Mark Carlson]

I watched Mike Farrington on youtube make a 1in thick top with 20mm holes. The festool clamps wouldn't make it through so he added a slight chamfer to the underside of the holes. So no way would a 1 1/2 thick top work.

[Jim Becker]

Yes, a combination of 20mm holes with clamping slots provides the ultimate in flexibility for clamping and using 20mm dog hardware. But it's true that pushing beyond 19mm thickness will be an issue for some accessories.

[Jim Dwight]

Zach, I don't think you need more than 3/4 thickness if you put in the inner structure Paulk uses. His are designed for 1/2 plywood and he shows himself walking on them in one of the videos. I think mine with a 3/4 top and bottom are plenty sturdy. MFTs are MDF which is much weaker than plywood.

[Zach Dickason]

Thanks for the responses. It probably might have helped if I had explained my plan. I currently have a traditional Nicholson bench with a large twin screw vise and holdfasts. I built it when I had dreams of using hand tools only. I am drifting away from that dream and really enjoying using more power tools in my work. I also have a large torsion box assembly table that is dead flat on the top with 90° sides. Both of these tables take up way to much space together (Nicholson 8'x2' ,assembly 6'x4'). I am planning to build a bench that combines both. I need it 8'x4', dead flat, 90° sides, heavy enough for planing, and rigid enough for hand tool work. Even though I'm using more power tools I still employ hand tools about 30-40% of the time. I'm really liking the Armor Tool line of bench dog clamps. They have a few variations, none of which need threaded into the hole (they just drop straight in like a holdfast).
I would just build a massive 8'x4' torsion table with a grid of dog holes for the clamps however dust and shavings will routinely be falling into the holes so I thought an open paulk style table would possibly be a better option so I can vacuum it out on occasion. Obviously it wouldn't sit on sawhorses but rather a heavy and thick base. Also, I don't need a full blown MFT grid of precise holes as I won't be needing to break down sheet goods on this thing, I don't even own a track saw. I'll probably just space all the holes around 5" apart or so. Ill figure that out later.
Sorry for the long post. What do you think about this plan?