Festool Clamping Elements / Metric Question

[Brian Dormer]

Does anyone know what size screws (or bolts) fit the threads in the Festool Clamping Elements?

I need longer bolts so I can use the Clamping Elements on my workbench (1.75 inches thick - a good deal more than an MFT).

My calipers seem to say it's 1.5mm - but I don't know enough about metric hardware to be sure.

TIA-

[Dave Falkenstein]

My caliper says about 7.75 mm, which translates to a metric bolt size of M8, I think. However, I NEVER use the bolt/knobs on the bottom of the Clamping Elements. They fit tightly into the holes in the MFT and the knobs are not needed, IMHO. If your workbench has holes drilled to fit the Clamping Elements (20mm?), you can likely get away without using any bolts. If you want bolts that fit, you could take one of the Clamping Elements to Ace and look in their metric section.

[Brian Dormer]

Dave,

Thanks for responding.

I'm building my bench (just taking a momentary shop break) right now... The whole "dog hole question" is still unresolved.

I've temporarily borrowed a set of clamping elements.

I've tried two different 20mm bits for boring holes. One from Rockler, one from MLCS. The Rockler bit left holes that were a tad too big for the Clamping Elements - quite wiggly. The MLCS bit was pretty close to the snug fit in an MFT. I have also learned that a B&D Workmate (even my "original" 1960's pre-metric-system Workmate that I inherited from my Uncle) fits the clamping elements post quite nicely.

BUT - in every test I have conducted - I've found that without the knobs, when I clamp down on a workpiece, it will lift up quite a bit on the clamp end if the Clamping Element isn't screwed down. Which is what lead to my question. Maybe I need to go back and try that on an MFT?

Because of the workmates fitting so well, I'm beginning to suspect that 25/32 holes (.006 inches smaller than 20mm) might be the answer - but I don't have a bit that size. McMaster-Carr has one - for 32 bucks -OR- I could buy an Expansion Bit (Adjustable Spade bit) for a few bucks less. OR - I could file down a 7/16 spade bit. I'm going to have about 60 dog holes altogether (slabs, aprons and the end vise chop) - so I need "production line" type tooling or this will take forever.

What I'm considering is screwing a long wooden post onto the Clamping Element Clamps (similar to the long post on a Wonder Dog) - to add some mechanical leverage and take out that tendency to lift up.

It's a shame Festool doesn't document these dimensions - it would make this so much easier.

bd

[Dave Falkenstein]

You can get lots of expert advise on Festool by asking your question at the Festool Owners Group (FOG). Google "Festool Owners Group" to find it. The holes in the MFT are definately 20mm. The diameter of the Clamping Element is slightly less than 20 mm.

I have read about making holes in home-made benches using a plunge router instead of a drill. You would need to anchor a drill to get a hole that is both true and square - very hard to do. A drill press obviously solves that problem, but I cannot imagine using a drill press to drill a workbench top. There are some threads at the FOG about shop-made MFT's and benches.

I use the Clamping Elements frequently on my MFT and never use the knobs to secure them. Must be the accuracy of the holes in the MFT that is the difference.

If you use a router, Festool sells a 20 mm straight bit with an 8 mm shaft, if that helps:

http://www.festoolusa.com/ProductDet...ID=490971&ID=4

[Brian Dormer]

FYI -

I've been thru 3 different 20mm bits (Rockler, MLCS and Festool) - that's close to $80 worth of bits (Festool ain't cheap). NONE of the 20mm bits make holes that will hold the Clamping Elements tight to the deck when you ratchet down the clamp. The clamp lifts up about 1/16 to 1/8 depending on what bit made the hole. MLCS was the best and Festool was the worst (I know - it's blasphemy - but it's also the truth).

For reference - I bought my Clamping Elements in February 2008.

THE BEST size bit I've located is a 25/32" wood boring bit from McMaster-Carr. The holes are pretty tight for the clamping elements - but there is NO lift up when you clamp. Thats what I'll be using to drill dog holes in my workbench. I would prefer a plunge router - but just try to find a 25/32" router bit!

I suspect (but can't prove) that Festool has not only changed the size of the holes in the MFT (this has been reported elsewhere) - but has ALSO changed the diameter of the "leg" on the Clamping Elements (they are SMALLER than they used to be).

SO - if you are making a bench, jig or fixture and intend to use Festool clamps, etc. - You really need to make a couple test runs to make sure you've got the right size holes. Caveat Emptor and all that.

[Cary Swoveland]

Brian,

Are you sure you're not putting the cart before the horse? [As an aside, I once attended a presentation where the speaker used that expression, but got mixed up and had had the horse before the cart. So I always make sure I've got it right.]

As I understand, the only reason for having 20mm holes is to be able to use the Festool clamping elements. You still can't use any of the Festool hold-down clamps, because your bench is too thick.

The clamping elements are handy, but there are substitutes. Moreover, all the hold-down clamps and bench dogs made for a 3/4" hole are going to be a little sloppy in a 20mm hole. If you stick with 3/4" you can drill them with a 3/4" plunge bit (as deep as you can go), followed by most any kind of 3/4" drill bit (twist, brad-point, space, Forester).

That brings me to a question: why hasn't someone come out with cam clamps similar to the clamping elements but for 3/4" holes?

Cary