MFT and clamps?

[Woody Knotsensplintahs]

Hi,
Dues to my shop space requirements I store my full size yet to be used sheets of plywood on the top of my old heavy duty workbench, and then I lay a piece of full size sacrificial board on top of the stack for use as a work surface.
I want to use a full size piece of MDF set up with a MFT grid, but due to the height of my setup I would like to continue to lay this work surface flat upon the bench as I have in the past. In other words, I would rather not add a riser grid to support the MFT, and provide clearance for access to the underside of the MFT.
I am hoping that I may be able to find some hold down clamps that do not require space under the MFT, and can somehow grip the 3/4" thick MDF to accomplish my goal.

Do you know of any such hold down clamps?

Thank you!

 

[nclemmons]

I have this one and it's a great clamp for placement and securing from above the surface.

Not cheap but a really nice clamp if you don't want to reach under the table.
http://www.leevalley.com/us/wood/page.aspx?p=57059&cat=1,41637

 

[Woody Knotsensplintahs]

Hi,
Thanks for the suggestion. I had seen that clamp and it seemed like a good idea that might not be so good in practice, so it's good to think that you like it.

Do you think it stresses the sides of the holes in way that may make them less precise?

Thank you.

 

[nclemmons]

Woody -

Not at all.  It holds pieces quite well and I've used it for several years with no apparent hole deflection or damage.

I just noticed they only seem to have the 3/4" version now.  I have a 20mm version.

Another choice that I like - https://www.axminster.co.uk/axminster-trade-clamps-ratchet-hold-down-clamp-103566
This one does require under-table access, but it too is nice because it's held in place for rapid clamping and stock removal with one hand.

 

[Woody Knotsensplintahs]

Thank you again for the helpful info.

Switching gears, Can someone explain how much room is required beneath the bottom of the MFT surface to use a bent rod style clamp such as those that are available from Festool, Bessey, etc.?

I am asking so that I may understand how much increase in height I would have to provide if I choose to go with a cheaper clamping solution than the Veritas clamp mentioned in the last few posts.

Thank you.

 

[Dick Mahany]

I just noticed they only seem to have the 3/4" version now.  I have a 20mm version.

I was just looking at a 20mm version in the new Lee Valley catalog and have been considering purchasing one [link]

 

[Cheese]

I built an 80/20 frame and then inserted a MFT top. Because the 80/20 extrusion surrounds the perimeter I find these Bessey clamps pretty useful as they can be placed anywhere.

[attachimg=1]

Here it's shown clamping a round dog down just to point out its versatility.  [smile]

[attachimg=2]

However Bessey does make an adaptor to use this clamp with the MFT 20 mm holes.
https://www.bessey.de/en-US/BESSEY-...-adjust-toggle-clamps/Horizontal-toggle-clamp,-flanged-base
https://www.bessey.de/en-US/BESSEY-...s/Auto-adjust-toggle-clamps/Workbench-adapter

 

[Woody Knotsensplintahs]

Hi,

Thank you for the suggestion. I do have a few work surfaces with T track which I use with various clamps including the Bessey style that you have pointed out, but for the MFT table, which I am currently trying to set up, I am prioritizing its role as sacrificial backing to prevent tear out so I do not want any metallic materials which might interfere with a track saw blade. 

This looks like a useful device which can be used from the top of the MFT table and could be used with the Bessey style clamps you have mentoned:

I would still like to learn how much room I will need underneath the table to insert this style of clamp into the MFT holes:

I wonder if a couple inches will be enough. I do not want to make enough room to allow for reaching underneath with my arm in an effort to attach a fastener to the bottom of some accessory, but a adding a couple of inches is a possibility.

Thank you.

 

[Roachmill]

However much space you leave underneath, make sure it's enough to allow you to fish out whatever drops through a hole. It will happen!

 

[Dick Mahany]

I wonder if a couple inches will be enough. I do not want to make enough room to allow for reaching underneath with my arm in an effort to attach a fastener to the bottom of some accessory, but a adding a couple of inches is a possibility.

Thank you.

[member=70323]Woody Knotsensplintahs[/member], the tip of the clamp protrudes 55mm from the bottom of a 3/4" thick top as shown below, however as the clamp is rotated to the 90 degree position, it looks to be 57-58mm at the max swing of the arc from what I measured.

[attachimg=1]

 

[Woody Knotsensplintahs]

Thank you very much for the helpful information!

Thank you.

 

[GoingMyWay]

I normally rest a 2' x 4' piece of MDF that has 20mm holes drilled in it on top of  bench dogs on my Kreg Mobile Project Center.  The Kreg bench dogs elevate the MDF up about 1/2".  That's not enough to get a clamp under without physically lifting up one side of the MDF (no problem in my case since it's only 2' x 4' and not screwed down).

I just took some measurements and it looks like you'll need at least 2" of clearance to get the clamp under.  1 1/2" was not enough.

[attachimg=1]

[attachimg=2]

[attachimg=3]

[attachimg=4]

[attachimg=5]

[attachimg=6]

 

[Woody Knotsensplintahs]

Thank you for the detailed information!

Thank you.

 

[GoingMyWay]

No problem!

I'm not sure what you call it - maybe the throat?  but that part on both the Quick Clamp and the Screw Clamp is the same size.

[attachimg=1]

[attachimg=2]

I wasn't sure so I thought I'd compare them.

 

[veric13]

2" is accurate for the clearance needed.  I had to put 2" as the gap on my assembly table that has holes (mft style) for the clamps to work.