Building a Clamping Table

      A woodworker considers the idea of making his own pneumatic clamping table. October 19, 2013

Question (WOODWEB Member) :
Like everyone else, I have been using pipe clamps, long bar clamps, etc. for years/decades to position, hold, and glue frame or box products, and currently, shutters – principally rail and stile frames. As an efficiency method it would be beneficial to build a simplified form of a clamping table such as sold by Kreg, using pneumatic clamping air cylinders instead of loose clamps with limited-travel hand cranking, etc. Interest is in two rails clamped between two side stiles – just two clamps applying pressure on the two sides.

In looking at cylinders, I see incrementally increasing diameters, references to flow controllers, foot switches of several varieties – forward backward, continuous, non-continuous…

What about working air volume requirements? Control of speed of piston advance? I would like ability to slowly advance piston making sure that tenons/dowels are properly positioned before smashing them; what about determination of final pressure?

What options are desirable, and what is the best source? I prefer a low profile, less-than pretty, commercial source versus store front retailer with consumer marketing and equally fancy markups.

I am looking for guidance in proper sizing – avoiding the simplistic bigger is better syndrome. I particularly invite the mechanical engineer-types among us to spring forth with advice on part selection for such a simple, small table setup.

Forum Responses
(Architectural Woodworking Forum)
From contributor D:
You need diameter for pressure. That said, my case clamp only uses 2 3" diameter cylinders per joint. With the regulator set at 40psi, that's only about 600 lbs clamping force.

Speed control is easily done with a flow control valve. No fancy electronics required. If you put the flow control on the outlet of the cylinder you can easily add a valve that bypasses the flow control to give you a full speed option.

Good suppliers are Festo and SMC.

From contributor J:
I bought a Ritter clamp table with pneumatic clamps rather than buy a bunch of long bar clamps. The clamping table has the advantage of being a square reference and since it is an easel style it takes up much less space than a large flat table.

The pneumatic clamps from Ritter are around $400 each new but they work well and are fairly easy to repair. You can find used Ritter clamp tables for good prices. There is one listed on this site for $950 that would be a good deal if it is big enough for your needs. I paid $2000 for a 5' x 8.5' Ritter with 8 clamps and have been very happy with the space savings and utility.

From the original questioner:
Thank you - I had considered tables but footprint is an issue, e.g. the Kreg, but had overlooked the used market. The pneumatic component approach is out of my field of expertise, and will consider some form of table, working in collaboration with another forumite.

From contributor D:
I haven't done this because I bought a case clamp, but it is possible to use heavy truck brake chambers as pneumatic cylinders. Cheap, long lasting, spring return. Can't ask for much more.

From contributor V

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A 3" cylinder at 40 psi only gives 282 lbs force. How much would be in a Uhling case clamp? I think they have 5" bladders, so that would mean 785 per clamp at 40 psi.

From contributor D:
You hit the nail. Excuse my ignorance but what kind of pressure are we looking at as provided by an average bar clamp hand pressure for a base line comparison?

From contributor V

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I actually have no idea about that! Maybe 300 tops? Just a guess.

From the original questioner:
Given the scale and complexity of these methods I am going to try a third choice - modified screw clamping. But using 1" x 20" threaded crank as used on cabinetmaker/wood vises (see Grizzly P/N H5577). Combined with some angle iron, it should allow a reasonable two sided frame on a table or leg frame support.

Above all, I now have a proper perspective of the scale, complexity and relative costs involved in my original question. Thanks everyone.

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