Pressure Clamps

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Project by DakotaHeirlooms posted 01-09-2019 10:20 PM 1398 views 3 times favorited 5 comments Add to Favorites Watch

Whenever you’re making those really big projects such as table tops, doors, counter tops, desks, cabinets, shelving, or any other job requiring gluing two or more pieces of stock together, “double bar clamps” work great. The clamps in the following discussion apply pressure on the work piece face when edge-clamping to prevent bowing and buckling large panels

I bought 3 ShopSmith “Double Bar Clamps” and was pleased with the results. I bought the 36” clamps that measure 42” end to end.

Recognizing that a wood worker can never have too many clamps, I decided to buy more. The ShopSmith clamps are pricey, but I ran across some Wood River “4 Way Pressure Clamps” sold by Wood Craft and bought a set. All I had to do was supply the wood. The clamps worked, but were unwieldy. To increase the versatility, additional “bars” can be purchased.

Before Christmas of 2018, Rocker had a sale on their version of a “4-Way Pressure Clamp”. The sale price was right, and I bought 4 sets.

The instructions to make the wood pieces said to drill a series of 5/8” holes spaced 2” apart down the centerline of the board face of a 2×4 piece of lumber. Then rip the board lengthwise through the centers of the holes, creating two pieces approx. 1-1/2” x 1-11/16”.

I made a couple of changes: I glued up enough 13/16” Oak to make 4 clamps, and ripped and planed them to 1.5” x 3.5” x 42” strips. I drew a line down the center of each strip, and marked off 2” intervals. I set my ShopSmith to the Vertical Drill Press mode and set the fence to drill 3/16” above the centerline.

Using a 5/8” Forstner bit I drilled a hole, then flipped the strip 180” and drilled a “companion” hole. The result looked a little like a figure 8. Yon can see the effect in the photo.

Satisfied with what I had so far, I drilled all the other holes above the line, flipped the strip 180 and repeated the process. When the holes were drilled in all 4 strips, I set the table saw up and ripped each strip

When all four strips were ripped, I applied 2 coats of varnish to each, with an extra heavy coat on the “bottom” of each strip. Why? The glue I use doesn’t stick to a varnished surface, so I don’t have to worry about glue oozing out of the joint. If there was a problem, I’d use masking tape on the strips, and replace it after each use.

The following photo shows the 3 brands of clamps. From left to right:

WoodRiver: Weighs 8 pounds.

ShopSmith: Weighs 6 pounds.

Rockler: Weighs 7.6 Pounds.

The better of the 3 is probably the ShopSmith: ShopSmith says that the secret to their special dual channel clamping action is the “ingenious curved radius of each hardwood bar”. This precision cut radius distributes pressure equally over the entire width of the project. See the ShopSmith site for more details.

The WoodRiver appears to have a more robust threading than the Rocker: otherwise the hardware appears to be the same.

A little hint when using any of the clamps: Stick a couple pieces of scrap slightly bigger than the piece being clamped between the bars on each end to facilitate putting the piece between the upper/lower bars. Once the pieces are in place, remove the scraps and tighten the clamp.

-- Harry Sorenson Dakota Heirlooms

5 comments so far

View BlueRidgeDog's profile


499 posts in 284 days

#1 posted 01-09-2019 11:28 PM

Thanks for sharing. I would like to get a few sets, but I have yet to see a clamp that did not evoke that feeling.

View dannmarks's profile


1005 posts in 1086 days

#2 posted 01-10-2019 04:41 AM

I have had very good luck with this clamp.

And I have not had to worry about bow if the jointed sides were at the proper 90 degrees. The Jawhorse applies @ 2500 lbs of pressure.

View therealSteveN's profile


3846 posts in 1078 days

#3 posted 01-10-2019 12:24 PM

I worked for ShopSmith back in the 80’s. I bought several pairs of those back then. I managed to keep several, and think they are a clamp, and a caul all in one. More recently they have been re-invented somewhat due to the all metal Damstom clamps, way to spendy for me though. They have been in the limelight, and because they essentially are the same thing, the wooden ones have renewed interest.

Both types require a small amount of skill, easily learned doing some dry mock ups to gain understanding. Once you feel comfortable I would suggest doing that before the glue goes on, lest you end up with a mess. Once you know what to do, and when, it’s like riding a bike.

I agree the ShopSmith brand have always worked better than the others, at least without modifications. Price wise they are kinda spendy nowadays too. Way back when I bought mine, not so much. I think they were the lowest price accessory they sold, at least the ones that actually did something.

-- Think safe, be safe

View AM420's profile


226 posts in 888 days

#4 posted 01-10-2019 08:53 PM

I guess you would have to do a lot of panel glue-ups to make those worthwhile. I spent enough on parallel clamps. Guess I’ll keep using those and some nice, flat boards for cauls.

View diverlloyd's profile


3636 posts in 2362 days

#5 posted 01-11-2019 05:23 PM

Bought four of the shopsmith at a auction for a couple bucks. I like them a lot and glad no one else knew what they was. I like you tricks of making them and using them thank you I learned something today.

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