How to extend the throat of a pipe clamp?

[Bob Jones]

I have a bunch of pipe clamps (only kind). They are 1 7/8" throat (from the pipe to the top of the clamp). I am about to glue up a top that is 4in thick, but I can't afford a bunch of new, big clamps. Anyone know a good (&cheap) way to do this?

I was planning to use a caul, but need to figure the depth out. Pictures are welcome!
thanks

[John Coloccia]

How about a clamp on top and a clamp on the bottom?

[Bob Jones]

yeah, well the top is +8ft long and I have 12 clamps - not really enough to do that IMHO.

[johnny means]

Just alternate your clamps from top to bottom. All you really need to do is avoid the tendency to cup.

[Lee Ludden]

If you alternate above/below, and then instead of clamping to the sides of the assembly, you clamp to cauls stretched diagonally between them, that would probably work.

The clamps would have about 12" between them.

I'd seriously consider just buying more clamps rather than risking a bad glue up. You can get the standard pony clamps at BORG for about $14 each + $7/10' length of pipe, so about $18/5' clamp. Even 5 or 6 more clamps would just allow you to alternate above/below and be in pretty good shape.

[John Coloccia]

I've never tried it myself, but I've heard of people using ratcheting straps with success....and Harbor-Freight happens to be having a sale.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47708

If you were going to do this, I'd definitely alternate top and bottom with the pipe clamps to keep everything in alignment.

[Kent A Bathurst]

Just alternate your clamps from top to bottom. All you really need to do is avoid the tendency to cup.

bingo


101010

[Bob Jones]

Thanks for the advice. The strap is a neat idea. Actually, before I had any clamps I used rope with a stick. Tie rope around joint. Insert stick into rope. Twist stick. PRetty simple and it worked.
I may just buy a few clamps.

[Josh Bowman]

yeah, well the top is +8ft long and I have 12 clamps - not really enough to do that IMHO.
I've now been able to move on to a different clamping system, but for 30 plus years my old pipe clamps did the job and well. 1 clamp on top move down a foot put the next on bottom etc. That is enough and will leave you with extras if you have a hard spot.

[john bateman]

If you have some plywood and a little time....you can make something similar to a clamp pad. It would have the same profile as the clamp faces, only larger, by maybe 30%. They would have a hole thru them and slip over the pipe. You would need to make a pair for each clamp.

(This pic is just a reference...it doesn't show any pads or extensions)

http://images.rockler.com/rockler/images/30921-02-500.jpg

[David Cefai]

This is fussy but it works.

Make up a number of cauls, in pairs for top and bottom. Cover the faces with adhesive tape so they don't get glued to the work.

Drill holes at the ends for bolts. Adjust the hole position to leave space for a flat, wooden pad on one side and a wedge on the other.

Assemble the work on the bottom cauls, put on the top ones, tighten the bolts and drive in the wedges. The cauls prevent cupping and the wedges do the clamping.