Clamping up a frame

[Philip Florio]

Hi,

I have a red oak frame that is 22 x 30. I'm using a strap clamp to hold it together and it on my table saw table. Once I clamp the four sides, it has a tendency to lift up from the inside. Does anyone have a suggestion to keep it flat. Maybe simply added weight to each piece?

Also the frame is 1 1/2" wide. I'm wondering with red oak maybe I should use epoxy for the mitre joints instead of yellow glue.

Thanks,
Phil

[Chris Gombola]

Phil,
I have not done anything like you are asking, but, if I had to and had the problem you described, I would probably take two pieces of MDF or ply and sandwich the frame between them, thus reducing the chance that my frame is racked at all. My .02.

Chris

[Bill Huber]

I would say your joints are not square to the face.

I would check that really close.

[Mike Goetzke]

Make sure the clamps are centered through the frame - if the clamps are toward the top it will cup like you describe. Also, I tried to clamp a mitered corner raised panel door once that I routered a profile on the ouside of the frame before assembly and it wanted to cup since the clamp load didn't go through the center of the frame.

Mike

[dave rave]

When I need to clamp up a mitered frame I use the frame clamps from Lee Valley:

http://www.leevalley.com/wood/page.aspx?c=2&p=31162&cat=1,43293

Rockler has a version also:

http://www.rockler.com/product.cfm?page=10401&filter=clamp%20frame

I've found they work quite well, but I haven't used them on a frame of that size. One benefit is that you can tighten each corner independently so if it starts to twist you can fine tune it to hopefully correct the problem.

Two bits of advice--1) they can be a pain to assemble and especially loosen because of the nature of the corners and threaded rods.
2) watch out for the knurled nuts--they roll away and disappear in a flash.

[Lee Schierer]

I would say your joints are not square to the face.

I would check that really close.

I agree. The faces of the joint are not perpendicular to the length of the pieces. Your saw blade may not be perfectly perpendicular to the you saw table. Clamping the pieces to a flat surface and holding them flat while clamping may work, but the joint is going to be slightly open on the bottom side if you do that and will not be as strong.

[Jim Tobias]

What Mike said. If you shim under the frame pieces with some thin stock (just enough to get the clamp faces centered vertically on your corners). You should be able to get the miters to close tightly. I have had to do this with narrow frames before when using a a Bessey strap clamp.

Jim