Squaring up a cabinet using band clamps

[Howard Rosenberg]

I've used conventional clamps on the diagonal to square up carcases before.

But this weekend I'm starting a biiiig one. Seven feet long. Longer than any clamps I own. And the diagonals will be that much longer. So I'll use my band clamps. My biggest concern is, if I need to, how do I square up a cabinet when the primary clamping is from band clamps.

Any ideas?

Thanks.

Howard

[Sam Murdoch]

I don't know that you can unless you can truly go corner to corner at the front and back with 2 separate clamps. Sometimes a cabinet can be out of square on the front and not so bad or in another direction on the back.

Alternatively, do you know you can connect one clamp to another to make one longer clamp? 2 short clamps meet in the middle and grip each others pads while the other ends are holding the cabinet - sounds kinky but it does the job. :)

Don't know what kind of cabinet you are building or how the back is attached or fitted but it can help immensely if you make certain that your cabinet back is as precisely square and as exacting a fit as you can make it. A well fitted and square back set within a dado will do a lot towards squaring the cabinet. If it a full overlay back, attach it directly to the cabinet with screws, working with confidence from one corner to the other. Even if you need to remove it later for finishing it will keep your cabinet square as the glue dries.

[Charles Lent]

I have several pipe couplings to use with my pipe clamps just for this purpose. Whenever I need a few longer clamps I take apart several of my pipe clamps so I can couple several lengths of pipe together to make the extra long clamps that I need. Without couplings my longest clamps are 48", but I have made up extra long versions to assemble projects up to about 10'. I now use Bessey clamps for most of my 42" and shorter clamping needs, but still keep the Pony pipe clamps around because they can provide this extra long clamping ability.

Charley

[Jamie Buxton]

Or you can make a long clamp from two short clamps and a 2x4. Or use the offcut plywood instead of the 2x4. Put a hole or a notch near each end of the 2x4. The clamps run from those holes to the cabinet corners. Of course it is clunky, but for occasional use it does work.

[HANK METZ]

While diagonal measurement is very telling if a case is square, it doesn’t account for a parallelogram end result (a flat shape with opposite sides parallel and equal in length). In other words your two measurements may agree but you could still not be square. Use the 3-4-5 rule to establish that one corner is truly at square, then compare the diagonals. In smaller structures a carpenter’s square will suffice in checking for square. I was introduced to this phenomenon way back when assuming a sheet of ply was square, as almost all are, I made my parting cuts and none were square, all were parallelograms, just off enough to be quite annoying but correctable in the end.

- Beachside Hank
Improvise, adapt, overcome; the essence of true craftsmanship.

[glenn bradley]

Squaring assists?

265784265785

[Dave Parkis]

Can you clamp/attach squares/assembly braces to the inside corners? If you can, they will keep everything square while you use the band clamp. I know Lee Valley sells them as assembly braces. Here's a link to a pic. http://www.leevalley.com/US/wood/page.aspx?p=51101&cat=1,43838,51101

[Kevin Jenness]

On the contrary, if the diagonals of a parallelogram are equal, the parallelogram must be a rectangle.

To the original question, you can do as Sam Murdoch suggests and use the back as an assembly aid, or use a smaller square piece (or two, front and back), clamped temporarily into one corner.

[Michael W. Clark]

Squaring assists?

265784265785
+1 I have some very similar and use them all the time.

[Michael Dunn]

While I've yet to build one that large... I use ratcheting the downs across the diagonal that is too long. I typically tighten it a little bit too much since it tends to spring back a bit when you release the band.

[Dave Zellers]

Get it close to square then lay a strip of 3/4" ply (use pine if over 8') about 4" wide across each diagonal and carefully trace the angles of each corner underneath. Label the ends and corners. Cut one end perfectly on the lines. Cut the other end maybe 1/8" short. Insert both inside the cabinet and shim with a tapered shim until the diagonals are perfect. If the opposite sides are the same length, the box will be square. Don't remove them until you absolutely have to. Hopefully, that will be after transportation to the final resting place. Sometimes I have to remove them for finishing but put them back for moving and drive a screw at the intersection to lock them in place.

[Bruce Wrenn]

On the contrary, if the diagonals of a parallelogram are equal, the parallelogram must be a rectangle.Best I can remember, a parallelogram only has two side which are parallel. When it has two sets of opposites sides parallel, it a rectangle. A parallelogram can have equal diagonals, if the two non parallel sides are the same length.

[Dave Zellers]

By definition, opposite sides of a parallelogram are parallel. That being the case, opposite sides must be of equal length.

[Mark Bolton]

While diagonal measurement is very telling if a case is square, it doesn’t account for a parallelogram end result (a flat shape with opposite sides parallel and equal in length). In other words your two measurements may agree but you could still not be square. Use the 3-4-5 rule to establish that one corner is truly at square, then compare the diagonals. In smaller structures a carpenter’s square will suffice in checking for square. I was introduced to this phenomenon way back when assuming a sheet of ply was square, as almost all are, I made my parting cuts and none were square, all were parallelograms, just off enough to be quite annoying but correctable in the end.

- Beachside Hank
Improvise, adapt, overcome; the essence of true craftsmanship.

This one threw me for a bit of a curve ball but..
http://wiki.answers.com/Q/In_a_parallelogram_are_the_diagonals_equal


way back when assuming a sheet of ply was square, as almost all are

I dont think I have ever had a square sheet of ply land in the shop. Many may be lucky enough to have a single square corner but even thats not often the case. One of the reasons sheetgoods are 48.5" x 96.5". Subflooring and roof sheathing, or perhaps even cheap paneling, is far more square than "cabinet grade" ply we keep in stock.

[johnny means]

Some of us need to brush up on geometry:rolleyes:.

[zayd alle]

Howard,

To answer your original question, you can use spacers on the outside of the corners that are less than 90 degrees (the long diagonal). Then run your band clamp around the perimeter and tension until those opposite corners are pulled in square.