Domino-joint cabinet out of square - FIXED!

[Stan Tillinghast]

I’m finishing up my first serious woodworking project since we left Maui; it’s just a bathroom cabinet for storing toilet paper and the like; but I wanted to use all the tools and techniques I will need for other cabinets. It’s a Euro style cabinet with Euro hinges and solid plywood doors. It has a loose 6 mm melamine back panel in dadoes routed into the top, bottom and side panels.

The cabinet was racked about 1/8 inch to the left.

I used dominoes (5 x 30 x 3 per joint) but did not check for square as I clamped up the cabinet. Yeah, silly.

That was 2 days ago. Now I am able to rack the cabinet square with clamps angled on one side front and back.
Needless to say, the doors did not fit properly; but they are perfectly square, the cup holes seem to be aligned properly (done with LR32).

There is a 3/4 inch space behind the loose panel for a French cleat. Potentially I could use some 3/4 inch ply in a triangle on two sides on the bottom, screw to sides, bottom and to loose panel. Would leave screws showing on inside of panel.

My questions are:
1. Will the cabinet return to out of square when I remove the clamps ( suspect so)?
2. How long should I leave the clamps on?
3. Can I make a permanent correction with this cabinet?
3. How to avoid this in the future? Don’t use loose back panel with Euro cabinets?

 

[ChuckM]

Snip.
My questions are:
1. Will the cabinet return to out of square when I remove the clamps ( suspect so)?
2. How long should I leave the clamps on?
3. Can I make a permanent correction with this cabinet?
3. How to avoid this in the future? Don’t use loose back panel with Euro cabinets?

1) Most likely yes to some extent, unless you're lucky.
2) Depending on the glue. PVA - at least 2 to 3 hours for a large case; make it 6 - 8 to be safe. Overnight for me. Old Brown Glue/hide glue for complex glue-ups, I let it sit for at least 12 hours; 18 - 24 my norm.
3) Can you use a 1/2" ply as the back (rebated 6mm)? If not, add a 1/2" ply to the back (inside) to square up the case.
4) To avoid this, check the diagonals for square as soon as you put glue and clamps on the carcase. If it's out of square, correct it (depending on what glue you use, you may have a window of only 5 to 10 minutes to do that!). Don't use a square to check squareness in a large casework.

You didn't mention it: Dry fit, dry fit, dry fit (and check for square) before you open your glue bottle! If you're using the sub-assemblies approach, check each sub-assembly as you go (image) -- don't wait till you do the final glue-up which could be too late.

If you keep on having problems with squaring, check your domino machine/mortises (are the milled mortises perpendicular?), clamps (are jaws square under pressure?) and assembly table (is it flat?).

If the project requires dead-on squareness, cut a square ply or MDF the size of the internal opening of the carcase and place it inside the case before tightening the clamps.

 

[Stan Tillinghast]

Very helpful, Chuck, thanks.
I’m thinking about using a 1/2 inch plywood rebated for the back in future cabinets.
How best to fasten such a back to the sides, top and bottom? Construction screws are OK if it doesn’t show, but what if one side shows?

 

[ChuckM]

If the back is visible, cut deeper rebates, and glue (or nail sideway) strips (mitered) around like a frame to cover the screws. Or plug the screws...the simplest way?

 

[AstroKeith]

How about a diagonal wire in the 3/4" gap, with a turnbuckle style tensioner in it. Wind it up until square.

 

[Stan Tillinghast]

AstroKeith, I believe thats the engineer’s solution, thank you.

 

[Stan Tillinghast]

I think I’m going to go with a rectangle of plywood behind the melamine panel, and use pocket holes to fasten it to the bottom and sides.
Since I know I can rack it square, all I need is a tight-fitting extra back piece to keep it that way.

 

[ChuckM]

If the cabinet is slightly out of square, the square ply should "lock in" in the cabinet when you push it in. I think a few double-faced tape should do the job of attaching it to the 6mm back for good.
https://www.leevalley.com/en-ca/shop/tools/supplies/adhesives/tape/49224-double-sided-turning-tape

 

[Stan Tillinghast]

I have some double-side tape for laminate flooring that should work. Thanks again.

 

[Stan Tillinghast]

Many thanks to ChuckM.
I did cut a very tight-fitting 1/2 inch ply rectangle, held it in place with pocket screws and double-sided floor bonding tape.
Cabinet carcase remains square after removing Rockler corner clamp.

 

[ChuckM]

Congrats! [thumbs up]

 

[Stan Tillinghast]

I’ll post some photos when I get the cabinet finished.
I have a long list of things I did wrong with this first build, errors I hope to avoid in the future. That’s why we have to get started actually building, right?

 

[rst]

I use a commercial hot glue gun and 23ga 1/4" crown staples to secure my cabinet backs...technology from the 70's.