Square Cabinets, Backs and Rabbets

[Prizen]

Hi all

I will own up, I cannot get my cabinets square. For example on kitchen base cabinets I use dominos and up to now, have used 20cm deep brace / cross member at the back and top.

I see many in the US use a thin back panel rabbeted in. I’m thinking that this is popular as they nearly all have dado blade setups.



What is your approach to cabinets, and specifically, making them square?

Is the sequence glue up as fast as possible and get the back panel in as the last step and before the glue dries?

 

[doctor Bob]

If they are just a few mm out on kitchen units it's not the end of the world as they can be squared up during the fit.

Are you sure your saw is cutting a perfect 90 degrees?

 

[Prizen]

Yes the saw is cutting at 90

 

[Sgian Dubh]

Are the two sides the same length? Ditto that question for the top and bottom pieces? Slainte.

 

[Distinterior]

What are you using to cut up the panels? A panel saw?.... a Track saw...?

 

[Jacob]

Not obvious but making the backs rigid and square can make the problem worse in that any movement in the structure will show at the front instead, with badly fitting doors or drawers etc. Trad cabinets have loosely fitted backs.
It's the front which matters most and how the joinery holds it square, which is obviously not good enough in your case!
Maybe a photo?

 

[Cabinetman]

If they are just a few mm out on kitchen units it's not the end of the world as they can be squared up during the fit.

Are you sure your saw is cutting a perfect 90 degrees?

It may look 90° when you’re checking it but it would hardly need to be out at all to really throw off a cabinet, suggest you stand a cut piece on edge on top of a cabinet side and check it that way rather than trying to measure the blade angle. Ian

 

[Prizen]

Thanks all. I am using a track saw first, then a DeWalt DW745 table saw. I will check a piece by standing on edge

 

[Hornbeam]

I am just finishing a series of kitchen units in oak veneered birch ply using domino construction.
Backs are 4mm loose panels slid into grooves from the top after glue up
The back has a top cross piece which is 100mm wide so generally sets things square.
Clamp position is critical to getting the carcase square. If the sash clamps are slightly off parallel with the shelves they will tend to pull things out of square. You can use this to adjust squareness of the carcase or place a clamp diagonally corner to corner to pull back to square (it doesnt have to be a clamp, I often use a loop of thin rope and a windlass effect
Gluing up cabinets this size is also much easier if done by 2 people on a good flat reference surface
As Jacob said squareness at the front is more critical than the back but neither should be far out
Ian

 

[Dee J]

If your cabinet is glued and clamped while resting on its back on a flat surface, and you check and adjust for equal diagonals on the front before you leave it, then you shouldn't be far out. If you can't get it clamped flat and square then some component is out.

 

[Doug71]

Does your Domino cut dead square? The 90 degree detent on my DF 500 is slightly out, I have to slightly lift the front of the base on mine so it resets to the top side of the detent for it to cut square. In theory you are doing opposite sides so one should cancel out the other but might be worth a check anyway.

 

[Prizen]

Thanks all, lots of great suggestions there that would never have occurred to me.

Glue is set now but will definitely work through each of these.

 

[peter-harrison]

I've noticed that with the domino too- it has caused me a few problems with doors. Another thing that might be happening is that your panels may be out of square- have you checked by measuring the diagonals?
Pete