Thread: Real truth about assembling melamine cabinetry

Unless you have self-countersinking or funnel head screws, yes

Originally Posted by woodPixel

Dumb question here... So kitchen cupboards are essentially held together only with a few screws?

No glue?

They are chock full of cups, plates, pots and other heavy stuff.... And all of this is reliant on not having 3 screws pull out?

That's really amazing.

Consider a cabinet carcass. It has two side panels, a base and a top or top frame and a back, plus possibly some fixed shelves if large enough. Everywhere where there are joints, there are normally a minimum of three screws along the joint unless a particular component is so short or narrow to practically fit three screws without weakening the structure. So for example, a wall hung upper cabinet over a bench normally has a minimum of nine screws for the top or bottom panels, three connecting each side and three connecting the back. Both side panels have a minimum of nine screws, three securing the top panel, three securing the base panel, and three securing the back panel. The back panel typically has a minimum of twelve screws, three securing each of the top, base and two side panels. Adding a fixed shelf adds an extra nine screws, three from each side and three from the back, so for the carcass to fail normally requires more than three screws pull out.

The business I worked in had about a 50/50 mix of new builds and refurbishments, so I got a fair bit of experience breaking up older carcasses that had been removed, this ranged from a decent hit with a mallet to shatter a 3mm MDF back and a decent kick or push to collapse the carcass for a cheap poorly constructed 'softback' cabinet, to 6 to 10 decent blows with a mallet per panel distributed around the various seams to break up a solidly built 3 screws per joint carcass.

Also consider that any adjustable shelves of regular shape and moderate size are typically supported by five 5mm dia pins set 6-8mm into the side panels, and the limiting factor is the sag of the shelves rather than the failure of the pin sockets.

So no, your crockery and pots and pans should be safe and are not reliant on just three screws not pulling out.

Originally Posted by Arron

A couple of questions on pilot holes.

How do you drill the pilot holes, making sure they are well aligned with the centre plane of the board. Especially an issue if drilling freehand. I’m thinking of maybe making some kind of jig out of hardwood, but interested in what others do.

Cheers
Arron

In our case, all holes at right angles to the face are drilled or bored by the CNC, so you set up global profiles in the software for positioning them so they land along the centreline of the mating panel. Then when the mating panel is flush with the edge of the drilled panel, the screw hole will be on the centreline of the mating panel, and you have the predrilled hole as a drill guide to drill the pilot hole so manual drill aiming is not as critical as it would be for freehanding each hole. CNC screw holes were 3.5mm (tight for screw shank) but the same diameter as the pilot drill bit, screw is positively advancing for the full length of the screw.

We used self countersinking screws, so did not need a second pass with the CNC to countersink screw holes.

Originally Posted by Arron

If you are using brads for alignment and drilling just one combined pilot/clearance hole then it’s easy to see that any speed advantage from using glue is lost.

They were bradded and glued only. No screws, no drill. Still way to slow due to slippery alignment and the need for glue clean up.

I've also got a question to add to this thread if I may?

What is the "standard" size for screws for 16mm chipboard/melamine? What about 18mm? 12mm? I'm talking in terms of screw gauge here, and length.

I did pick up the "50mm" mentioned above, but is that applicable across all thicknesses of panels?

Thanks in advance for any information, and apologies on the thread hijack!

I believe the rule of thumb is 1/3 through and 2/3 in. We used 50mm for 16-19mm material, 70mm for thicker stuff and 30/40mm for thinner stuff; Hafele Hospa and Wurth ASSY, no idea what gauge they are but the Hafele ones like a 1/8" pilot and the Wurth ones are thinner, maybe 2.5mm