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My search for the perfect cabinet assembly screw continues.

This research article (rather scholarly and dense, and required 3 readings to fully understand) tested Confirmat screws, screws and mini-fix connectors in particle board, plywood and MDF in various thicknesses.  

The chart shows "moment" (yield strength, or "joint failure") in Newtons/Meter.  It does not matter.  What matters is the relative strengths.

http://www.proligno.ro/ro/articles/2015/..._final.pdf

Chart #4 shows the yield in 18mm (undersize 3/4" = 0.709") as follows:

18 mm Plywood      Confirmat screw      98.10  

18 mm Plywood      Screw                    84.86

18 mm PB              Screw                    44.14 

18 mm PB             Confirmat screw      41.69

18 mm MDF          Confirmat screw      60.82 

18 mm MDF          Screw                    60.33

about a 16% increase in strength.  

Apparently the Confirmat screw behaves like both a screw and a dowel.  It provides both angular support and pull-out strength.

In MDF the difference in strength between the Confirmat and the screw are negligible.   But the difference in particle bard is significant.  And comparing plywood to particle board, the plywood joints are more than twice as strong.

I am going to try the 7 x 50mm Confirmat screws.

(04-03-2018, 09:06 AM)Cooler Wrote: [ -> ]I am going to try the 7 x 50mm Confirmat screws.

I have some here somewhere, and the bits. I hardly ever use PB, mainly ply.
Dig them out so I can use them up.

(04-03-2018, 06:13 PM)Stwood_ Wrote: [ -> ]
I have some here somewhere, and the bits. I hardly ever use PB, mainly ply.
Dig them out so I can use them up.

Apparently the Confirmat screws behave both as a screw and as a dowel.  The screw only holds the two surfaces close together (good for a glue joint).  The Confirmat screws do that and prevent racking (behaves like a dowel).  

I only screw into the edge of plywood if it is supported by a dado to prevent splitting.  I always glue.

There are some cabinet builders (mostly Euro-cabinets, I think) that rely on the fasteners alone for construction.  In that case I definitely would use the Confirmats.

It is rumored that Ikea's engineers have designed a fastener for the RTA (ready to assemble) industry.  It is not clear if they will be licensing it or if it will be reserved for Ikea products only.  It is supposed to be stronger and easier to assemble than what is currently available.  I'm interested in seeing what they've come up with.

They do have plastic cletes that function like sliding dovetails.  But you really would need a CNC router to make efficient use of those.

I have used them for two projects and they work well.  I made some built in bookcases from MDF and they were used for the 90° joints throughout (side grain to end grain).  I also made a futon frame that used them in the frame end 90° joints also.  Although this project was made with oak and pine they worked well in both the hard and softwoods.

As others have said, spend extra for the stepped bits.  They drill a perfectly shaped hole that provides a really tight fit for the screw.  Used properly, I doubt you would have a problem with stripping anything, especially in MDF.