Biscuit or dowel? Some interesting facts

[ivan]

Here's the result of some late night reading about the relative merit of dowel and biscuit joints in chipboard and mdf carcasses. Source websites for research papers below.

Max strength dowel spacing ~ 96mm
Max strength biscuit spacing~150mm (edit) 1st biscuit centre 50mm from edge
In general, biscuit joints are around 20% stronger than dowels
Dowelled mdf joints stronger than dowelled particle board.
Particle board joints 10% stronger than mdf where both board edge and biscuit is glued
Particle board joints 55% stronger where only biscuit is glued, but joint has very low stiffness

The results indicate corner joint strength mainly in the glued butt joint, and not in the biscuits. Quote "The biscuits serve to accurately align
the face and butt members during assembly and clamping. They do not really contribute to the strength of the corner joints"


Interesting stuff, especially last line!

http://journals.tubitak.gov.tr/agricult ... 0311-1.pdf

http://www.allbusiness.com/agriculture- ... 147-1.html

 

[dickm]

Particle board joints 10% stronger than mdf where both board edge and biscuit is glued
Particle board joints 55% stronger where only biscuit is glued, but joint has very low stiffness

The results indicate corner joint strength mainly in the glued butt joint, and not in the biscuits. Quote "The biscuits serve to accurately align
the face and butt members during assembly and clamping. They do not really contribute to the strength of the corner joints"

Is it just my reading, or is there something inconsistent between the first two statements and the quote? If the biscuits "do not really contribute", why the difference between the two types of board joints?

Must have a look at the original ref

 

[newt]

I find the statement that biscuits add little strength confusing, in many articles and some of the mags it often recommends 2 and sometimes 3 biscuits at a joint. If they are just for alignment why recommend 3, :?