Anyone use a biscuit jointer for cabs?

They get tighter, as they swell with glue, to make the fit and joint better. You must use fresh, dry biscuits, to maximise this swelling effect. Once the glue goes off (hardens/cures) the swollen size is then set, by the solidified glue filling the pores of the biscuit. I believe the glue choice to be a bit critical, certainly "Uncle Norm" seemed to always use the Lamello stuff, but I am sure he was given it.

AFAIK water soluble PVA wood glues are required to get the biscuits to swell. Equally, you don't put glue in the bottom of the well, you actually want it smeared on the sides of the rebate well, so it is in contact with the sides of the biscuit, for maximum surface area that is getting "wet", and therefore swelling.

Works in two ways, firstly it is technically an increase in glued surface area, so more glue doing what it does, but also from adding some "keying" to the joint.

I have heard a few use them, but doesn't help that much with speed of manufacture, which is all important for many, especially those doing it for a living. You could probably get away with brads rather than screws, which wins some time back.

Now, P series Lamello biscuits.......

Or really kinky - Invis MX2. Completely invisible bolted connectors. Comes with "Sonic Screwdriver" (well, to my 4 YO sproglet, you could quite easily pass it off as a sonic screwdriver), which has to be cool.

I'm going to build a pair of THAM12s, but they are pretty much for personal use so won't see much abuse.

Sorry if this is an idiot question Joe, how do you line up the biscuit holes on the side panel to exactly match the ones on the edges like in the picture? Do you draw the exact layout on the side piece and then just make the slot dead centre? 

I would have thought with the above that if you are even 1mm out on any of the holes it wouldnt fit?

Basically just wondering how you reference each hole...

Side to side you've got a bit to play with because the slots cut for the biscuits are slightly wider.  All you do is offer the two panels up (or measure) and put a pencil mark on both in the same place.

What's more critical is getting them the same distance from the edge of the panel.  This is achieved just by working on a flat surface and just making sure the base of the biscuit cutter is flush with the edge.

I don't find them much more time consuming than drilling and countersinking for screws.

I'm happy to admit in a production environment they're not the right tool for the job, that's where a CNC machine and rebated joints come in.  However for prototypes, small runs and especially hi-fi cabs they have their uses.