14 March 2010

Dowels


Looking at the latest video of the Woodwhisperer where Marc demonstrates the DowelMax, I thought about all the dowelling possibilities and jigs.

Dowelmax is interesting as it brings dowelling to heavy frame constructions where tenon and mortices are normally used.  Dowelmax helps with high density dowelling with there (multiple) allingnments of closely placed holes.  The only problems are the price and dowelling on larger length as the jig needs to be repositioned and the appearance of cumulative alignment errors .

Dowelmax makes strength tests and came out as a winner out of its own tests. So yes, five 5/8" dowels are much stronger than a single 1/6" number 20 biscuit   Of course things can be different once the tests are made by a third party (in this case FWW).  I think that the main difference between both tests is that standard routed mortice and tenon joints are deeper (2") than the standard  1" (25,4mm) dowel depths.  With limited depth the Dowelmax falls for FWW in the same category as biscuits, festool dominos and pocket joints where the wood of a L joint will easily split at the shallow depth of the holding element.  At Dowelmax they redid the tests with 2" dowel depth greatly improving the results.  I agree with them, my first impression of the FWW results for dowelling, biscuits and pocket holes is that strength can be improved by working on depth.  More on this another time,  as I already made a few joint tests with my own set up.

As Marc correctly mentions James Krenov was a dowelling adept.  His jig, as decribed in  'The fine art of cabinetmaking' and probably FWW isues, is a long piece of hardwood with predrilled holes. "The whole secret of doweling, and it is somewhat of a secret because of lack of common knowledge, is accuracy. You must be absolutely accurate. J.K." This indicates one advantage of biscuits and dominos over dowels,  the alignment is less strict.  In the case of long pieces the advantage of this jig is that it is only positioned one time.  Krenov uses his horizontal mortiser for drilling,  improving with this the alignment of the drill.

Wolfcraft offers different dowelling jigs.

The first is a cheap self centring  hand-held device for the classic 6-8-10 mm dowels.  This gives you one hand for the jig and one for the drill as not much is foreseen to fix the jig (there goes my insight gained by reading James Krenov).  As I bought a cheap copy of this one, I should maybe add a water-level to my drill to achieve the necessary accuracy.  Added to that the centring part does not work at the border of the wood, and of course multiple rows are impossible. The second hole is done aligning the jig on a a dowel in the first hole.
The second works with (6-8-10 mm) drilling bushes and has predefined drilling heights.  The holes are directly set on both sides, avoiding realignment problems. Works for I, L, and T panel joints
The last jig is more for shelving with a standard 32 mm spacing between dowels and 5-6-8-10 mm drilling bushes