On 02/09/2014 11:20, robgraham wrote:

I've such a machine, and do just wonder a little at some of the
comments above about parallelism - am I reading that to mean that the
slot cut is accurately parallel with the top surface of the work? If
so I question that as the accuracy of the two joining faces is far
more critical - totally square and totally flat along the length; the
biscuits are a snug fit in the slots but there's enough flex there
while the glue is wet to give a flat top surface as long as the
joining faces are really true.

I have added an illustration of the effect of lack of parallelism to the
wiki page:

http://wiki.diyfaq.org.uk/index.php?..._look _for.3F

With small errors you can in effect twist each biscuit in its slot
slightly to force the parts together - but that does make glueup more
difficult, and also makes it harder to get your top mating surfaces
exactly level - which is one of the key advantages of biscuit jointing
when it works.

The real problem I find with a biscuit jointer, and I think this is
my irregular use rather than the machine, is operating it such that
each cut is accurately spaced from the working surface - now I can't
see how that can vary from a cheap machine to an expensive one as
that does seem to be operator controlled.

Normally you use the fence to index from the show face of the wood. Say
you were edge jointing two planks, you would set the fence to position
the slot approx mid thickness of the board. You then offer the boards
up, and mark your biscuit positions. Now separate them, and each of the
slots in both sides with the fence flat on the top of the board. If the
jointer is accurate the fence to slot distance will be spot on for every
cut and the final joint should be aligned such that the top surfaces are
co-planer.

An alternative is to use a flat work table, and to place the sole plate
of the machine on the table such that you index each cut from the table.
That saves needing the fence at all, but does mean you need to mess
about with spacers if you want an offset from the table of anything
other than the thickness of the jointers base plate.

--
Cheers,

John.

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