Biscuits can be used but you cannot glue the breadboard all of the way
across the table end. You have to allow for expansion or you will split the
end of the table or fracture the joint - more likely the table will give.
You can glue and biscuit the center 1/4 or so, depending on the width.
Outside edges should be allowed to move and the biscuits can assist with
this too, HOWEVER, you should use a more rigid mechanical fastener in
slotted holes (bolts, screws, etc.) with the biscuits. That is what the
mortise and tenon or spline does.
A clarification - the outer biscuits are not glued in both pieces, only one
if that. The outer edges must slip. You cannot depend on these biscuits
for strength - just alignment. The hardware provides strength.
A good reason you can't. The movement of the main tabletop if glued to a
breadboard across it's width will definitely split your breadboard (or the
table top itself) over time. The purpose of the mortise and tenon for a
breadboard isn't usually to provide a gluing surface. It's to provide a
joinery/mating system that can then be pinned or fastened to allow for the
constant expansion and contraction of a solid wood table top. That's why you
often see breadboards that extend slightly beyond the width of the top
they're connected to. That's to allow for expansion.
You could try a single glued biscuit in the center and then try unglued
mortise and tenons further out along the edges. You can then pin the tenons
with a through or partially through dowel where the dowel hole in the tenon
has been elongated across its width to allow for movement. Think the easiest
is to make the end of your tops one long tenon and then your breadboard have
a matching mortise/slot across it's length. Then dry fit to your table top
(allowing extra breadboard length than actual width of your table top),
drill holes to pin the tenon into the breadboard, take it apart - widen the
holes across the width of the tenon. Then put back together with a little
glue in the center and lightly glue the pins into place. Lots of good arts
and crafts/craftsman style plans or books demonstrate this.
Rule of thumb I've seen is allow for an 1/8 inch of expansion for each 12
inches of board. Of course, that will vary a lot depending on the woods
you're using but it's a starting point.
Just my 2 cents.
Gary in KC
You could use them if you wanted to "glue up" a breadboard, but that's
not itself a good idea.
The idea with a breadboard end is that the ends are only fixed in the
centre, so that they can allow for moisture movement in the main board.
They're not even held with a mortice and tenon - it's more of a tongue
and groove and the tenon(s) (if any) are cut with over-width mortices to
also allow this movement.
If you biscuit a breadboard end on, something is going to warp or crack
somewhere. Of course if the top is actually veneered plywood or MDF
(stable against moisture changes), then you could do it.
Re my earlier post - the tongue and groove or spline is really a very safe
choice - and not that hard to execute. The combination biscuit/metal
hardware joints I mentioned were in a 8/4 oak coffee table top and I didn't
want the exposed spline on the ends. I could have achieved this appearance
with a hidden spline but the biscuit/slotted-hardware approach was an
experiment. Appears to be successful as the table is about 3 years old;
lives in an Arkansas home with partial wood heat and lower than average air
conditioning. I have seen the joint edges move as much as 1/16" in or out
(21" wide) but everything looks fine.
Some side information - with the wide top and ends I have two layers of
biscuits in three places. Two pair surrounding a bolt at the center (about
six inches glued in the center area) A similar biscuit/bolt cluster about
six inches in from each edge - these biscuits are lightly glued in the table
top only - not the ends). The bolt holes and biscuit slots at the end
locations are slotted oversize to allow for slide.
By the way, if cutting spline slots on your saw or with a router makes you
nervous, consider using your biscuit cutter. If you take your time and
apply a little finesse you can machine a nice blind slot with the machine.
Most machines do more than one thing.
Yes, but cause the joint will eventually break and will only be held by the
biscuits. I can tell you from experience. I built the NYWS bedside table.
And used a tenon and slot in the breadboard edge. I have had the table for
5 years now, no problems. I built one for my sister later and decided to
take a short cut and just use some biscuits. The edge on this one has
broken loose and is only held by the biscuits. It is almost 1/4" off on one
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