On 1/16/18 12:20 PM, Leon wrote:
On 1/16/2018 10:37 AM, -MIKE- wrote:
On 1/16/18 8:31 AM, Leon wrote:
-MIKE- wrote:
All this talk of edge glue joints and glue starvation and
clamping pressure and blah, blah, blah.... SWMBO had a request
so I needed to do a quick panel glue-up. Just two 7" poplar
boards edge joined for some little side table thingie that
wimenfolk like. I don't know, I just make sawdust.

So anyway, I just wanted to put in the very minimum effort to
show how just a table saw can do what you need. Also, to show
how little glue is needed (I actually STILL used too much) and
how little clamping pressure and time are needed with modern
PVA glues.

The first 2 pictures shows *one* technique (I have several that
use the TS) for putting a straight edge on a rough-sawn board.
Once you have one straight edge-- flip and repeat and you have
parallel straight edges.

3rd pic shows a thin covering of glue on each edge. Again, I
still think I used to much as can be seen in the squeeze-out in
the following 2 pics.

The next 2 pics show how strong a glue joint is after only a
couple hours in the clamps. Spoiler alert! The wood breaks,
not the glue.

The last pic shows the stained panel and how tight and
imperceptible the joint is.

https://photos.app.goo.gl/pmyWHV7ANvFek7b62



You know, Jerry, the inventor of the Dubby sled uses masking tape
to clamp the sides of small boxes together while the glue dries.
If your Slye edges are true you do not need a lot of pressure.


It's all very interesting to me and always has been a topic that
piques my interest. I still don't know if I've ever seen a
scientific guide to clamping pressure. You'd think it's been done
and is out there, but I haven't seen it.

The masking tape thing really has me curious. At some point, with
masking tape, you have enough PSI on a small enough section to be
as effective as a screw clamp.

I used masking tape to glue plyboo edging on this cabinet.
http://mikedrums.com/bamboo_veneer_clamp.jpg Those "bandy clamps"
from Rockler certainly provide enough pressure.

There comes a point with screw clamps where you have enough
pressure for a properly glued joint and anything more is just
compressing the wood or distorting it. I would argue that point is
much sooner than most of us would believe.

I think I may do a similar "experiment" with several glue-ups using
the same wood but with less and less glue and less and less
clamping pressure.


FWIW long glues ups usually have imperfect straight surfaces. There
is some degree of bend that you may not actually see. Easier to see
if you bring the long pieces together before applying glue and you
see a gap anywhere along the joint. Those type glue ups need the
extra pressure to squeeze the glue out. And I have never had one of
those fail either. The shorter, smaller, and flatter the surface the
less pressure you need to bring the surfaces together.

That is very true. Another thing to consider and a big reason it always
seems to require more clamping pressure for longer panels. Good point.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
www.mikedrums.com