"Jeff Gorman" wrote in message
...

"CW" wrote

: ............................... Longer planes,
: since they ride the high points, can not get down into the lows to plane
: them. So what you end up doing is knocking of those high spots. It still
: takes a bit of skill but it is easier with a longer plane. I'm not much
for
: explaining things but you probably get the idea.

Coming late into this ..............

It can be shown theoretically, and many know from experience, that all
hand
planes can plane a concave edge. The radius of the curve (assuming it to
be
circular, which it might not be) is proportional to the square of the
length
of the plane divided by the set.

So a 22" jointer set for a .001 shaving (a very skilled user) would have a
radius of 484,000 inches!!! That's gotta be pretty close to flat.

Hence the longer the plane, the nearer the curve is to a straight line.

This assumes normal operation of course, ie trying to plane a straight
edge
(ie not a convex one) with one continuous shaving from end to end.

Most of us want to form a slight concavity when jointing panels where
cramps
hold the material while the glue sets. This has the advantage that the
joint
is more likely to stay closed at the ends as the ends of the panels
shrink
in consequene of long term seasonal changes.

There's some that hold with this, some that don't. Graham Blackburn is one
that don't. See a previous item in this thread where I describe his "rub
joint". OK, I hadn't gotten that far yet, just look below. :-) I think
Graham just uses white glue. Go figure. Guess that's why they wait a bit
before setting the joint aside to dry. Personally, I'm still not absolutely
sold either way. However, there is a certain elegance to a low stress joint
that appeals to my sensitivity.

Depending on how 'perfectly' is defined, it is possible by some planing of
the ends to get two edges straight enough to exactly mate without cramp
pressure. This is how in the past, the workers made 'rubbed' joints with
instant-grabbing 'Scotch' glue (or to the Murricans, 'hide' glue).

Hot glue was applied to both edges, the boards were rubbed together to
remove surplus glue and the panel was laid aside to dry. I've seen men
show off by gluing a rubbed joint and immediately throwing the panel to
the
floor. In my youth I've done it to impress the multitude.

More about panel jointing on my web site - 'Planing Notes' - 'Rubbed
Jointing'.

Jeff G

--
Jeff Gorman, West Yorkshire, UK
Email address is username@ISP
username is amgron
ISP is clara.co.uk
Website www.amgron.clara.net