Clamps from WoodCentral
influenced by all the power ratings on power tools -- or maybe he
just misses math class -- this woodworker wondered if there was a way
to figure the specific amount of pressure in a clamping setup. -
say I clamp two flat boards together. Is there any way to figure out
how much pressure (pounds per square inch) is exerted?" - Eliot
first response indicated that clamps manufacturers do indeed provide
ratings for their tools -- but many other factors impact the actual
pressure. - Editor
manufacturer will have data on their clamps about a clamp's rated
pressure. So if you tighten a clamp fully, then you would be at its
full pressure rating. Without a gauge, anything less than fully tight
is anyone's guess. That said, does it matter? When clamping two
boards, there are many other factors about how tight to apply
pressure. Type of wood, thickness, etc. are factors. The desired
result is generally the same: edges pushed together squarely without
open seam." - Thomas S.
responses provided a mathematical formula, a specific tool to measure
load, and the difference of force vs. pressure. - Editor
up the sum total of the clamping pressure of all the clamps you're
using and divide by the surface area. Many typical woodworking clamps
have reasonably known maximum pressures; e.g., Bruce Hoadley, in
Wood,says that pipe clamps can exert 1,120# and F-style heavy-duty quick
clamps can put out 550#." - Ellis W.
have been several articles about this subject. Most of them have a
table that shows typical values for each type of clamp. I would use
that as a rough guess. Now, if you really want to get technical, you
could measure it with a load cell or something similar. There is a
company out there that sells a material that measures loading and
creates a graphic image (nice colors) of the loads. You can buy
inexpensive load piezo cells and calibrate them and measure using a
small ad board or micro. Probably lots of info like that on Google."
a lot of woodworkers, there is some confusion over the difference of
force versus pressure, and this applies to how they wish to clamp
their boards. The clamp creates an absolute force. It is only when we
examine the size of the joint were the term pressure comes into play.
pressure at the joint is the force of the clamp divided by the
surface area between the boards. Most clamp manufacturers will
publish how much force their clamps are capable of achieving.
Granted, even this information is very subjective."-
original poster eventually clarified his project -- and appears to
have received a simple answer that satisfied him. - Editor
woodworkers look at things like glue-out, etc. I am working on making
a kind of press used in printmaking, where the pressure is of
considerable importance. I certainly know how how to figure it once I
know the force exerted by the clamp(s). What I don't know is the
force. (I have some old, nondescript boat makers clamps, for
example.) And I'm not even using clamps; I've set up some cauls with
bolts and nuts. So the plot thickens." - Eliot D.
if you made a disc or square of known area and used it on top of a
decent bathroom scale in the press?" - Tony
would work. Why didn't I think of it?" - Eliot D.
Band Saw Motor Problems
woodworker's very, very old band saw quit working -- kind of. He
wondered whether he should replace the motor, or attempt to fix it. -
have a very old band saw and motor. Right now, the motor still works
-- kind of. When I turn on the band saw, it takes about 5 seconds to
get up to speed, which it did not do a few days ago. Next, I can saw
for about 15 sec until the motor starts to smoke. I don't know if I
should go for a different motor (I can't find an identical one
anywhere) or see if I can fix it.
do not know what is wrong with the motor and did not know if anyone
could guess. Here is the manual for it http://vintagemachinery.org/pubs/detail.aspx?id=2920"
responses offered suggestions for what might be wrong, and how to fix
it. - Editor
like the motor is only running on starting windings and not switching
to main windings. If you remove the belt and start the motor, do you
hear a click when it gets up to speed? Have
you tried blowing the sawdust out of it? Sometimes this helps, but
the smoke you mention is never a good thing.
that type of motor there should be a definite click when it comes up
to speed. 1/3
hp motors are very common, and can be picked up used for very little,
so if it is a matter of getting back to work that is probably your
best option, unless it is important to have a motor from the same
period as the saw."-
gave him options for where to find replacement parts -- or motors. -
likely have a bad coil. If you are wanting to keep the saw original,
you can take the saw in and have it rebuilt by a rewinding shop;
otherwise, you can order a new motor with the same frame size and
bolt pattern. You
can get a rough idea of what it would cost for rewinding / rebuilding
here - http://eurtonelectric.com/catalog/motorreplaceform
a bit of searching, you can probably find a similar sized motor on
eBay. Just depends on what you want to do with the saw in regards to
keeping it original." - Bree S.
buy all my replacement belt drive motors at the steel recycling
centers. They will normally have a bin of them, and you pay by the
pound. If it is the size, speed and horsepower you need, spins
smooth, doesn't smell burned or show too much internal damage, I find
about 80 percent work fine. Of those that don't, about 80 percent can
be fixed with a new cap or cleaning the startup switch. Before I did
anything, I would pull yours apart and clean/inspect; what have you
got to lose? Bad thermal switches are another failure point, I find."
- Ken N.