Pressure from Clamps from WoodCentral
Perhaps 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. - Editor
"Let's say I clamp two flat boards together. Is there any way to figure out how much pressure (pounds per square inch) is exerted?" - Eliot D.
The first response indicated that clamps manufacturers do indeed provide ratings for their tools -- but many other factors impact the actual pressure. - Editor
"Each 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.
Other responses provided a mathematical formula, a specific tool to measure load, and the difference of force vs. pressure. - Editor
"Add 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 Understanding Wood,says that pipe clamps can exert 1,120# and F-style heavy-duty quick clamps can put out 550#." - Ellis W.
"There 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." - Tony
"With 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. The 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." - Rick C.
The original poster eventually clarified his project -- and appears to have received a simple answer that satisfied him. - Editor
"Most 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.
"What if you made a disc or square of known area and used it on top of a decent bathroom scale in the press?" - Tony
"This would work. Why didn't I think of it?" - Eliot D.
Old Band Saw Motor Problems from Woodworking.com
This woodworker's very, very old band saw quit working -- kind of. He wondered whether he should replace the motor, or attempt to fix it. - Editor
"I 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.
I 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" - Derek
Some responses offered suggestions for what might be wrong, and how to fix it. - Editor
"Sounds 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. With 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." - Frank C.
Others gave him options for where to find replacement parts -- or motors. - Editor
"You 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
With 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.
"I 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.