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Reply by Nicholas Hall

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Posted on Are Most Benchtops Woefully Underclamped during Glueup? (probably not)

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Nicholas Hall

348 posts in 741 days


#1 posted 631 days ago

@Horizontal Mike: I agree that it could be dangerous to exert these kinds of pressure using air bags. When a compressed air bag blows at extreme pressures, tremendous amounts of energy are released with explosive force. Anyone who has ever seen a tractor trailer truck tire blow can appreciate this. It’s like a ballon popping, only with enough force to send 1” bolts 6” deep into solid concrete. Nobody shoud try this without an airbag professionally engineered and manufactured for this specific purpose.

Using bottle jacks is quite a bit less dangerous. To generate the forces required will only require movement of the cylinder about 1/8” inch. It’s more likely that an i-beam will bend than that anyone will get hurt. That said, I agree that nobody should try it.

That said, if glue joints do in fact benefit from triple the pressure that most woodworkers currently use with their pipe clamps, I think it’s a valid question to ask whether or not there is a better, more cost effective solution to the problem than pipe clamps. Since a $20 bottlejack can exert 40,000 pounds of force, and a $20 pipe clamp can exert only 1000 lbs of force, I don’t think it’s crazy to entertain the following thought experiment:

Is there a safe, effective way to use bottle jacks for panel clamping in the home woodshop?

Put another way: if two $20, twenty ton bottle jacks and $50 worth of hardwood for a total cost of $90 can clamp more effectively than buying 20 rockler pipe clamps at $20 a apiece for a total of $400, I’d be awful curious to know. It’s a thought experiment. It isn’t necessary of course, any more than a 400 pound, $1,500 workbench is necessary. And to your point, it certainly isn’t worth getting hurt over, or risking the safety of others over.

-Nick

-- Outside of a dog, a book is a man's best friend. Inside of a dog, it's too dark to read. -Groucho Marx


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