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

352 posts in 2101 days

#1 posted 12-06-2012 08:34 PM

@ PurpleLev: I wholeheartedly agree that there is an important distinction between optimal numbers and acceptable numbers. I’m not suggesting that any joint below optimal will fail. I do however have a cherry kitchen table built by my father-in-law 15 years ago that has 18” glue-line failure. The table is perfect otherwise, there is just the one glueline failure. My guess is he didn’t use enough pressure. I’ve worked with him in the shop so I know for sure he tons of glue (it gets messy). Every time I look at that table, I stare at that glue-line. It’s awful. Non-woodworking friends comment on it. It’s a $1000 table that I only keep around because he made it.

However, if I’m going to sell someone a 2” thick maple conference table that’s 8 feet long, and I know that the optimal force for the glue joints is 230,000 lbs based on the chart above, I’m not sure I’m comfortable using 10,500 lbs using my 10 little pipe clamps. That only gets me 5% of the actual pressure I need.

A good analogy is a car tire. If I look at the tire and see that the optimal pressure is 35psi, but only have a pump that can produce 2psi, should I call it good (that’s about 5% of 35psi). My guess is that even at 2 psi, the car will probably drive acceptably. Just the same, it seems like I’d be cutting it a bit close to the wire.

With all that said, I think you are right. The bench will be fine. I’m going to buy 10 more Jorgenson pipe clamps at $14.00 apiece and call it good. You can never have too many clamps. My experience using high pressure vulcanizing clamps just got me thinking. It’s unfortunately my nature to tinker and think about wierd stuff like this.

Thanks for the reality check though; I need one every once in awhile :)

-- 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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