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Dusting Off the Anvil
One of my favorite books is “The Magic Christian.” It’s about an eccentric billionaire who likes to play practical jokes. In one scene, a man busts up a section of sidewalk with a sledgehammer while another man stands by wearing a white lab coat, holding a clipboard. When a policeman comes along to question them, the man in the lab coat says “This is a test.” So the policeman leaves. My best friend in high school maintained that a person could go anywhere in the world without being questioned as long as he was wearing a white lab coat and carrying a clipboard. I’ve never tried it, but I have been tempted. You can get away with a lot of nonsense when you pretend you’re a scientist.
When woodworking magazines publish “scientific” tests that claim to prove the best or strongest joint, glue or whatever, I think about white lab coats and sledgehammers. These things are interesting, but they don’t prove much. We try to keep this in mind when we get tempted to pretend we work for Underwriter’s Laboratory, so instead of conning real scientists into letting us use their instron machine, we dust off our collection of anvils.
We’re feeling the urge to smash some stuff, now that we have a video camera and a Festool Domino. We’d like to invite our readers to suggest other joints they would like to see tested. We have a few in mind: We’d like to look at mortise-and-tenon joints that are poorly proportioned or pegged with oversized dowels to see how they compare to those same joints done properly. Maybe we should test bridle joints glued with reactive polyurethane and see if clamping makes a difference.
Leave a comment (just click on the blue line that says “Comments” below right, or send me an e-mail with your pick). I’ll tally the votes and we’ll drop the anvil in the next couple of weeks.
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With Independence Day fast approaching, perhaps more excitment could be had in the old Southern tradition of "blowing" the anvils, as described in Alex Bealer’s classic The Art of Blacksmithing (Castle Books, 1969) Two smithy’s anvils were stacked base-to-base, the hollows filled with black powder and a length of fuse. Your imagination can supply the rest.
Now, if we were to GLUE the anvil bases . . .!
Keith-
That’s the point, there isn’t enough difference in strength from glue to glue to really make a difference, especially when all are more than strong enough. Instead of some hokey test to say this is best, why not an intelligent discussion of the other factors that enter into what glue to use in what situation. I think we have a responsibilty to further the knowledge and understanding of the craft. Part of that may be to say "the Emperor isn’t wearing any clothes".
Bob Lang
Your idea of properly-sized vs. awkwardly-sized tenons & dowels is definitely worth doing. Try making a series of 4-5 sizes in 1/16" thickness increments.
Pick the best, and repeat with changes in width. If you have enough datapoints to draw a little graph, that’s much more informative than just giving a number.
Or marking a particular method as "Editor’s Choice." Whatever method you use to make them, make sure it’s accurate & repeatable.
Haunched vs regular tenons might also be worth it.
Hand-chopped/sawed vs machine-cut vs biscuit vs domino, to get an idea of the importance of fit. Perhaps you could come up with a way to quantify how much empty space remains in each joint once the tenon is inserted? It’d obviously be small for the domino, but how much worse is a hand-made joint?
And finally, and perhaps most informatively, please compare a joint made by you, Chris, and your art director (who, if I recall correctly, blogged that she’d just made her first dovetail a few weeks ago). How much strength payoff can we slobs expect to see from cutting all those practice dovetails and tenons?
Hmmm. I’m sure you’ve seen the uproar at some other magazine’s forum web site. Feeling demolition envy, are we Bob?
I still (until proven otherwise) trust the ASTM http://webstore.ansi.org/ansidocstore/product.asp?sku=ISO+6238%3A2001 figures at Titebond.com.
Since the results are within 10% of each other, what it says to me is that a good fitting, clean, well-glued joint is more important than which particular glue I choose. So I should choose a glue based on other criteria. One tests at the Titebond site, though, are epoxies, resorcinol, CA, and other glues that Titebond apparently does not make.
However, since you asked, Domino vs. std mortise & tenon vs. shop-built loose tenon.