Thursday, November 28, 2013

When in doubt, use a bigger hammer.

I love watching the videos from Richard Maguire. And I like reading his blog, too. He knows his business, and gets down to it, and there are no unnecessary frills or showmanship involved. Which is very cool, and feels a little novel, coming from the North American blogosphere sometimes. A while back, Richard wrote that he'd taken to using a lump hammer instead of a wooden mallet.

I've been paring a lot of angled mortises this week. I gave in to temptation the other day and grabbed the 3 pounder that I usually use for hitting a center punch, or other appropriate tasks, and started putting it to the back end of one of my wooden handled mortise chisels. I felt bad about it for a minute, and worried that I'd do some real damage, but then I thought about the math involved. When you hit the chisel, the energy that drives the chisel forward comes directly from the inertia of the whatever you're hitting it with. And the two factors that go into inertia are mass, and velocity. More mass equals more inertia... or, the same amount of inertia, but with less velocity.

You tap slowly and lightly with a much heavier hammer, and apply the same amount of force behind the chisel as you would by whaling away with a joiner's mallet. But the handle isn't going to receive the kind of shock load that you'd get from something that you have to swing much faster. It's a little counter-intuitive to me that a 3 pound sledge would be actually be gentler to my tools than a wooden mallet, but the more I think about it, it's probably true. And that's been Richard's experience, too: "I’ve broken several chisel handles with a wooden mallet and yet to break one with Lumpy." (Lumpy is his trusty lump hammer, that he's been using for years.) And while I can't really prove it one way or the other, I'm starting to feel like it's showing in the work, too... The chisel is being shoved rather than being blasted through the material, and it feels like a cleaner cut.

I will say to take your time and listen to the hammer if and when you use it... After the first day it felt like I had strained my bicep, because I was throwing the 3 pounder around like it was a lighter tool, jerking it around and shock loading my arm in the process. Using a hammer like that is not about power... It's about finesse, and letting the hammer move as it will. Once I got used to slower moves, it was a much more enjoyable experience. 

1 comment:

Robert said...

This is an interesting idea. Though I wonder if the reason that Mr. Maguire has not broken handles has more to do with greater control of the mallet at slower velocities.

Force equals mass times acceleration, so with a larger mass, less acceleration is needed to achieve the same force - but conceivably with the two regimes (less mass * fast versus greater mass * slow) the forces could be equal. Perhaps the greater control of the vector of the force relative to the handle prevents off-center or otherwise errant blows - leading to longer handle life. Whatever the reason, it is a nice insight.