Thursday, April 2, 2015
After Seven Years, I Flatten My Bench
This week, after nearly seven years, I flattened the ash Roubo bench I built in 2008. If I recall correctly, I've only flattened it once after the initial session in 2008. I've flattened a lot of benches since then, but never touched this one since it didn't need it. It performed fine, especially for planing thin stuff, which should show you how much your bench is out of whack. It was still dead straight along its length, but when I set the edge of my #7 across the top, I could see about 3/32" of light right in the middle.
If you think about that for a moment, you'll realize that that's flat enough for 99.999% of your work. It really is. Why? Because I've built oodles of furniture on this bench in the past seven years, and none of the processes I use (including hand planing nearly every surface) called out for better.
So more than anything, I flattened the bench for looks and grip, since this hollow hasn't affected my work at all.
Nevertheless, here's some points worth mentioning.
Flatness isn't critical. A hollow across the width of the bench isn't a big deal. Unless you're traversing very wide and thin boards, a hollow is workable. Thicker stuff, especially hardwoods, won't deflect. You might have a problem flattening softwood boards that are 18" and wider, as they might deflect into a hollow. Still, I've done that on this bench and haven't had an issue.
Laminated tops can cup. I didn't expect this top to cup. But it did. Others I've made have not cupped to this extent. It's laminated from 8/4 flat stock, so most of the movement is in the thickness of the bench (that's mostly radial plane on the top surface) not across its width.
End caps work in thick massive tops. The end cap on this bench is strictly to accommodate the wagon vise, but it's actually done a fair amount towards keeping the top flat. In the first picture, I've made about eight passes with my #7, set for a heavy cut. On the fourth pass I was taking full width shavings across the grain about 1/4 down the top. This told me that the end cap had kept the top flat towards the end, and less so farther down the top. In fact, the opposite end of the bench was the most deeply cupped. It has no end cap. So, was the end cap keeping it flat? Or reducing moisture exchange? Probably both. So far all of you who've built benches with two end caps (even though I told you the second was unnecessary) nice move.
All work and no plane make jack a dull blade. Seven years of dust, grime, bits of steel wool, dried finish, dandruff, and skin cells from my Turkish apprentice, allow maybe three passes before the edge of a plane iron becomes a toothing blade. I sharpened five times to flatten this top. I took eleven passes total.
Traverse, and walk away. The best surface texture for a bench top is a toothy one. No, not necessarily one made by a toothing plane (although that works just fine) but the toothy surface you get from planing directly across the grain with a generous cut, and a cambered iron. When I finished this bench, the top was smooth planed because I wanted it to look like furniture. Yes, I'm guilty. But I admit the folly of my ways. Traverse your top, let it be toothy, and your work will stay put.
No finish is the best finish. I once thought two coats of an oil varnish mix was a perfect finish for a bench top. Enough to keep it clean, that was the goal. But even that thin coat, when applied over a stupidly smooth-planed surface will burnish and polish, and make a slick, hard surface after seven years. The opposite of what you want in a bench top. I would sacrifice the convenience of not having to worry about glue and finish drips at the cost of an ideal surface any day. You can always use a drop cloth on the bench if you need to glue or finish on it. Will an unfinished bench get dirty? Yes. But that will urge you to clean it with your jointer plane. Which brings me to my next point.
Flatten your bench often. Flattening benches is not fun. Okay, maybe the first time, or after a sweet build, but never because you have to. I would rather freshen the surface once a year every year with a pass or two, than the dozen passes this bench required.
Light surfaces are best. The oil varnish on this bench had really darkened the surface. Now it looks bright and fresh, which I like. I'm always after more light, and lightness in the shop.
This bench is now ready for Handworks, where you can see it at the Sauer and Steiner booth. So now you know the real reason for my flattening session.