Friday, November 21, 2014

Making Progress: Soft Wood Not So Bad Afterall

In my last post, I mentioned the various difficulties I was having using alder for my changing table. Well, as it turns out, almost all of this was easily preventable! With a bit of reading and some adjustments to my technique, I was able to overcome these challenges, and have been making great progress on the changing table!

As I've been reading about woodworking online, I've seen some pieces of advice repeated over and over again:
  • Prefer wood with straight grain.
  • When planing, take even amounts of wood off both sides of the board.
  • When drying or storing wood, store them stickered, in a horizontal position, off the floor.
There's one other thing I came to realize as I was thinking about it more (and which should have been obvious):
  • Cutting mortises in end-grain is just asking for trouble.
I want to go through each of these in detail, as I explain exactly where I stumbled.

Straight Grain

This is one of my discarded pieces. See how the grain goes
diagonally up and to the right? That's exactly how this
board warped, and became more trouble than it was worth.
OK, so this is one thing I hear woodworkers online repeat over and over again. Straight grain is what you want to work with, curved or slanted grain is no good, or can lead to trouble. But why? I never researched the reason or thought much about it, because I'd never had trouble with it in the past. Much of my wood has straight-ish grain, but I really like highly figured pieces, and so will tend to gravitate towards wood with a lot of grain in all directions. Well, I learned the hard way why this can be important.

For harder woods, I haven't had much of an issue. Cherry, oak, walnut all seem to be very stable, regardless of their grain patterns. At least, I haven't had any issues before. But alder is a much softer wood and has very open grain patterns, much like pine. What I observed from my earlier attempts using it was wood movement perpendicular to those grain lines. Boards I had cut with grain going diagonal tended to warp right along those grain lines. Boards with more knots or changing grain lines tended to warp in more random ways. But my boards with straight grain, running parallel to the long edge of the board, seemed to warp the least.

So, it would seem, straight grain keeps boards flatter!

Even Planing

Another thing I hear all the time is to take equal amounts of wood off a board when using a thickness planer. The reason for this is also wood movement. When planing one face, you expose new wood that likely has more moisture in it than the outside of the board. If you don't also expose the wood on the opposite side, the moister side will dry up, shrink, and cup toward the other face. But, if both faces are planed, wood of the same moisture is exposed, and they'll dry evenly (but see the next point).

This was a big reason why boards I had planed perfectly flat got a big cup in them in the space of just a few hours. Once I started actually planing both sides evenly, that problem went away!

Drying and Storing Wood

My wood stock, separated by stickers (in this case made of
cherry scraps from my jewelry box project).
The last big thing I see all the time concerns how to dry and store wood. Whenever you're working with green wood, or drying your own wood, the advise commonly given is to place boards flat and horizontal on top of stickers (thin pieces of hardwood) which keep the wood separate from the boards they're laying on top of. The wood pile is built up, and then weighed down to keep the boards flat. Keeping the wood stored like this maximizes the airflow around all edges and faces of the wood, and ensures that the wood dries evenly.

Well, it turns out this applies to wood in the workshop too, and even pieces that are being milled for use in a project! When I was cutting my wood, I would get it shaped perfectly, then store it flat, face down, on my wood rack or workbench. Over night, the top face would dry, but the bottom face wouldn't, so I'd find my board cupped downward the next morning!

After discovering this tidbit, I re-stacked all my wood, including the pieces I was using for the changing table. For smaller pieces, I stored them on edge in an attempt to maximize the airflow around them.

I milled the wood, got it perfect, stored it that way over night, and came back the next day to...perfectly flat wood! Now, when I'm done for the day, I make sure the pieces of my project that can be assembled are assembled, and up on stickers (which you can see in the first picture).

Mortises in End-Grain

Mortises in end-grain don't
This should have been a no-brainer. The strength of a traditional mortise-and-tenon joint comes from the side-to-side strength they provide. The tenon can't move in the mortise, because the walls of the mortise are strong. Well, they're not strong if they're parallel to the end-grain!

What happens then is what happened to me. The sides split apart very easily under pressure, causing at best a minor setback and at worst, a failed glue joint. D'oh!

Having realized this, I re-cut my corner pieces, this time with the grain going along them rather than across so the mortises would follow the grain. Much better, now things are holding together very nicely!

∼  ●  ∼

So, I've gone back to my alder changing table, and I'm making much better progress. I suppose sometimes you have to make backward progress before you can really go forward. But it would be nice sometimes if I didn't stumble my way through things the hard way. But on the plus side, this is one lesson I'm liable not to forget! ■

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