Five tips for milling rough lumber
Milling rough lumber for workshop projects saves money, and it also opens up more creative possibilities than standard, pre-dressed wood. That’s why Art Mulder designed his block set around rough lumber. Success, however, demands more than just running boards through your jointer and thickness planer. Great mill-it-yourself lumber ultimately depends on careful craftsmanship, and the five tips I’ll show you here are the things they never put in thickness-planer instruction manuals.
Cross Cut First, Joint Later
Rough lumber isn’t just coarse to the touch; it’s also twisted, cupped and bowed to varying extents. These changes in shape are just what happens to wood as it dries after sawing. And if this isn’t enough, rough lumber also shows a surprising variation in width and thickness from board to board because sawmills aren’t exactly precision instruments.
Jointing and planing is all about making boards flat, edges square and surfaces smooth. You’ll do yourself a favour by cutting project parts to rough size before milling. The shorter a board is, the less material has to be removed to make it true, all things being equal. That said, never try to joint and plane lumber shorter than 12″ for safety reasons.
Allow Enough Extra for Milling
In theory, rough lumber is sold in increments of 1⁄4″, but in practice you’ll find 1″, 11⁄2″ and 2″ thicknesses are the most widely available. Rough hardwoods are available in 11⁄4″ thicknesses, and you’ll occasionally discover 13⁄4″-thick boards. Whatever you find, make sure you choose boards with enough extra thickness to let you mill down to the final part sizes you need. Depending on how long the final parts need to be and the actual thickness of the wood you’re buying (not all 11⁄2″ wood measures a full 11⁄2″ thick), you’ll need to allow for extra thickness for milling. Long project parts made from bowed wood, for instance, could need 1⁄2″ of extra thickness or more. The short pieces needed to build Mulder’s 13⁄8″-thick blocks, on the other hand, can be made successfully from rough wood as thin as 11⁄2″ if you’re careful.
Orient Cupped Surfaces Downward
Most boards have one concave side and edge, and these will mill best if you orient these surfaces downward during the first stages of the milling process. Concave surfaces offer two contact points and a more stable stance for the lumber as it passes across the jointer and planer beds. Convex surfaces, by contrast, are especially bad on the jointer since they encourage wobbling of wood and ever-increasing levels of inaccuracy with each successive jointer pass.
Most benchtop thickness planers use only the spinning action of the blades to eject shavings, but this setup isn’t always enough. It’s not unusual for shavings to build up around the cutterhead during heavy cuts, leading to pockmarked wood surfaces as the drive rollers press shavings down into the surrounding wood. Thus, a vacuum system is quite valuable as part of your milling setup. By extracting shavings mechanically from the planer instead of hoping they’ll just blast out completely on their own, you’re much less likely to have shavings build up in your planer, clog and cause trouble.
A dust system also keeps your shop a whole lot cleaner.
Mill in Stages
There’s no such thing as completely stable wood because lumber is always picking up and losing moisture from the surrounding air, depending on relative humidity levels. And here in Canada, the most likely stability problem you’ll face is caused by wood that’s too wet. Outdoor storage of lumber is the most common culprit. Even covered storage areas allow wood to pick up moisture that’ll lead to boards shrinking later when the wood comes inside during the heating season. To address this common scenario, give your wood time to stabilize in stages while milling. Instead of jointing and planing down to final size immediately, joint one edge and a face of each board, let the wood sit in your shop or some other heated space for three to four days, and then complete the intermediate planing.
Leave excess wood available for final milling steps in case some cupping, warping or twisting sets in. Although these changes are quite likely to happen when working with rough lumber, they are no problem as long as you allow for them.
Skill isn’t as mysterious as it looks. It’s nothing more than understanding why crucial details are important and how to put them into practice. Rough lumber is my favourite choice because it gives access to more interesting and varied woods, it costs less and it gives you creative control over thickness dimensions. Take off the training wheels and give rough lumber a try for yourself.