Planers can be used for a variety of tasks, including routing glued hardwood paneling, thickening and veneering, and making trim. Some of these tasks can be duplicated by other machines, such as a wide belt sander or drum sander. By the time you’ve digested the contents of this article, you should have enough information to make an informed buying decision.
In the “old days” (whenever that happened), the wood was simply sawn off the logs and left to air dry. If you wanted to be able to see the grain so you could blend it with other boards, you had to plan it. If you wanted it brushed, you needed a long bed hand brush and a lot of skill. With the invention of the planer, no one needed to plan boards by hand anymore and the practice stopped in the name of “progress”. Nowadays, most boards are delivered already planed and some even have a straight edge torn, which makes things much easier for the carpenter. So why have a plane?
Thick planing does not end at the wood deposit. The wood, once the edges are glued onto the panels, is still uneven and the boards are never perfectly flush with each other. Something needs to take this rough panel from, say, 1 7/8″ to its final thickness of, say, 1 ½”, smooth both sides. There are two ways to do this that I know of: an abrasive planer (broad belt sander or drum sander) or a planer that uses blades in a cutter head.
A combination of a knife planer and an abrasive planer would be ideal, but not always affordable. This is because planers have a way of pulling chips out of loose grain. However, they remove material much faster than a sander. A sander will never remove chips, but it can consume a lot of valuable production time. So in an ideal world, where money didn’t matter, you could do most of the thickness with the planer, and then finish up to the final thickness dimension with the sander.
In fact, if you have the money and need to work wood on an industrial scale, there are machines with a planing head followed by two or more sanding heads. I had the opportunity to use such a machine for several years. A friendly competitor bought it for his woodworking business in Hawaii and shipped it from the mainland.
This giant machine, made by Cemco, used 880-volt three-phase motors. A ten HP motor powered the conveyor belt and the two planing and sanding heads had 60 HP electric motors each. It could plane and sand 52-inch-wide panels. In size, it resembled a large industrial printing house. My friend bought a sawmill and barged Hawaiian koa lumber from the Big Island to Oahu, where he had built a dehumidifying kiln next to the Cemco machine. Eventually, he overreached himself financially and had to close his business. He found a buyer for the planer/sander, but had to ship the huge machine back to the mainland because no one in Hawaii had a use for such a machine. Of course, I don’t know what his plans are for a planer, but I’m pretty sure he won’t be buying a Cemco any time soon. That still leaves many sizes and types of planers to discuss.
A planer/joker uses the same cutting head for planing as it does for joining. It looks like a jointer, but it also has a space under the jointer table where planing boards are inserted. The boards are fed in one direction on the edger table, above the cutter head, and in the opposite direction through the planer below the cutter head. This is because the cutting head only rotates in one direction of rotation. A planer, if it has the ability to shape, becomes a shaper simply by removing the straight blades and replacing them with profile cutters.
Most planers are built with the cutting head mounted on top of the machine and a metal table with rollers under the wood being planed. The thickness is adjusted by raising and lowering the table in relation to the cutting head above. The wood is driven through the machine by the front roller(s), which are usually serrated for better grip. The output rollers are at the same height as the input rollers, but are normally not driven and are shiny and smooth. There are some big expensive gliders where all the rollers work.
There are three types of cutting heads: straight, spiral and helical knife. The terms “spiral” and helical are often used interchangeably, although this is inaccurate. There are strong similarities between the spiral and helical types, but there IS a difference, as I will explain. Straight knives are used on most gliders in the less expensive range. For the most part, straight knives are fine, but they have two drawbacks: They’re hard to line up with each other after changing, and they tend to pull loose grain more easily.
Helical and spiral heads solve both problems to a great extent. It has been found that a group of small cutting blades arranged in a spiral around the cutting head will minimize chipping. Helical knives are usually square or rectangular in shape and are sharp on 2 or 4 sides. They mount directly to the face of the cutter head and therefore do not require any adjustment to align with each other. To change a cutter into a helical head, simply remove the screw that holds it in place. If there are unused edges on the cutter, you can rotate that cutter to expose the new edge to the wood, then replace the screw. You buy cutters by the box and replace them as needed – sometimes you replace just a few that have nicked. Other times, all the cutters have been dull all over the place and it’s time to replace them all.
The spiral cutter head is different from the helical head in that the spiral planer cutter head, a full row of cutters, connected together in a flexible strip, is attached to the spiral head, one row at a time. There are spiral tracks or notches in the heads that locate the cutting strips. There can be three or more tracks on a spiral cutter head. Helical cutting heads are much more common than spiral cutting heads.