How to Use a Wood Planer

Published: 19th April 2010
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In the "old days" (whenever that was) planks were simply sawn out of logs and left to air dry. If you wanted to be able to look at the grain so that it could be matched with other wood, it had to be planed. If you wanted it surfaced, you used a long bed hand plane and a lot of expertise. With the advent of the planer, no one had to plane boards by hand any more and the practice ceased in the name of "improvement." Today, most boards are brought to market already thickness planed and some are even straight line ripped on one edge, making things very easy for the woodworker. So, why acquire a planer?

Thickness planing does not conclude at the lumber yard. Boards, once edge glued into panels are still uneven: The boards are never in perfect alignment with each other. Something must take this uneven panel from, say, 1 7/8 down to its final thickness of , say, 1 1/2", smooth both sides. There are two ways of doing this that I am aware of: an abrasive planer (wide-belt sander or drum sander) or a planer that uses knives in a cutterhead.

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. They are, however, much faster in removing material than a sander. A sander will never tear out chips but it may use a lot of valuable production time. So, in an ideal world, where dollars didn't matter, you could do most of the thicknessing with the planer and then finish up to the final thickness dimension with the sanding machine.

In fact, if you have the dollars and need to do your woodworking on an huge scale, there are wide belt sanders with a planer head followed by two or more sanding heads. I had the chance to use such a machine for several years. A friendly competitor bought it for his woodworking firm in Hawaii and had it shipped in by ocean freight from the mainland.

This giant machine, made by Cemco, used 880 volt, 3 phase motors. A ten HP motor ran the conveyor belt and the one planing and two sanding heads each had 60 HP electric motors. It could plane and sand panels 52 inches wide. In size, it looked like a large, industrial printing press. My friend bought into a sawmill and had Hawaiian Koa wood shipped by barge from the Big Island to Oahu where he had constructed a dehumidification kiln next to the Cemco machine. Eventually, he over-extended himself financially and had to close his business. He found a buyer for the planer/sander but he had to send the huge machine all the way back to the mainland because no one in Hawaii had a use for such a gigantic planer/sander. Of course, I don't know what your plans are for a planer but I'm pretty sure you won't be buying a Cemco any time soon. That still leaves a lot of sizes and types of planers to take a look at.

A planer/jointer uses the same cutterhead for planing as it does for jointing. It looks like a jointer but it also has a space underneath the jointer table where you pop in boards for planing. You feed the boards in one direction on the jointer table, above the cutterhead, and in the opposite direction through the planer underneath the cutterhead. This is because the cutterhead only spins in one direction. A planer, if it has molding capability becomes a molder simply by detaching the straight knives and replacing them with profile cutters.

Most planers are made with the cutterhead mounted in the top part of the machine and a metal table with rollers underneath the lumber being planed. The thickness is adjusted by raising and lowering the table with relationship to the cutterhead above. The lumber is driven through the machine by the front roller or rollers which are usually serrated for better grip. The outfeed rollers are at the same height as the infeed rollers but they are usually not powered and are shiny and smooth. There are some large, pricey planers in which all rollers are powered.

There are three types of cutterheads: Straight knife, spiral and helical. 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 planers in the less expensive range. For the most part, straight knives are fine but they do have two drawbacks: They are difficult to align with each other after changing and they tend to tear out loose grain more easily.

Helical and spiral heads get around both problems to a large degree. It has been found that a large number of small cutter blades arrayed in a spiral wrap around the cutterhead will minimize splintering. Helical knives are usually square or rectangular in shape and sharpened on either 2 or 4 sides. They are mounted directly onto the face of the cutterhead and, thus, require no adjustment to align them with each other. To change a cutter in a helical head, you only have to 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 board and then put back the screw. You buy cutters by the box and replace them as needed: Sometime you replace just a few of them that have become nicked. At other times, all cutters have been dulled on all sides and it is time to replace them all.

The spiral cutterhead is different from the helical head in that in the case of the spiral planer cutterhead, a whole row of cutters, connected together in a flexible strip are attached to the spiral head, one row at a time. There are spiral tracks or indentations in the heads that locate the cutter strips. There may be three or so tracks on a spiral cutterhead. Helical cutterheads are much more common than spiral heads.



Bob Gillespie


© 2010 Robert M. Gillespie, Jr.

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