Choosing a Thickness Planer

Follow this guide to evaluate the wood thickness planers on the market and select the best one for you.


| January/February 1986



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A look at the standard design of a thickness planner.


MOTHER EARTH NEWS STAFF

Though it never hurts to have a working knowledge of hand tools, the thought of dimensioning a large board with jack planes is enough to make most home woodworkers cringe. It's a fact of life that nearly all shop projects will go more smoothly if you start with straight stock of consistent thickness . . . and, fortunately, there's a power tool available that gives the hobbyist and serious woodcrafter alike the capability to custom-size boards to any dimension desired: the thickness planer.

There was a time when such a tool would have been found only in a large production shop and would have had the capacity to accommodate full-size door frames. But manufacturers with their ears to the ground have developed down-scaled machines that retain the important features of the production jobs, yet cost a fraction as much. These home-shop planers range in price from somewhere under $1,000 (complete and ready to roll) to just over $2,500, and are typically sized to accommodate foot-wide boards, give or take several inches.

Limitations of Thickness Planers

Though even a low-cost model represents quite an investment, home thickness planers do have clear-cut limitations that can only be understood by looking into the designs of the machines. Characteristically, the tool is comprised of a frame-mounted table, or bed, that's equipped with steel rollers and has the capability of being raised or lowered in fractional increments. An infeed and an outfeed roller are fixed above the table; both are power driven. A drumlike cutterhead, set between the rollers, is geared to spin at a much higher rate of speed, perhaps 4,000 or 5,000 RPM. The cutterhead is equipped with two or three adjustable knives that run the length of the drum, and a chipbreaker — usually spring-loaded — is fastened just forward of the cutterhead to both press the stock flat against the table and break the slivers cut by the rotating knives.

This arrangement is, of course, ideal for shaving wood, layer by layer, from pieces of stock, but it's not designed to remove a board's warp or cup. The reason is that, as a warped board passes into the feed roller, it gets flattened against the table in preparation for the cutterhead. After the pass is made, the stock exits from the outfeed roller, where, no longer under pressure, it's likely to spring back to its original shape . . . a bit thinner, but probably no less distorted.

Put another way, a thickness planer will make both sides of a slab of wood smooth and parallel to each other, but it won't necessarily make them straight. That task must be left to a jointer, which prepares face sides and edges by removing high spots without first flattening the board. Ideally, a jointer would be used prior to planing to guarantee one square side . . . though often at the cost of a considerable amount of stock on a badly warped board.

How to Select a Wood Planer

Surprisingly enough, all planers function in essentially the same manner. But the differences that do exist among the manufacturer's dozen or so offerings are significant enough to warrant a close inspection prior to making a purchase. Too, some machines are marketed under more than one brand name, and some distributors make their own modifications to a manufacturer's product . . . so be aware of these factors while comparative shopping.





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