Surfacing curly woods
I think that an abrasive planer might be the best choice and the easiest to find. There is a planer called Roto-plane. These cutters are vertical and cut across the board - they do an incredible job. I have a jointer with little insert cutters instead of knives. The cut is fantastic. My next purchase will be a planer with the same head.
We have this problem a good bit of the time. Both of the suggestions above are correct. There is no good way to plane curly maple with a straight knife without a certain amount of chip out. However, you can minimize it somewhat by being sure to run the lumber in both of the two possible directions; one will usually be better than the other, depending on the angle of the grain to the surface of the board.
Another idea is to run shear cutter head bodies. This breaks the cut up and will improve the cut some.
It should be noted that the tension in the wood will prevent you from getting a perfect cut all the time, so some defect is normal under the best conditions.
Dave Rankin, forum technical advisor
Curly maple and especially curly oaks are almost impossible to plane without some tear-out. A wide belt sander is the very best method to get the best results, although the slowest method as well. I have never heard of the abrasive planers before and would be interested in learning more about them.
To get by with straight knives, you can lightly wet the wood surface a couple of minutes before planing. This minimizes, but doesn't eliminate, tear-out.
From the original questioner:
Has anybody heard about or used the helical head that some of the companies like Northtech have? How do they work?
I know a number of companies here in KY that have the helix head insert knife head you are talking about from Northtech. It is an excellent system and if you are using a planer, would be my choice for a head to use. Have personally used them on curly oak, maple, birdseye maple and oak, as well as figured cherry, hickory and ash with exceptional results.
That said, if my main business was working with figured wood, I would strongly consider an abrasive surfacer, such as a Northtech, Timesaver or other. Several companies that make abrasive finish sanders make abrasive surfacers. To my knowledge these are usually single belt units, 30" to 60" in width, and designed to work with 30, 40, 60 or 80 grit belts as their primary grit size.
Using my Woodmaster 25 inch planer with a 1 degree increase in cutter knife angle at the edge of the straight knife helps reduce tear-out. Also, slowing down the power feed rate helps, as well as having dry wood. Looking at the grain direction is very important in feeding the boards into the machine. As the rotating cutter is rotating up into the wood during machining, itís best if the grain is sloping down towards the bed. Light feeding will tell you if it is tearing out the grain and then you can reverse the direction to improve the surface finish on the finish pass.
I used to specialize in running highly figured wood to pattern. I used a heavy spindle shaper or an old Belsaw. The key in both cases was "back beveling" the knives so that the angle of cut was flatter. This in turn required light passes and I would not recommend this for any hand feeding operations. It's also very loud compared to regular shaping or planing. The results were amazingly good.
Another trick is wetting the wood. Fabric softener helps, as the water penetrates better. Amway makes a product for weed sprays that is a penetrating agent.
All that said, sanding is the best for surfacing, as the results are always perfect. You can straighten a board in a planer or sander by having a "sled" underneath it. I have several pieces of 1" cabinet ply of different sizes for this purpose. You'll want a small ridge across the front of the sled so that the work piece doesn't come off. Small wedges slide between the work piece and the sled stabilizes the work piece so that it doesn't rock. It can then be fed through the surfacing machine, leaving a perfectly flat top.
I surfaced approximately 2000 feet (from many different batches) of curly maple on a 30" Whitney, with virtually no tear or chip. After grinding and jointing the knives, I could usually joint two or even three more times before grinding again. The maple planed well only if I was near the end of the cycle and there was a good size land on the knifeís edge. The knife acts more like a scraper that way. The surface is still not too nice, however, as you can feel waves in it from the different densities encountered by the knife. But it's sure a lot better than chipping.
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