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Planers and Jointers
by Jim Effner


Jim Effner

The performance of any cutting tool is the product of many criteria. There's the quality of the steel, carbide and other materials used to create the tool. There's the care and skill used in its manufacture. There's the way in which the tool is employed, and of course, there's the way it's maintained.

Assuming that you already own some knives for your planer and jointer, you'll mainly be interested in the last two categories: use and maintenance. Either your knives were precision-machined from high-quality materials or they weren't (if you bought from Jesada Tools, they were!) and either way, you want to get the best use from them. For those of you considering a purchase, I'll include some selection criteria at the end of this article.


 

Knife Operation

Installation:

There are probably as many different ways to set jointer and planer knives as there are jointers and planers, because just about every machine is designed with a slightly different system. There are some common principles you should keep in mind however:

     

  • Above all, be sure the tool is unplugged before you begin! Next, study the instructions that came with your jointer or planer. Those instructions will give you details on removing the old knives and putting the new set in place.
  • Clean any pitch, resin or other debris from the cutterhead before you put the new knives in place. Mineral spirits or similar solvents are usually adequate for the job.

     

Tip: Before placing the new knives in the tool, number the slots in the cutterhead with a pencil or marker. That way you can keep track of which knives have been adjusted or tightened.

 

  • Be sure you're installing a good set of knives. Each knife in the set must have a straight edge, and all the knives must be of the same size and weight.

 

Tip: If your reground knives have a slight nick in the edge, offset the knives a little. That way the ridge left on your stock by the nick in one knife will be cleaned off by the next knife.

 

  • The knives should project from the cutterhead the same distance. If one knife extends farther than the rest, the result will be a "one-knife finish" of very poor quality. There are a number of well-made jigs and fixtures on the market to aid and support knife alignment, but the easiest and most accurate are the "dial indicator" models.
  • The "heel" of the bevel should be about 1/16" beyond the cutterhead. Keep an eye on reground tools, as each grinding removes steel or carbide. If you find yourself unable to maintain 1/16" projection, discard the knives.

 

 

Jointer Operation:

 

  • Whenever possible, try to feed stock on the jointer so the grain points down toward you. If the grain changes direction along the edge of the board, your best bet for improving cut quality is to decrease the cutting depth.
  • Increase the useful lives of your knives by moving the fence in or out periodically. That way the full length of the cutting edge gets its share of the wear and tear.

 

 

Planer Operation:

 

  • Planers work best when they're making shallow cuts. Reducing cutting depth limits snipe and gives a cleaner cut.
  • Run stock with the grain to get a smoother finish.
  • When planing large quantities of narrow stock, feed boards at different points along the cutterhead so the knives wear evenly.
  • Plane an equal amount of each side of the board to help reduce warping.

 

Maintaining your Knives

"Touch-ups":

You'll extend the life of your HSS knives with frequent use of an oilstone hone. Jesada Tools Diamond Hone is ideal for all types of knives including carbide or carbide tipped varieties.

Regrinding:

At some point any knife requires regrinding. Each knife must be ground perfectly straight, and all the knives in the set must match. Consequently, this is an operation requiring skill and specialized equipment, and it's best left to professional sharpening services.

Selecting Replacement Knives: High Speed Steel vs. Carbide:

Most jointers and planers come equipped with HSS knives. For the jointing and planing of solid softwoods (and most hardwoods), without gluelines present, HSS works well in nearly every way. The knife material is relatively easy to sharpen by honing or regrinding.

If you joint or plane a lot of teak, plywood, particleboard or other abrasive materials, you will want to upgrade the to tungsten carbide knives (Jesada Tools carbide tipped knives that give you a cutting edge that lasts as long as solid carbide at a much lower price).

Bevel Angle:

The bevel that's ground into the knife varies among manufacturers from about 30º to 45º. A 30º angle may be adequate for some softwoods, but hardwoods require a steeper bevel (Jesada Tools uses a full 45º bevel, providing good performance in a wide range of materials).

Grinding:

If you were trying to choose between two pocketknives, you'd test the sharpness by shaving a little hair from your forearm, then you'd check the quality of the finish on the blade. Those are pretty good criteria to using when comparing jointer and planer knives as well. Is the edge straight? Is the beveled area smooth and polished? Does the appearance show attention to detail? Appearance isn't everything, but let's face it, it is really realistic to expect precise cuts from a poorly ground knife?


Copyright © 1997, Jesada Tools™.
Any reproduction in whole or in part strictly prohibited.