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Skew Planing

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Skew Planing

By Alan Lacer


The skew is one of the most useful tools in the turner’s arsenal. This article will get you on the right path towards mastering this tricky but useful tool . A lot of us start out trying the skew without a clue as to how it is used. The result is often a nasty dig-in that leads most people to retire their skew to a drawer someplace. There, the secrets and abilities of the skew lay dormant and undiscovered. It’s not a surprising phenomenon because the skew has a steep learning curve with lots of subtlety. To add to the problem, there’s just not much instruction around on how to use the skew.

I have been teaching students how to master the skew for decades. I always start with skew planing as the fundamental skew cut. Once you master this cut, you will be well on your way to confident use of the tool. I’ll first show you how to practice the cut. Plan on working a number of practice pieces before tackling actual projects. In future articles we will build on that foundation and look at other more advanced skew cuts.

 

Applications

The number one application for the planing cut is spindle work where the grain of the wood is parallel to the bed of the lathe. Planing cuts are used to create cylinders, tapers and shallow concave or convex cuts. After practice with planing cuts, I encourage my students to make their own tool handles using a skew (Photo 1). It’s a great first project to hone your new skew planing skills.

 

The right skew

A wide skew is best for planing cuts (Photo 2). It’s extremely important that the skew be very sharp. The degree of control with this tool is in direct proportion to the degree of sharpness. Be sure that the corners behind the cutting edge are softened or rounded over all the way back to the ferrule. This allows the tool to glide on those corners with a smooth motion across the tool rest.

The modified grind that I favor (curved edge for the lower two-thirds, straight across for the upper third) has one huge advantage for the planing cut: if you maintain the cut in the curved section you will almost always avoid a dig-in. Also, a curved edge cuts cleaner in woods that tend to chip.

 

Prepare the lathe

The next step is to prepare the lathe itself. I strongly recommend using a cup drive rather than the spur center that came with your lathe (Photo 3). Finally, check the tool rest and file out any nicks or dents with a mill file. Finish prepping the tool rest by rubbing on a little paraffin wax. Now your skew can glide effortlessly across the rest as it cuts.

 

Practice makes perfect

Start with a 2” x 2” x 8”. square blank mounted between centers. I suggest a softer wood like yellow poplar or red alder that’s straight grained and free of knots. Cut up 2 x 4’s will do in a pinch. Just be sure to cut out the knots.

Always wear a full faceshield. With the lathe set to a moderate speed (900 to 1400 rpm) use a spindle-roughing gouge to create a cylinder. In time you will enjoy roughing short pieces like this by planing with the skew.

Start your practice cuts with the skew at the right end of the cylinder (Photo 4). Slowly advance the tool to the left until you reach the edge of the wood. Turn off the lathe and admire the quality of the cut surface. Develop your skill by cutting both directions on the cylinder (Photo 5). Also, be sure to always cut “downhill” (larger to smaller diameters) when there is a variation in diameter.

 

Typical problems with planing cuts

Dig-ins: This is perhaps the most feared problem as it does considerable damage to the wood and to your nerves. A dramatic digin often causes new turners to reject the skew as having a mind of its own and a vicious one at that. As a consequence they miss out on all the skew has to offer the serious turner. To avoid dig-ins, use a large skew and stay within the lower twothirds of the edge (Photo 6). Even if you cut with the short point or leading edge of the skew, it won’t dig-in (Photo 7). A dig-in always happens when the unsupported portion of the tool (the long point or trailing edge) is pulled into the wood (Photo 8).

Run-backs: Run-back, aka screw threading or spiraling, is one of the most common problems students have when learning to plane with the skew (Photo 9). The cause is simple but subtle: loss of bevel support below the cutting edge. It can occur at anytime: when you first contact the wood, midway in a cut or at the conclusion of the cut. The solution is to keep the bevel in contact with the wood at all times.

Chipping: Just like using a hand plane or running a board over a jointer, chipping or tear-out can be a significant problem when planing with a skew. Some woods are naturally more “chippy” –such as red oak or figured woods. Borrow techniques from the hand plane user: change direction and “skew” the skew chisel by moving it from a 45 degree angle to the axis of the lathe to 60 or 75 degrees. Anyone who has used a jointer knows that a slow feed rate reduces chipping. In highly figured woods I sometimes advance the tool at a crawl— but end with little or no chip out.

Ribbing: When you hear an odd humming noise and notice the wood has a corrugated or washboard appearance, you have encountered “ribbing.” Slight ribbing is not considered a major flaw and can be sanded away easily. Deep ribbing is a major flaw that often happens on long narrow stock. Usually the cause can be traced to the tool bouncing in and out of the cut or the wood flexing. A dull tool contributes to both causes, so keep the skew sharp. To steady the flexing wood, many professionals use a hand on the backside of the wood (Photo 11). If you are not comfortable with this approach, try an overhand grip while applying downward pressure to the tool rest (Photo 12). Remember – practice makes perfect.



This story originally appeared in American Woodworker January 2008, issue #133.

January 2008, issue #133

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1. I prefer a large 1-1/2in. or 1-in. skew for planing. The modified grind on the large skew makes the tool easier to use.


2. Replace your headstock’s spur drive with a cup drive. A catch is ineviable when you’re learning. A cup drive slips like a clutch to minimize a catch; a spur drive holds fast to the wood and aggravates a catch.


3. Start your practice cuts about 1-in. from the cylinder’s right end. Cut with the tool’s lower half, or short point, leading the cut. Rest the skew on one of its rounded corners—not flat on the tool rest. Rub the bevel on the cylinder, then gently lift the handle until the edge cuts into the wood without losing contact with the bevel. Slowly advance the tool to the left.


4. Practice planing in the opposite direction. Reverse your hands or shift your body around. Experiment with your front hand either below or on top of the tool.



Typical problems and how to avoid them

Avoid dig-ins

5. A dig-in can be dramatic, especially when using a spur drive on dry hardwood. You’ll get a dig-in if the unsupported trailing edge or long point of the tool catches and is pulled down into the wood.


6. Avoid dig-ins by using the lower 2/3 of your tool, starting just above the short point. Stay away from the red zone indicated above.


7. The short point can safely enter the cut because it is supporteed by the tool rest. It’s sometimes used to cut up to a detail although it tends to fray the fibers a bit.


Eliminate run-back

8. Run-backs are caused by a loss of bevel support below the cutting edge. The solution is to feel the bevel contact the wood before the cut is made. Then, maintain that feel throughout the cut.


Minimize chipping

9. Chips are a serious flaw that requires major sanding to fix. To avoid chipping, steepen the cutting angle for more of a shearing cut and slow the feed rate. Also, be sure to use a sharp tool.


Reduce ribbing

10. Ribbing is a series of ridges caused by vibrating stock . To dampen vibration, support the stock with your hand. Set the tool rest close to the work and use your thumb to press down on the tool.


11. If you are uncomfortable with backing the wood with your hand, try to keep firm downward pressure on the tool. This helps to eliminate ribbing from a bouncing tool.