Skew chisel (woodturning)
From WikiWOOD
This article is about the use of the skew chisel in woodturning. For other uses of the term, see skew chisel.
The skew chisel is used primarily in spindle turning.
Contents |
Description of skew chisel
The skew is sharpened at a quite acute angle, something like 20 degrees is typical. This creates quite a 'long' bevel. The cutting edge is typically skewed at an angle of about 70 degrees. The extreme ends of the cutting edge are referred to as the short point and the long point. The part of the bevel furthest from the cutting edge is referred to as the heel.
Using the skew chisel
There are three distinct ways to cut with the skew chisel.
- Cut with the long point. Normally used for making V cuts and cutting across end grain.
- Cut with the edge. Used for making planing cuts and beads.
- Cut with the short point. For making a chamfer or as an alternative method of cutting beads.
Facing cut
This cut is made across endgrain with the long point of the skew. It can be made perpendicular to the lathe axis as shown in the photo, or at slight angle as in the video.
Only the long point engages the wood. The tool is guided by the bottom edge of the bevel; the tool is held such that this bottom edge of the bevel is pointing in the direction the cut is required to go.
The cutting edge and bevel face are angled slightly away from the wood to ensure that the cut stays solely at the long point. If the cutting edge is allowed to engage the wood, the sudden force on the tool will make it uncontrollable and a catch is inevitable.
 Facing cut |
 The long point does the cutting while the rest of the cutting edge is angled safely away from the wood. |
 From the turner's perspective you can see that the bottom edge of the bevel rubs the freshly cut face of the wood. |
Chamfer cut
This is similar to the facing cut, but because it is at a less steep angle, the short point of the skew chisel is preferred. The chamfer may be a finished feature of the turning, or it may just be a step in roughing out a large bead.
The cut is made on the short point of the skew, and this throws out a curf in front of the cut, creating a pocket which helps to control the cut, stopping the skew from leaping forward. The skew chisel is oriented such that the bevel is pointing in the direction you want the cut to proceed. The bevel face and the cutting edge are kept just clear of the chamfer surface. The bevel 'rub' which controls the tool is made at the intersection between the bevel face and the bottom edge of the tool.
 Chamfer cut |
 Chamfer cut |
Planing Cut
The skew excels at the Planing Cut. After a spindle is roughed to a cylinder, the skew can be used to plane the surface, resulting in a very clean cut.
You may direct the planing cut in either direction. Start with the skew on the tool rest with the long point up and the cutting edge tangent to the surface, slightly above center. Raise the handle until the bevel touches the wood, then raise slightly more to engage the cutting edge. (Some turners describe this as turning your wrist to engage the cutting edge.) The edge should cut the cylinder slightly below the center of the edge. Now move the skew along the cylinder. The resulting cut will peel a small long shaving from the wood.
Be-careful not to move the cutting edge towards the long point. You may end up the cut by moving the cutting edge up towards the short point.
Cutting beads with the skew chisel
Standing in the right place before starting to roll a bead is very important. Before you turn the lathe on, make a few pretend cuts, making sure that you can comfortably move the tool from its starting position with the bevel parallel to the lathe axis, to its finishing position with the tool handle perpendicular to the lathe axis. A common problem for novices is to stand in a comfortable position to start the cut, but then quickly find they are off balance by the time the skew is cutting into endgrain. It is at this point that the wood requires more force to cut, and the turner looses control.
Wrist action is important too. You need to be able to roll the tool comfortably through 90 degrees. Hold the tool handle with the thumb along the handle and in line with the top of the blade. I find this puts my hand in a comfortable and controlled position throughout the cut.
Another common problem is trying to cut beads which are too small. The problem here is that the skew still needs to swing and rotate through the same wide arc, but on a small bead it has to do so over very little forward movement. This requires considerable coordination. It is a good idea for novices to start on beads about 1 inch diameter, and certainly between 1/2" and 1 1/2" diameter. Practice in softwood to begin with where the forces involved are less. I find 2x4 spruce studs to be good, ripped up into square stock and only using pieces that are straight grained and knot free.
Beware of anything that suddenly changes the forces on the cutting edge. Most common is letting the cut move from the cutting edge to the point. While a bead can be cut in either position, the way the cut is made and the forces on the tool are quite different. Switching from one to the other part way through a cut is a recipe for disaster, though it can be done with care. Other common problems like this are allowing the depth of cut to get too big, or not being ready for the extra force required to cut through the endgrain.
If you loose the cut part way through a bead, take care. Do not drag the cutting edge back up the cut surface as this will cause a catch if the edge contacts the wood without bevel support. Until you are very familiar with the tool, it is a good idea to consciously remove the tool from the wood, then rub the bevel and carefully reintroduce the cutting edge just behind where you left off. If at anytime the cutting edge contacts the wood without bevel support or the turner having full control of the tool, then a catch is almost certain.
| Image:40px-Pencil-n-Paper.png | Please help improve this article by expanding it. Please read the discussion page for more details and improve this article if you can. |
| Image:40px-Camera.png | It is requested that a photograph(s) be included in this article to improve its quality. Please read the discussion page for more details and improve this article if you can. |
