Part 3 (1/2)

6. The new diameter or step is then trued up with a skew chisel in the same manner as a cylinder; except that in nearing the shoulder the chisel is pushed up on the cylinder until the heel, which is the only part that can be worked into the corner, becomes the cutting point. Fig.

10. In very narrow steps it will be advisable to use the heel entirely as a cutting point.

In s.p.a.ces between shoulders, too narrow to permit the use of the skew chisel, very effective work can be accomplished by slightly tipping the parting tool sideways to allow a shearing cut to be taken with the cutting edge.

7. Where several steps are required on the same cylinder, each successive one is worked out as above described.

Note:--All preliminary steps in working stock to size, laying of dimensions, etc., in preparation for the exercise in hand, will be omitted in the following exercises:

Exercise A-I--3-a. Taper Cuts

[Ill.u.s.tration: Fig. 10.]

Calipering for New Diameters. For all diameters on tapers the calipers should be set 1/16” larger than the desired measurement in order to avoid working under size in the finis.h.i.+ng cut which removes all caliper marks.

If the taper runs to the extreme end of the cylinder, as in Plate A-I--3-a, a parting tool should be used, instead of a gouge, to take off a very thin shoulder.

If the taper forms an internal angle as in Plate A-I--3-b, a gouge is used as in Step 2--Sizing Cut--Plate A-I--1-a.

In other cases where tapers connect with straight cylindrical shoulders it is best to turn the shoulders to size before working the tapers.

In cutting a long straight taper the skew chisel is used, much in the same manner as in ordinary cylinder work, except that at the start of each cut the heel must be the cutting point. This will avoid any chance of the chisel catching and drawing back and thus gouging the wood beyond the starting point. As soon as the cut is well under way the chisel may be pushed up on the cylinder so that the cutting point is a little above the heel. All cuts should be made from the highest point on the cylinder to the lowest and thus cut across the grain of the wood.

In making the cut, care should be taken to see that the chisel is not tipped to a greater angle than that of the taper wanted. Should that be done a hollow, or dished out, taper is sure to be the result instead of a straight one.

Exercise A-I--4-a. V Cutting

In cutting V's a small skew is almost always used and the cutting is done with the heel.

Place the chisel square on the tool rest so that the cutting edge is perpendicular to the axis of the cylinder. Draw the chisel back and raise the handle so that the heel is driven into the wood, thus scoring it. This cut should not be too deep or the chisel will burn. This scoring should be at the exact center of the V cut.

Swing the handle a little to the right and at the same time tip the chisel so that the grind, which forms the cutting edge, is at an angle of about 45 with the axis of the cylinder. The handle is then raised at an angle of 45 bringing the heel down to make a good cut. The chisel is then swung to the other side and a similar cut is taken. These cuts are continued, together with the center scoring, until quite close to the pencil marks. Test the angle before the finis.h.i.+ng cut is taken.

It will be found best to have the V slightly greater than 90 at the base until the final cut is made, at which time it can be trued up.

The V should be tested with the square end of a rule. The cylinder should not be in motion while testing.

When angles other than 45 are cut, the cutting edge of the chisel should be tipped so that it is parallel or nearly so to the side of the cut desired.

A-I--5-a. Concave Cuts

The concave cuts as a rule will give the pupil considerable trouble at first owing to the fact that the grind, which forms the cutting edge and which must be held perpendicular to the cylinder at the start, is on the under side of the tool and cannot be seen. However, as soon as the correct angle of the tool is located, the cut will be found as easy as any. Concaves are usually made with a medium sized gouge either the 1/2”

or 3/4”.

Place the gouge on the rest with the grind or cutting edge well above the wood. The tool is then rolled on its side so that the grind at the cutting point, which is on the lip of the gouge well below the center, is perpendicular to the axis of the cylinder. Fig. 11.

Slowly raise the handle to force the gouge into the wood. As soon as the gouge has taken hold, the tool is forced forward and upward by a slight lowering of the handle, while at the same time it is rolled back toward its first position. Care should be taken not to roll the chisel too fast or a perfect arc will not be cut.

[Ill.u.s.tration: Fig. 11.]