Straight Turning.

Lathe Operations
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58

good condition and carefully aligned if the turning operation is to be

accurate.

If necessary, regrind the centers and check their alignment.

When turning the workpieces, considerable heat will be generated causing the

workpiece to expand. Centers that are too tight may cause binding of the

workpiece due to this expansion.

The tailstock center or the deadcenter

must be well lubricated to prevent the workpiece from overheating.

The

center hole and the tailstock center should be lubricated before the cutting

operation with a mixture of white lead and motor oil. During the turning

operation, feel the deadcenter frequently to determine whether lubrication

or adjustment is necessary.

(3) Proper Cutter Bits For Straight Turning.

Straight turning is

accomplished with the left-hand turning cutter bit, the right-hand turning

cutter bit, or the roundnose turning cutter bit.

Wherever possible, the

right-hand turning cutter bit or a roundnose bit ground for right-to-left

turning is used and the hit is fed toward the headstock. If circumstances

demand that the bit feed from left to right, such as in turning up to a

shoulder, the left-hand cutter bit is used.

The roundnose turning cutter

bit is especially efficient for finishing cuts.

(4) Position of Cutter Bit For Straight Turning. The cutter bit should be

locked in the cutting toolholder and the holder should be fixed to the

toolpost so that the cutting edge of the bit touches the workpiece surface

at about 5 above the horizontal centerline of the piece (figure 26 on page

60) since this position gives the bit a better cutting action. The distance

above the center is governed by the diameter of the workpiece and the front

clearance angle of the cutter bit. As a general rule, the point of contact

of the cutting edge is raised 3/64 inch above the center for each