Smithy Midas 1220 XL - Manual (Page 75)

For right-hand threads, start the threading tool at the right end of the workpiece and feed
it toward the headstock. For lef-hand threads, reverse the leadscrew’s rotation direction
and feed the threading tool from left to right.
With practice, you can grind cutters to almost any profile. It is difficult, however, to
sharpen such cutters without altering the cutting form, and almost every re-sharpening
requires a complete regrinding of profile and clearance angles.
After turning the work to be threaded to the outside diameter of the thread and setting
the gears for the desired thread, put a threading tool in the toolpost. Set it exactly on the
dead center of the workpiece you’ll be threading, using a center gauge as a guide.
To make sure your cutter is on dead center, place a credit card or shim between the
cutter point and workpiece (Figure 15.1). When the tool is on dead center, the card or
shim will remain vertical. With a credit card, there is no possibility of chipping the cutter
as the workpiece and cutter come together.
Figure 15.1 Check dead center with a
credit card.
Set the compound perpendicular to the line of centers and rotate it 29-1/2 degree to the
right (Figure 15.2). Place the thread gauge on the point of the threading tool and feed
the tool toward the workpiece (Figure 15.3). Adjust the tool so the edge of the gauge is
exactly parallel to the workpiece. A slip of white paper held below the gauge will help
check the parallel of the gauge to the shaft and the fit of the toolpoint in the V of the
gauge. Placing the threading tool perpendicular to the surface of the workpiece assures
a true-form thread.
Figure 15.2 With the compound perpendicular to the
line of centers, Rotate it 29 degree to the right.
Cutting Screw Threads
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