Page 179 - Parlec Catalog

Tapping Selection

Tapping Solutions 177

Axial Feed
A thread is an inclined plane that is rolled into a cylinder. The distance between a point on the plane and the
point directly above is the pitch of the thread. To cut a good thread the tap must be fed into the work piece
precisely on pitch. This makes a tap the only tool in metalworking in which the feed rate and the speed must
be perfectly synchronized. For each revolution the tap makes it must advance the pitch. Retarding the tap’s
advance or pushing the tap will result in an incorrect thread form.

Tension Stroke
Compression The tap is a precision ground cutting tool. To allow the tap to cut
on pitch, NUMERTAP tapping attachments feature a free floating
®
tension stroke. When properly applied, the feed rate of the machine
is slightly less than the pitch. The tension stroke in the NUMERTAP ®
Pitch Tension
will allow the tap to pull itself into the work piece exactly on the
pitch of the tap. This insures that the threads will gage properly.

Torque Control
A tap in one revolution must advance the pitch. If the tap is at the bottom of the hole
or chip build-up blocks the hole and an effort is made to rotate the tool, catastrophic
failure will result. The tool will break because there is no room to advance. To prevent
this problem when tapping blind holes, select NUMERTAP units 80 and 700, featuring
®
torque control. Torque control tapping heads feature tension and compression strokes
and perform best when programmed to underfeed. Refer to programming information
in the back of this section.

Radial Float

Radial Float allows for misalignment between the machine spindle and the hole to be
tapped. It also allows the tap to follow a drilled hole, reducing tap flank rub. This is
included with all Parlec tapping heads.
Tension Only (Synchronous & Depth Control)

The NUMERTAP , 100, 200, 300, and 770 units can be purchased as tension only units.
®
(TT). Tension only is the best solution for synchronous tapping. The tension stroke will
Radial Float
.005 - .007" not affect the cycle during its normal operation but will add a safety margin for tap
elongation or spindle over-rotation. In a normal tapping cycle, tension only will improve
thread depth control by creating a positive start system.

Axial Compression
The compression stroke cushions the tap as it enters the work piece. This feature also
allows holes to be retapped. This is particularly helpful when setting up a job. The
compression stroke is adjustable from .000” to .250” to maximize depth control. Refer
to next page.

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