ZONAL METHOD
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PITCH (MINIMUM MATERIAL) DIAMETER
Inserts "A" and "J" both
contain balls of Best Wire size, and give a reading which excludes lead error
but not angular errors. The PD. inserts can be used for both left hand and
right hand threads.
TAPER AND OVALITY
Use inserts "A" and "J" at intervals along the thread for taper, and around
the thread for ovality.
INCLUDED ANGLE
Use inserts "D" and "J". The ball in "D" is smaller than that in Pitch Diameter
insert "A", and should seat a prescribed distance deeper. If it does not,
angular error is present. The degree of error and its effect on PD can be
determined by using a formula.
UNEQUAL HALF-ANGLES
Opposite insert "J", use "E"; then either "F" or "G". "E" has full flanks,
while "F" and "G" are limited to 0.1H contact. Where half-angles are unequal
the thread groove will be tilted, and "E" will seat more shallow because its
broader contact surfaces will meet greater interference from the tilted groove.
The degree of tilt and its effect on PD. is available through thread spec.
publications.
MINOR DIAMETER
Use inserts "B" and "J".
MAJOR DIAMETER
Concentricity between major and PD is checked by using inserts "C" and "J",
and rotating the workpiece. Major Diameter size, roundness and taper are checked
by a pair of "C" inserts.
FUNCTIONAL (MAXIMUM) MATERIAL DIAMETER
Paired inserts "C' (functional) are Helically Manufactured for a single P.D./Pitch/Lead
combination. A separate pair is required for each combination. |
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SIMPLE SETTING METHOD
The MTG gage is set "between the balls" or "between the crests''. The Pitch
Diameter setting equals the nominal P.D. minus the ball radius.
All contacts (except Major Diameter) that are used opposite contact J are
marked with a constant dimension thus: + CD.0214; or -CD .0261. Setting
size is equal to the PD. setting plus or minus the constant dimension.
Paired Major Diameter inserts are set exactly to Major Diameter size. When
a single Major Diameter insert is used opposite a J insert to check concentricity,
no precise setting is required. The inserts are brought into contact with
the workpiece and the indicator is read for runout. |
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