Machinery Repairman

The following formulas will provide the information
you need for cutting V-form threads:
1. V-sharp thread
1
Pitch = n or 1 ÷ number of threads per
inch
Straight Depth of thread = 0.866 × pitch
2. American National Thread
Pitch = 1 ÷ number of threads per inch
Straight depth of external thread
= 0.64952 × pitch or 064952p
Straight depth of internal thread
= 0.541266 × pitch or 0.541266p
Width of flat at point of tool for external and
internal threads = 0.125 × pitch or 0.125p
Slant depth of external thread = 0.750
× pitch or 0.750p
Slant depth of internal thread = 0.625
× pitch or 0.625p
3. American Standard Unified
Pitch = 1 ÷ number of threads per inch
1
or n
Straight depth of external thread = 0.61343
inch × pitch or 0.61343p
Straight depth of internal thread = 0.54127
inch × pitch or 0.54127p
Width of flat at root of external thread
= 0.125 inch × pitch or 0.125p
Width of flat at crest of external thread
= 0.125 inch × pitch or 0.125p
Double height of external thread = 1.22687
inch × pitch or 1.22687p
Double height of internal thread = 1.08253
inch × pitch or 1.08253p
Slant depth of external thread = 0.708
× pitch or 0.708p
Slant depth of internal thread = 0.625
× pitch or 0.625p
6-49
NOTE: MULTIPLYING the constant by the
pitch, as in the preceding formulas, produces the same
result as if you divide the constant by the number of
threads per inch.
To produce the correct thread profile, you must
use a tool accurately ground to the correct angle and
contour. Also, you must set the cutting tool in the
correct position. Figure 6-82 shows how a tool must
be ground and set. Remember, if you are using a
Figure 6-82.—Threading tool setup for V-form threads.