SUMMER 2018

176
THE DISTRIBUTOR’S LINK
LARRY BOROWSKI 6e AND 6E PITCH DIAMETER ALLOWANCES PROVIDE SPACE FOR HEAVY COATINGS from page 158
In an effort to make the use of the”6E” and
“6e” thread classes easier for manufacturing
“before coating” threads with greater
allowance I have compiled the tables for those
thread classes (right).
ASME B1.13M does however contain
tables for the “E” and “e” allowances, where
additional sizes not shown in the tables above
can be easily calculated. Table 12 shows the
“6” positional tolerance, Table 13 shows the
external thread “e” allowance, and Appendix F
shows the internal thread “E” allowance. The
easiest way to achieve the correct calculation
is to simply add or subtract the “e” or “E”
allowances from the standard 6g or 6H PD
sizes. A more fundamental approach using
internal threads as an example would be
to start with your basic size and add the
“E” allowance. This becomes your “LO” or
Go pitch diameter. Then you add your “6”
allowance to the LO PD to get your “HI” or
NoGo pitch diameter. External threads work
the same way, only you subtract your “e”
allowance rather than add.
Similar values can be found in ISO 965/1,
Section 13.4.2, however a 1.32 multiplier
is utilized for grade 6 which calculates
out to slightly different values, less than
.002mm difference which can be considered
insignificant.
The final acceptance of threads after
coating should be determined by using 6H
GO plug gages for internal threads and 6h GO
ring gages for external threads. The use of
these class gages for final thread acceptance
assures that thread interference will not occur
during product assembly.
LARRY BOROWSKI | GREENSLADE & COMPANY INC