The following thread charts are provided as-is. No warrantee is made that the
information is accurate, although every effort has been made to insure accuracy.
The following charts are available. These are gear setups to cut Metric Threads
on Logan and Montgomery Wards Lathes WITHOUT a Quick Change Gearbox. These charts
SHOULD work with other Lathes that have the same ratios as the Logans. The key
factors are:
1:1 ratio from Spindle to Stud Gear
8 TPI Lead Screw
When cutting metric threads on an inch series Lathe, the half nut must NOT be
disengaged. Retract the tool and reverse the spindle at the end of the cut to return
the carriage to the start of the thread.
Please note that for MATHEMATICALLY CORRECT gearing, a 127 tooth gear must be used
somewhere in the gear train. Other ratios are provided that will have some degree of
error. Note that an error of 0.025% is approximately equal to 0.003" per FOOT
lead error.
Within each listing, there will be many different gear combinations listed. Any
one will work. Find one that uses gears you already have, when possible. Also,
some combinations may not physically fit, due to gear interference. Before ordering
any gears for a particular combination, please make sure they will fit.
You may find duplicate listings. This is due to the fact that these listings
were constructed based on the standard set of gears provided with Logan plain change
Lathes, which included duplicate 24 and 32 tooth gears. The standard set includes:
16, 18, 24(2), 32(2), 36, 40, 44, 46, 48, 52, 54, 56, 60, 64, and 72 tooth gears.
The other gears listed are the standard Metric Transposing Gears (100 & 127)
and other standard gears used for cutting metric threads with Logan Lathes. All
gears listed are available from LOGAN ACTUATOR CO.
ALWAYS check your setup carefully. We recommend taking a test cut on a piece of
scrap material.
