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Posted by Richard J Kinch on May 9, 2008, 7:15 pm
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Needing an odd metric thread pitch, I finally got around to calculating
the exhaustive change-gear possibilities on the 12x36 import lathe.
Turns out that not only are there more possibilities than the few that
are tabulated in the manual, the manual gives less-than-optimal gear
choices for metric threads.
For example, a 0.75mm thread pitch, the manual specifies the 43-60-C-6
setting which results in a 1.1 percent error (off by over 0.001 inch
after just three threads), while using the "secret" 26-40-C-5 or 46-60-
C-7 settings (not given in the manual) yield a much more accurate 0.06
or 0.13 percent error. Some of these combinations like 25-40-*-* or 26-
40-*-* (using the smallest two upper change gears) may require a larger
idler gear or modifying the idler gear bracket, but even without those,
improved choices are still available.
http://www.truetex.com/hf-enco-12x36-pitch.htm
http://www.truetex.com/hf-enco-12x36-gear.htm
You can also analyze these tables to find the best compromise change-
gear choice that let you switch between a set of specific metric and
inch pitches using only the gear-levers. For example, the unlisted
47-40 change-gear combination lets me switch between 0.75mm (47-40-D-4)
and 32 tpi (47-40-D-3) with only the quick-change levers, for short
threading lengths.
The Grizzly 12x36 (G4003) supplies a different set of tooth counts (why?
just to be incompatible?) which cover the same useful pitches, but with
different combinations:
http://www.truetex.com/grizzly-12x36-pitch.htm
http://www.truetex.com/grizzly-12x36-gear.htm
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Posted by JR North on May 10, 2008, 1:35 am
Please log in for more thread options
Now to figure out which my HF 12X36 matches...
JR
Dweller in the cellar
On Fri, 09 May 2008 18:15:47 -0500, Richard J Kinch
>Needing an odd metric thread pitch, I finally got around to calculating
>the exhaustive change-gear possibilities on the 12x36 import lathe.
>Turns out that not only are there more possibilities than the few that
>are tabulated in the manual, the manual gives less-than-optimal gear
>choices for metric threads.
>
>For example, a 0.75mm thread pitch, the manual specifies the 43-60-C-6
>setting which results in a 1.1 percent error (off by over 0.001 inch
>after just three threads), while using the "secret" 26-40-C-5 or 46-60-
>C-7 settings (not given in the manual) yield a much more accurate 0.06
>or 0.13 percent error. Some of these combinations like 25-40-*-* or 26-
>40-*-* (using the smallest two upper change gears) may require a larger
>idler gear or modifying the idler gear bracket, but even without those,
>improved choices are still available.
>
>http://www.truetex.com/hf-enco-12x36-pitch.htm
>http://www.truetex.com/hf-enco-12x36-gear.htm
>
>You can also analyze these tables to find the best compromise change-
>gear choice that let you switch between a set of specific metric and
>inch pitches using only the gear-levers. For example, the unlisted
>47-40 change-gear combination lets me switch between 0.75mm (47-40-D-4)
>and 32 tpi (47-40-D-3) with only the quick-change levers, for short
>threading lengths.
>
>The Grizzly 12x36 (G4003) supplies a different set of tooth counts (why?
>just to be incompatible?) which cover the same useful pitches, but with
>different combinations:
>
>http://www.truetex.com/grizzly-12x36-pitch.htm
>http://www.truetex.com/grizzly-12x36-gear.htm
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>the exhaustive change-gear possibilities on the 12x36 import lathe.
>Turns out that not only are there more possibilities than the few that
>are tabulated in the manual, the manual gives less-than-optimal gear
>choices for metric threads.
>
>For example, a 0.75mm thread pitch, the manual specifies the 43-60-C-6
>setting which results in a 1.1 percent error (off by over 0.001 inch
>after just three threads), while using the "secret" 26-40-C-5 or 46-60-
>C-7 settings (not given in the manual) yield a much more accurate 0.06
>or 0.13 percent error. Some of these combinations like 25-40-*-* or 26-
>40-*-* (using the smallest two upper change gears) may require a larger
>idler gear or modifying the idler gear bracket, but even without those,
>improved choices are still available.
>
>http://www.truetex.com/hf-enco-12x36-pitch.htm
>http://www.truetex.com/hf-enco-12x36-gear.htm
>
>You can also analyze these tables to find the best compromise change-
>gear choice that let you switch between a set of specific metric and
>inch pitches using only the gear-levers. For example, the unlisted
>47-40 change-gear combination lets me switch between 0.75mm (47-40-D-4)
>and 32 tpi (47-40-D-3) with only the quick-change levers, for short
>threading lengths.
>
>The Grizzly 12x36 (G4003) supplies a different set of tooth counts (why?
>just to be incompatible?) which cover the same useful pitches, but with
>different combinations:
>
>http://www.truetex.com/grizzly-12x36-pitch.htm
>http://www.truetex.com/grizzly-12x36-gear.htm