Griz G9249 (and maybe other) metric thread error

A search of the archives of this group for G9249 didn't bring up this topic, so it may possibly be "new" info that seems worth sharing. I
recently had occasion to check the metric thread table on my lathe (and in the manual) and noticed an error. That got me to wondering if I could cut some of the other common metric pitches that weren't even in the table. It's possible that the same error and omissions of possible thread pitches have propagated to other similar 12x36/37 belt- drive lathes. Anyway, here's what I found:
--The third column of the metric thread gearing, the one that shows 4.5mm thread pitch for quick-change gears set to 1A, should have a 30 tooth gear on the input shaft, as shown, but the output gear should have 40 teeth, not 32 teeth. See page 41 of the Grizzly G9249 manual.
--For this lathe, and perhaps others with similar gear setups, here are other common metric thread pitches you can cut either exactly or with very small error (probably useful for short thread engagements):
(I don't trust how text formatting will come across in Usenet. The following table should have five columns, and my intended headings for the five, in order, are: --Thread pitch, mm --Input gear (engages 127 tooth transfer gear) --Output gear (engages 120 tooth transfer gear) --Quick-change box setting --Percent error in thread pitch)
0.2     32-teeth     40-teeth     6E     exact 0.35     46-teeth     32-teeth     7E     +0.31% 0.4     32-teeth     40-teeth     6D     exact 0.7     46-teeth     32-teeth     7D     +0.31% 0.8     32-teeth     40-teeth     6C     exact 1.75     32-teeth     40-teeth     5B     -0.26% 3.5     32-teeth     40-teeth     5A     -0.26%
I have an Excel spreadsheet I used to calculate these (and basically all other possible pitches) that I'm willing to share by email.
Cheers, Tom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.