27 Speeds External Headstock Gearbox (Free Plans and More)

**LMMasterMariner** · Aug 24, 2018, 10:58 AM

Free plans for much better gearbox (27 speeds) can be found at

Download in pdf format will be available here soon.

W A R N I N G / W A R N I N G / W A R N I N G / W A R N I N G / W A R N I N G / W A R N I N G / W A R N I N G / W A R N I N G /
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ONE MISTAKE FOUND.

AND CORRECTED.

CHECK CORRECTIONS.pdf

DIDN'T HAVE THIS PROBLEM IN PREVIOUS VERSION (18 SPEEDS) AS THERE WERE 60 TEETH AND 64 TEETH GEARS IN THE SAME LINE
AND WITH COPY / PASTE USED IN DRAWINGS, WELL S...T HAPPENS.

Best regards
LMMasterMariner

**LMMasterMariner** · Aug 24, 2018, 12:23 PM

Here are the plans.

**olderdan** · Aug 25, 2018, 12:48 PM

Thank so much for sharing your many hours of hard work, I have saved your PDFs and even if I do not copy your design it is great start point for other projects.

**Kimbatuk** · Aug 27, 2018, 11:06 PM

Thank you so much for the plan. Just wondering if there was a 015.pdf file missing in the listing?

**LMMasterMariner** · Aug 27, 2018, 11:57 PM

Originally Posted by Kimbatuk

Thank you so much for the plan. Just wondering if there was a 015.pdf file missing in the listing?

yes, there is 015.pdf, but it is totally useless. that's why it wasn't attached. no any dimensions in it.
but there are 2 better quality plans with mm paper. 022 and 023.

**bruce.desertrat** · Aug 27, 2018, 04:23 PM

Thank you! This is a generous gift to the community.

**Frank S** · Aug 27, 2018, 07:56 PM

It took me a while to remember that your input shaft RPM is not constant Since I read your lowest ratio between shaft A and shaft D as 9 to 1 the only way I could see a 25 RPM output would have been if the input were 225 meaning there had to some additional reduction somewhere.
Is that correct?

**LMMasterMariner** · Aug 27, 2018, 09:48 PM

Originally Posted by Frank S

It took me a while to remember that your input shaft RPM is not constant Since I read your lowest ratio between shaft A and shaft D as 9 to 1 the only way I could see a 25 RPM output would have been if the input were 225 meaning there had to some additional reduction somewhere.
Is that correct?

Yes, That's correct. There is 4:1 reduction from motor to idler pulley and gearbox input speed is constant. 293.43 RPM.
One picture from the first post 'lathe external headstock gearbox' and screenshot from excel file attached. It took me some time until I came to magic number 225.