mini-lathe gear change for 18 TPI

R

rfresh747

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I'm trying to change my gears on my 7x12 HF mini-lathe.

I found a table showing I have to install a 40 gear in the D position...and a 45 gear in the A position: https://littlemachineshop.com/reference/change_gears.php

My factory D gear was an 80. When I install the 45 gear in place of the 80, the teeth on the 45 doesn't reach the small C gear teeth!

What am I doing wrong?
 
I just looked at the HF 7x12 manual and for 18T they say A=40, B=65, and D=45. Nothing on C. I assume D is the leadscrew gear. Download it yourself and look.
Mark
 
What thread pitch are you trying to turn? And there are two adjustments on my 7x10. Have you adjusted both of those, assuming it's the same

Sent from my SM-G935P using Tapatalk
 
ctg.co came up with:
Gear A Gear B Gear C Gear D Actual TPI
40 ANY 45 18
20 30 80 60 18
20 40 80 45 18
20 45 80 40 18
20 60 80 30 18
30 45 80 60 18
30 60 80 45 18
40 30 40 60 18
40 45 80 80 18
40 60 40 30 18
40 80 80 45 18
80 30 20 60 18
80 40 20 45 18
80 45 20 40 18
80 45 30 60 18
80 45 40 80 18
80 60 30 45 18


Gears VB6 came up with:
60 45 80 120 18
50 60 80 75 18
50 45 60 75 18
40 30 50 75 18


Gears VB6 can be downloaded here:
http://www.varmintal.com/alath.htm#Cutting_Odd_Threads

A very good change gear calculator page online:
http://www.cgtk.co.uk/metalwork/reference/changegears

If you go to the calculator page you can chose sava page as complete html page with firefox.
It will let you save the page and run it from your computer without going online.

Roy


Roy
 
Thanks everyone. I see that I needed to remove that small C gear. I didn't realize that those two gears were on a removable common mini-shaft.

So, now I've got A=40, B=65, and D=45 and nothing on C == 18 TPI.
 
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