My Lathe

After thinking about it for quite a while I finally took the plunge and bought a lathe, I've always liked making things, usually it's with a soldering iron and some electronic components but now I'd like to try my hand at turning metal.
Anyway here are some of my experiences and discoveries, I hope someone finds them useful.

Thursday 15 January 2015

Threading Gears - Calculator

Whilst trawling around the net I came across a really useful utility on a Blog written by lathnovice.
Where this utility varied from the others I found was that it came at the problem from the other direction, instead of entering your gear configuration and seeing what the TPI or pitch was you could enter your gears and the pitch or TPI and it then calculated the gears you needed, the position they should go in and even the error in the pitch if you were trying to cut imperial threads on a metric leadscrew.

I purchased one of the 63 tooth gears from arceurotrade hoping to cut imperial threads on my metric lathe and this utility proves that it can be done and the error in dimensions is less than with the standard gears.

And, as usual, I thought to myself "that would really be useful as an app on my phone"

So after looking at the source code and scratching my head for a while I thought the easiest way would be to use Appinventor and create an app that just displays the code in a Web viewer so you can use it off-line.
I reduced the number of gears available and moved some of the info around so it would better fit on a phone screen.
I've checked with the creator and he's happy with this so here are some links.
The source on Appinventor Community Gallery here
The APK file here


  1. Hiya, I've had a link to your android version of this for a while on my links page but it was a bit obscure and buried so I've put a link on my main "links" menu now, too... Cheers!

    - Carl (Lathenovice)

  2. Hi I Have 4 TPI lead screw so what I Have To do for this type of lathe ratio?

  3. Dropbox link to the apk is out...

    1. Try this link: -

      If it works I'll update the original post.

  4. This comment has been removed by the author.

  5. I've downloaded it (dropbox)but I have a "parse error" when I tray to install it
    Any Idea. look like a very good app

  6. Doing great I want to make a simple home-made lathe this information will be of great help

  7. My machine is 4.5' lathe 4TPI lead screw and I want 12 mm pitch thread to be cut please send me the gear train


  8. If you have a TPI value that is not in the APK version then visit the link underneath the first image to run it in your web browser, there are more options.