Hi,

This is regarding the Harbor Freight Mini Lathe #44859
8" x 12" Benchtop Lathe

I've had my lathe for a while, and decided it was time to figure out how to cut threads. After reading the manual (not a huge help) and watching a lot of youtube videos I've figured out that you have to keep engaging the lead screw when the same number comes around (in my case 1). Then just keep advancing the 60 degree cutting tool, a small amount with each pass and the results have been acceptable so far. Cutting a relief into the bar stock where you want the threads to end seems to help immensely too.

So far so good..

(Previously I've been cutting threads using a die set that cuts a 1/4" 20NC thread suitable for engagement with the standard brass and steel nuts they sell at Home Depot.)

So... I checked the manual on how to change the gear ratios, and having figured out how to adjust the spindle offsets to accommodate different gears I thought I was almost there, BUT it seems that the gear ratios mentioned in the manual don't produce the thread (pitch?) I'm looking for.

Here is the page from the manual :

Attachment 261010

If 20NC = 20TPI then it looks like I need

B = 70T
E = 80T
D = 60T
F = 50T

So I hooked this up, ignoring C and "coaxed" all the spindles together so the gears meshed and ran smoothly.

I get a thread that seems to be significantly larger than the 20NC die.

I understand that without the TPI of the leadscrew we can't calculate the correct gear ratio and determine if I'm interpreting the manual correctly.

Does anyone own this lathe, and if so can they confirm that I'm on the right track?

Thanks,
Steve

(Additionally does anyone know that the last two setups in the table are for, is this to do with depth of cut?)