A site dedicated to CNC of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

Welcome to 7xCNC!

A site dedicated to computer numeric control (CNC) of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

The chinese made mini lathes are cheap, widely available, and capable (with a little work). They are made in a number of factories and rebadged under many names including Sieg, LMS, Micromark, Harbour Freight, Grizzly, and Homier. The basic design is common to all but details and finish do vary.

Have a look at my conversion, or see what other conversions people have done.

I've just put up an article on a spindle encoder that allows software speed sensing and CNC threading.

I'm working on some software guides (mainly for linuxcnc, as that's what I use).

Posted by  7xCNC  November 3, 2012

You can build an accurate spindle speed sensor for less than $10.

Mach3 uses a single pulse per revolution to determine speed and index for threading - this works but doesn't deal well with fluctuations in rpm (inevitable), meaning threads may not be as clean as possible.

LinuxCNC uses a spindle index (one pulse per revolution) and a spindle phase A (many pulses per revolution - I used 60). For this you need two sensors. Fortunately two optical sensors can be bought very cheaply from ebay (search for "slotted optical switch"). You can also use a quadrature encoder which uses two phases as well as an index.

It cost me US$5.88 (including shipping) for two optical sensors on PCBs with a voltage input of 3.3-12V. The main PCB has a power LED (red) and a green LED for each sensor that indicate the state - making it easy to see when it's working. My version has two trimpots that adjust the sensitivity.

I lasercut a slotted disk in 3mm MDF. The disk has 60 equal slots for spindle phase A. One of these slots is longer and is the spindle index. The disk is a push fit on the existing gear on the spindle (used for leadscrew drive on stock lathe)