Machine Tools

2005

Update 2025

These machines have recently celebrated their 20th birthdays. Years ago they were joined in my shop by 3d printers, which relieved them of their more mundane functions. But not everything can be 3d printed.

G8689 Mini Mill

Grizzly G8689 with LMS belt drive conversion and DIY digital readouts.

Detail of DRO display.

Its companion, the G8688 7x12 lathe.

In Use

five-way bolt circles are no big deal with a digital readout.

These were some parts for Devilcat II.

History

The machines, an imported Grizzly/Sieg mini lathe and milling machine. They arrived covered in red goo and the mill table was disassembled for cleaning. many of the internal edges were sanded smooth. the goo was removed and replaced with lithium grease (leadscrews) and oil (ways).

after using the mill for a bit it quickly became apparent that it is pretty hard to cut accurately because not only do you have to do all the math mod 0.0625 but you have to remember which direction the leadscrew is pushing since there is so much backlash. a scale on each axis solves both these problems.

12" digital scale mounted on x-axis. the mounts included didn't fit; the bottom part of the mounting bracket has been replaced by a 1"x1/4" aluminum bar with the end milled flat. the readout is attached to the saddle with a brass strap bent 90.

8" digital scale on y-axis. a 6" would probably have sufficed. the mounts are reversed. again, 1"x1/16" brass is used to connect the readout to the saddle. 1+1/4" wide strap would probably work better, though, since the two holes in the back of the scale are 20mm apart.

12" vertical digital scale on z-axis. original scale mounts attached directly to the side of the existing scale with 1/4"x1" aluminum backplates. it fits perfectly under the torsion spring.
instead of bothering to find the matching connectors i just soldered wires to the contacts. i found that if the scale isn't grounded it malfunctions, so the shield is connected to the brass strap which is connected to the metal backplate of the readout.

update: only the 8" scale had the scale electrically isolated. the 12" horizontal has the scale connected to v+. (?) as such, plugging in both caused a power supply short and neither worked. fixed by connecting each of the scales to v+.

Digital Readouts

update, 2009-02-13.
Replaced digital readout electronics with new improved version. It uses one AVR to decode each channel and a fourth to poll them via i2c and update an lcd display. It would probably be possible to do it all with one avr but when you're just building one of something it's easier to just throw $10 of silicon at the problem.

This was a neat upgrade too.