Hercus lathe tachometer sensor mount

thingiverse

Mount a hall effect taco sensor to the rear gear cover which attaches to the bracket for the outer gear cover on a 9" Hercus lathe. My lathe is a craftsman version of the Hercus 9", with a slightly different headstock from the standard Hercus 9A, 9B or 9C lathes. However, I believe that the gear cover and gear cover mounts are identical on all these models. To install this sensor, simply slip it onto the top corner of the rear gear cover as shown in the photos. You can also use a threaded hole for a 3mm grub screw if needed. Initially, the fit was quite tight, so I made an additional spacer piece to sit on top of the outer gear cover bracket and space out the inner cover from the gear cover mount. The stress is removed from the fit with this addition, allowing everything to come together more smoothly without any spring tension. Note that the top edge has been cut away to allow the outer gear cover to close properly. To trigger the sensor, a rare earth magnet is glued to the bearing thrust plate. Ensure that the magnet is not too large, as it could interfere with the heads of the tumbler gear bolts and dislodge the magnet altogether. A suitable hall effect tacho can be purchased on eBay for a reasonable price.