Best Tachometer for Sherline Mill

D

DeanM

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What's the best tachometer for the Sherline 5400 mill? I saw what looks like a nice one at http://www.gtronic.net, but there is no information about where it may be purchased. What do you recommend? (The Sherline DRO seems overkill since I only need the tach.)
 
I use the machtach, it can also be switched to Ft Per Min for setting the right speed for the different mills, It can either be IR or Magnetic, I switch mine between the mill and the lathe along with the motor speed control. It is a kit and will require assembly but the instructions on the site are well written.
http://www.machtach.com/home.html

IMG_20141018_175415.jpg

IMG_20141018_175415.jpg
 
+1 on the MachTach. I had three of them running on four machines - Automatically switched between the ZX-25 mill and the 9" lathe when the VFD was switched. I plan to replace them with the same when I rebuild the shop.
 
MachTach looks like a nice kit! Hawkeye, I saw a choke on their order page for machines with VFDs, did you need it?
 
Cheap VFD's generate a great deal of noise due to the PWM wave form. But this noise can be controlled with proper handling of the electrical and signal grounds. Pick a ground point usually close to the entry point of your power. Connect the green ground wire to this point on electrical chassis of the system. This point could be the ground on the VFD but that could be problematic in the long run. If you are connecting to a painted chassis scrape the paint off under the ground terminal. Connect a ground wire from the motor frame or the ground point in the motors terminal block directly to the ground on the VFD. This allows the VFD to control the noise in the motor loop. The VFD ground then goes to ground terminal on the chassis. all other grounds in the system go to the single chassis ground terminal.

This is called a star ground system. Most systems daisy chain the ground from point to point or have more than one chassis ground and this daisy chaining causes a lot of problems.

If all else fails then consider a choke but it should be the last resort.
 
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I didn't have any problems with the tachs without the choke. As mentioned above, everything was grounded to a common point.
 
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