I'm wondering if anyone have installed spindle speed control on their Sherline mill. I've tried to find information on this with Google, but there isn't too much relevant info to find it seems. (I might use the wrong search term though)
I'm hoping to control the spindle speed from EMC, and I guess it shouldn't be that difficult compared to some of the achievements shown on this forum...
The closest thing I've found is the DigiSpeed from Homann Designs, but no pictures of a install on a Sherline or user feedback.
It is pretty straightforward - you can get that board or similar, I know www.cnc4pc.com has one too.
Basically, if you have speed controlled by a knob currently (a turnpot adjusting voltage to the built-in controller), you can instead hook up an interface board like you have looked at which simply takes a signal from Mach and turns it into a 0-5v or 0-10v output. In this way the built-in speed controller sees the same input as it would normally get from the turnpot and doesn't know you aren't actually just fiddling with the original knob.
It is a neat option, but one I find in practice is not all that useful for me very often, your work may be different. I always use M3 and M5 (spindle start and stop), but I usually don't often need to change speeds mid-cut, so on-the-fly speed changes during a cut just don't come in handy that horribly often. I just use the knob.
What does come in really handy is just a relay to turn the spindle on at the beginning of a cut and stop it at the end so I don't come back to a finished cut where the spindle has just been running on for an extra hour after the cut was finished.
A simple relay that allows the use of M3 and M5 commands is really cheap and simple to do, they are like 5 bucks. Then again, full speed control isn't that difficult or expensive either, so why not? Depends on your budget and how often you plan to program speed changes into your code.