Thread: Accurate Lathe Speeds

!00 rpm would make little difference

I have one of them, not the most accurate toy, but gives you a ball park figure, especially with a variable speed lathe.

You would have to spend more than $20 on ebay to get an accurate version

I've been wanting to set up something to get a readout on my lathe. At the moment on evs I have a dial which has numbers 1 - 10 which don't equate to anything.....
I turn pens at 4, apply CA at 1 and have turned some really out of balance burl at 2......
Buggered if I actually know what speed I'm doing it all at.... Maybe I'll just get a little banger like this and make some notes (to put beside my sanding colour charts and micromesh chart....another chart)

Thanks Mick...may be the inspiration I need

Originally Posted by Pat

I have one of them, not the most accurate toy, but gives you a ball park figure, especially with a variable speed lathe.
You would have to spend more than $20 on ebay to get an accurate version

When I tested mine against an accurate frequency source from work I found it was surprisingly accurate.
If the measurement was based purely on counting the number of pulses, with a measurement time of 1 second on 360 rpm it would only count 6 +/-1 light pulses so it would have no more than +/-16% reproducibility .
However they usually measure time with a 6MHz clock and measure time using the steepest slopes as triggers in a signal output pulses so they end up having an accuracy of about +/- 1 RPM at 600 RPM and this is what I saw when comparing it to a accurate frequency source.

The most surprising thing about mine has been that I have only gone through 2 sets of batteries in the 10+ years I have owned mine and I use it a lot.