View Full Version : VFD and speeds

10-27-2007, 08:48 PM
went and got all my wireing,switches,ect,ect,
(ready to blow myself acrost the room holding a melted screwdriver again,,,,)

How arey you guys figuring your speeds at the bit,???

do you use the VFD digital readout??

For example--
if the VFD is showing (number)
bit speed equals--?

VFD X pully setup ?
VFD - pully setup ?


10-27-2007, 09:21 PM
With my VFD, it can be set to display either Hz, RPM, or something else I don't recall offhand. The RPM value can be jiggered with a correction factor to make it correspond to one's particular machine.

For a while I had it displaying Hz, and I had a chart taped to the milling machine to relate Hz + pulley step to RPM. Then I realized that with the VFD I keep the belt on one pulley step virtually all the time, so I reset the VFD to display the RPM corresponding to that pulley step. The only time I use a different pulley step is when I want a really low RPM, and for those times I don't worry about the reading, I just set the speed to what seems right. (Which is basically what I do most of the time, anyway).

10-29-2007, 06:01 AM
I went the Hz readout & laminated chart route as even with a VFD I find it useful to use the six gears on my mill's head. 10, 20, 50 and 100 Hz seems all that's really necessary, it's easy to fill in the gaps with mental arithmetic,

Forrest Addy
10-29-2007, 12:52 PM
My VFD's display only frequency. I do a little head math (lessee 45 Hz is 3/4 of 60 Hz so 3/4 of 213 RPM is...) get the RPM. A table or a graph on the wall helps. I usually go by chip color anyway.