[zer0fighter]

Finally got my magnetic pulse sensor working and getting reliable readings within Mach3. Now I am trying to calibrate the spindle so I can do some threading on the lathe.

I have a Grizzly machine, and calculated my motor to spindle ratio to be 0.8, however it is a chinese machine so I'm not 100% sure that is accurate. My motor runs 3450rpm through a Hitachi VFD, and I'm running Mach3 through a Gecko G540 via USBCNC100.

In my Spindle Pulley setup I've chosen my theoretical top speed which is double the factory top speed where I have the belts, which is 1380x2=2760 rpm. I have set the ratio to be 0.8, so the spindle spins 80% as fast as the motor will spin. This also equals 2760rpm.

When I enter these values and plug a speed in like 700rpm, I see 680rpm. At 850 set in Mach3, I see 835. At 1000 set in Mach3, I see 990.

Can I actually calibrate this accurately without a tachometer to judge the actual speed at the motor vs actual speed at the spindle? Or is there enough data to do the math? It's late and I can't figure it out.

Thanks,
Carl

[punisher454]

are you using V belts? If so that may account for a couple % inconsistency.

[rockcliff]

One issue that comes up when you cannot get a consistent RPM reading is the index trigger slot is not wide enough, and is loosing some pulses, I have had similar issues where I have had to widen the slot, to give more time for mach to read the trigger pulse,

Also you will find when using mach lathe, for threading you will need to thread at much lower spindle speeds to get good results.

Have had a few late nights with mach lathe myself, some rest always helps.