Now I went and did it. Let the fun begin!

[Cletus]

I'm running the above belt ratio (shown by David), Hitachi VFD at Frequency Lower Limit A062= 0.00, Frequency Upper Limit A061= 120 and realizing a range of 0 to 3716 RPM (back-gear disengaged). Of course, as expected, torque drops off considerably at the lower speeds, but this has worked just fine for me and never used any other pulley ratios or used the back-gear yet.
My "JOG" toggle switch sets A038 = 4 Jog Frequency, 4.0 Hz and this gives me 123RPM which I often use for power-tapping.

 

[davidpbest]

With the 10:1 gear reduction provided by the backgear, the spindle absolutely has more than enough torque to throw the machine completely out of tram and sheer off a 3" tap driven to the bottom of a blind hole. So lack of power or torque with the backgear engaged is a non-issue even at something like 30 Hz. With the back gear disengaged, at 30 Hz., the limitation you'll encounter with an end mill or face mill is the rigidity of the machine - not lack of power or torque. I can easily push my 935 grossly out of tram before power or torque become limiting factors. This 935 is not a 6,000 pound K&T after all.

I have a Joystick jog function on my PM-1340 that outputs a fixed frequency, but on the mill, I wanted momentary tapping push buttons specifically for tapping - see photo below (green is forward, red is reverse). This way I have the full range of speeds available for tapping which is helpful with varying materials, tap styles and diameters. In back gear at 55 RPM this mill will easily drive a 1" tapered (ever enlarging) NPT tap into 3/8" 1018.

 

[jwmelvin]

As you can see in the video, without moving the belt, I get 54-436 RPM with the backgear engaged, and 474-3780 RPM with the backgear disengaged. … Hope this helps.

That’s pretty spectacular. 8:1 range through the VFD seems great. I guess the motor is pretty well suited to it.

I will also note how wonderfully quiet your machine is, in all conditions.

An impressive setup as always. I appreciate you taking the time to demonstrate. Do I remember correctly that, for your tachometer, you use a hall-effect sensor and magnet at the spindle nose?

Thanks,
Jason

 

[davidpbest]

Do I remember correctly that, for your tachometer, you use a hall-effect sensor and magnet at the spindle nose?

Yes, four magnets actually to get more precise and quick indication of the speed at low RPM’s. Not all Tachs can be programmed to specify number of magnetic pulses per RPM, but the one I built can be. Hall effect sensor ring build is documented here.

 

[Just for fun]

Pretty Cool David, Beyond my skill set at this point, but I can see that is something I would like make someday!

Tim

 

[B2]

Impressive David! I just took the easy way out. I put 10 magnets on my spindle mounted Hall Effect system and then the inexpensive 6 digit tach display that fits in my front panel shows 10x the RPM. This way I can go very slow and get a good reading. I.e. at 1RPM the display shows 10. Mentally just shift the decimal place one over. Pictures at: Photo 10a of https://www.hobby-machinist.com/goto/post?id=882916 and more photos at https://www.hobby-machinist.com/threads/milling-nylon-backer-board.95602/

I recently also added a 6 digit counter to the same Hall sensor and so when I turn slowly I can count the number of turns/10. It also wired up simply so that with a single switch I an set it up so that it does not start counting until the proximity sensor trips. This way one can tell how many revolutions the spindle makes while the lathe is braking....i.e. how much farther does the tool travel after the proximity sensor is tripped. I.e. don't want to run the tool into the spindle chuck ..... so this determines how to set up the proximity sensor location.

 

[Just for fun]

With the 10:1 gear reduction provided by the backgear, the spindle absolutely has more than enough torque to throw the machine completely out of tram and sheer off a 3" tap driven to the bottom of a blind hole. So lack of power or torque with the backgear engaged is a non-issue even at something like 30 Hz. With the back gear disengaged, at 30 Hz., the limitation you'll encounter with an end mill or face mill is the rigidity of the machine - not lack of power or torque. I can easily push my 935 grossly out of tram before power or torque become limiting factors. This 935 is not a 6,000 pound K&T after all.

I have a Joystick jog function on my PM-1340 that outputs a fixed frequency, but on the mill, I wanted momentary tapping push buttons specifically for tapping - see photo below (green is forward, red is reverse). This way I have the full range of speeds available for tapping which is helpful with varying materials, tap styles and diameters. In back gear at 55 RPM this mill will easily drive a 1" tapered (ever enlarging) NPT tap into 3/8" 1018.


View attachment 385914

That all sounds good, I can see the E Stop, the two position brake switch, Spindle speed, and the two momentary switch's for tapping, but is the Potentiometer above the red button?

 

[davidpbest]

There are two potentiometers:

• one immediately below the RPM display marked “SPINDLE SPEED” that controls the VFD output frequency, and
• another to the right of the RPM display that can be used to tell the tach how many pulses per revolution from the Hall effect sensor, or when pressed, will alternate the tach display to SFM and allow diameter inputs.

The latter function is useful for boring and fly cutter use on the mill, but more helpful on the lathe. I have the identical tach (mounted differently) on my PM-1340GT which you can see below.

 

[davidpbest]

That all sounds good, I can see the E Stop, the two position brake switch, Spindle speed, and the two momentary switch's for tapping, but is the Potentiometer above the red button?

I should also add that the blue lighted push button in the lower left is the on/off switch for the spindle ring-light that’s built into the Hall effect sensor ring mentioned previously.

 

[Just for fun]

Very nice, Thanks for the info.

But why would you need to tell the tach how many pulses per revolution from the Hall effect sensor.