I agree that using a servo will allow rigid tapping but I'm not sure how useful that is in a lathe.  Ordinary external threading is though.  The sewing machine motors are actually "servo" motors being brushless and allowing fast acceleration/deceleration, though not maybe position control (though I'm not sure about that since basically they are synchronous).  Maybe the ideal is a dual-motor setup with 500W for fast metal removal and all-round flexibility and stepper-servo for rigid tapping?

You guys are trying to drop a V8 into a go kart.  Good as conversation starter but you're really not gaining anything.  Power plants need to be sized to fit the rest of the machine.

That massive pile of chips you see in the picture is from that equally massive .043 drill.  Face, chamfer, drill to a depth of .260. That's 6D to save you the trouble of getting out your calculator.  No coolant, no pecking, 80 parts.
I could do that all day long with a 30 watt motor.

That sewing machine motor starts so violently it has snapped a 3/8" belt, not to mention what that does to the bearings.  That's why it has that 1/8" belt, it has more stretch.

The servo motor was simply selected because it's sized correctly and is controllable without having to stand around and babysit the machine.

Hi,
well power output is not the big determinant, but smooth acceleration/deceleration is. I'm not at all sure that Mach3 applies an
acceleration/deceleration profile to its Step/Dir spindle.

Two possibilities to gain acceleration control.

If the spindle is a C axis, then it will have an acceleration/max velocity/deceleration profile per the Mach motor tuning page.

The second method relies on the servo itself. Lets say the Mach suddenly accelerates the spindle to max velocity by issuing an abrupt
stream of Step pulses, not ideal but I suspect its what might actually happen. The servo will not accelerate instantly but it will accelerate
at its maximum rate which is likely to be violent, and this is undesirable also.

I cannot speak for the little baby servo you have but the Delta servos I have, 750W's and 400W's, and Delta do 200W's and 100W's servos
in the same series, allow you to program the servo drive for the max acceleration/deceleration IRRESPECTIVE of what Mach tells it to do.
This means that the motor itself has a programmable acceleration/deceleration profile, and if I'm not mistaken the acceleration and deceleration
parameters are separate and so allow you to tailor the profile to your satisfaction.

Can you program such features into your servo?

Craig

Can you program such features into your servo?

Yes, but I'm hoping that it works in Mach3 since it's more convenient.

Fortunately, it's one of the parameters that's actually documented.

There are literally dozens of parameters that come with no explanation.
I guess you're supposed to just know this stuff.

Hi,
yes I saw that list, but nothing stood out to me that was going to do as we want. Maybe I just don't understand this manufacturers terminology.

By-and-large all AC servos work the same, and the vast majority of manufacturers have the same features. They may have different names and values but they are all there.

Some of the cheaper Chinese brands have poor documentation, and I'm sorry to say but this looks like an example. Having said that, those parameters which are listed and explained
should give an absolutely superb servo, certainly better than any stepper you've ever encountered, and at a fantastic price. Every once an a while you need to dive deep into the servo
programming and that's where the lack of documentation really hurts.

Delta is a Taiwanese brand but manufactured in China. The documentation is very good indeed, and the set-up and tuning software is better again. Delta are not the cheapest brand,
but they are a lot cheaper than any US, Japanese or European brand, with comparable quality, documentation, set-up and tuning software and support. With Delta servos, with which I am
most familiar, I can certainly program an acceleration/deceleration profile. The other servo for which I have some experience is Allen Bradley, and with that servo too I can program an
acceleration/deceleration profile.

I think you need to work out how to get Mach/ESS/BoB to produce the required Step/Dir signals to get the servo to run. Depending on how Mach3 applies, or does not apply, a profile,
then you may have to dive into servo tuning. You might also want to consider the C axis solution.

I use Mach4 and have done for seven years, its light years ahead of Mach3 IMHO. Mach4 has six OB (Out of Band) axes, which can be jogged, and which still have a motor acceleration/deceleration
profile as part of the motor tuning. A continuous 'Velocity Jog' would give you a smoothly accelerating/decelerating spindle. Whether you can do the same in Mach3 is questionable.

Craig

Worth looking at this video.
https://www.youtube.com/watch?v=hi09g49JksA
These sewing machine motors are fantastically controllable, they would be great for machine tools with a bit of understanding of how to use them.  They usually have a foot control for the machine operator.  This thread has some interesting information.
https://www.model-engineer.co.uk/forums/postings.asp?th=171903&p=2
The fact that the controller may not be mains isolated isn't a show stopper - lots of DC motor controllers on CNC mills aren't either!

Well, I'm a happy camper.
 
I finally got time to give it some serious attention and it's now running just the way it should. Smooth and silent from 30 to 3000. I didn't try going over the design rpm but I'm sure it would.
Right out of the box the acceleration and deceleration seem quite acceptable.  Once it actually is moving the spindle rather than just sitting on the floor it will be easier to tune it in.

The gory details:  My first problem turned out to be the way I had been checking for a signal. My VOM has a frequency function and I had been using that.  I finally realized the computer doesn't push a signal out, it offers it up.  If the motor isn't accepting the signal, no sinking occurs and there is nothing for the VOM to read.  Once I realized that, I went back and took a much closer look at my setup.  I had plugged the motor into the wrong power supply so it was not getting adequate voltage.  So much for doing things according to memory.  Once it had the proper supply, things got turning and from then on, it was just a matter of sorting out the settings to get it spot on.

Now I finally feel comfortable with ordering the rest of the stuff needed to complete the installation.