Boyer Schultz surface grinder electric troubles

perhaps it is wired up for 208

Try starting the grinder while the lathe motor is running. Some motors are just not happy running with a static converter. The grinder will also not run as smoothly on the static converter, which really only gets the motor spinning so it'll run on single phase.

I see a VFD or rotary converter in your future...

Ned Simmons

The so-called "static" phase converter is simply a capacitor to shift the phase of power applied to one of the three wires while the other two get the standard 220 single-phase. They are made to work with a particular range of motor horsepower, and probably are sensitive to the number of poles in the motor. A 3400 RPM motor is a two-pole (and without slip would be running at 3600 RPM). A four-pole (more common) is at some slip-determined speed below 1800 RPM (1700 or 1750), a six pole is some slip-determined speed below 1200 RPM and so on.

You may need a higher value of capacitor for a two-pole motor. Or perhaps a lower value.

But in any case, once the motor spins up to speed, the shifted power to the third phase will be automatically removed, and you will lose the benefits of three-phase power to the motor (which include full horsepower, and smoothing out of torque pulsations which can show up in the grinding finish.

Your choices for a good finish are:

1) Use the "static" phase converter to start an idler motor (some used three-phase motor of about 50% or better more horsepower than the load to be run), and add tuning capacitors to it to balance it for smooth and even power output. Don't worry if the output shaft has been damaged by a slipping pulley or by the process of removing the pulley. You don't need it at all, and can even machine it off if you so desire. (If you don't machine it off, put some kind of shield over it, so nobody can come in contact with it, for safety.) 2) Get a VFD (Variable Frequency Drive). And electronics box which takes in single phase (or three phase) and synthesizes three phase to drive whatever load. One benefit from this is that you can use it to vary the speed of the motor, by varying the frequency of the applied power. I don't think that this feature would be a benefit on the surface grinder, though it would be nice to have on the mill (or lathe). It will let you put a knob (potentiometer) within easy reach to change the speed smoothly while it is running. If the Mill (or lathe) has a step pulley, this will let you tune the speed more finely than you otherwise could. If the machine has variable speed, you can do without it, but it is nice to be able to have a knob right by the carriage on a lathe so you can vary the speed as you face off a large workpiece, so you can avoid that band of poor finish somewhere between center and OD where the speed is just wrong for the combination of workpiece material and tool material.

Note that, as someone else already suggested, you can use the existing Bridgeport spindle motor as an emergency idler motor while you are starting the surface grinder -- and probably get better finish than you would if the "static" phase converter were to actually work with the surface grinder's motor.

Note, also, that at some serious risk to you hand, it is possible to spin the wheel by hand just before switching on power and it will likely spin up, even without the phase converter. Be careful that you spin it in the right direction, or when you start to grind you may wind up unscrewing the nut retaining the wheel, which can make things rather exciting. :-)

For running multiple machines, I would suggest the rotary converter route, with someday adding a VFD to the machines which can most benefit form it. A home-built rotary converter can be very inexpensive, and once the idler is spinning, it is not really sensitive to the load motor horsepower, as long as the idler motor is large enough.

Enjoy, DoN.

P.S. I wish that my little Sanford surface grinder had a three-phase motor.

yes 3400 rpm will be a little harder to start .Start your lathe then start the grinder .When you start the lathe its now a rotary phase converter the power coming of of it is true 3 phase power.

HotDamn wrote in news:lv88905gj0j1r24pb3mq000joovv8858l2 @4ax.com:

Interesting to note, we recently had our local metalworking club meeting and we built a rotary phase converter. The first motor, an older 1725rpm motor was to be the idler, kind of groaned and spun slowly if at all. We added another electrolytic capacitor and that helped but still made a racket and spun slowly. We were at a shop with 3 phase power. We checked it and the motor ran fine. We had a 5hp 3450 rpm motor and moved the converter over to it. Fire it right up. We noticed the number of wires coming out of both. We could only surmise that the little 2hp motor must have been Delta wound instead of star wound.

Perhaps you can look at the tap chart on your Boyer-Schultz motor and tell us exactly how it reads. I bet you have the same problem. As someone suggested, if you can parallel your lathe or mill to your grinder, fire up the mill first then the grinder, let us know if it works....

Marty