Baldor Grinder Restoration

Grinder restored
Grinder restored

I received a Baldor metal grinder with 10-inch wheels, on its own pedestal floor stand, discarded from a school metal shop program. Several owners before me did not know what to do with it, mainly because the motor is wired for three-phase industrial power which is not found in U.S. residential homes. My job was to fix it up and get it working.

There were two major tasks to the restoration: cleaning/repainting, and making the three-phase motor work.

Cleaning and Painting

I started the cleaning process by removing all attachments that I could, including the wheel shroud side covers, the wheels themselves, and all electrical boxes and covers. I remove all of the old flaking paint and minor rust spots using a wire wheel brush on the electric drill. Some of the paint was still good, but much of it was stripped down to the bare metal. I could not remove the riveted-on motor label and didn’t want to paint the wheel axles, so I covered them with masking tape.

I spray painted the entire grinder and all the separate parts with primer for a good base coat. I followed it with a few coats of grey paint.

Stripping paint and rust
Stripping paint and rust
Priming parts
Priming parts
Painting parts
Painting parts
Priming body
Priming body
Painting body
Painting body


Polishing hardware
Polishing hardware

I cleaned up the hardware to make it look a little nicer. I filed and sanded the heads of the screws and bolts while spinning them in the drill press. I buffed all of them with a cloth wheel, which made them nice and shiny. I finished it with some clear spray varnish.

I reassembled all the pieces, back in the order they came off.

Painted well
Painted well
wheel reinstalled
wheel reinstalled
Shiny screws
Shiny screws


Electrical

Originally this grinder was hard-wired to the wall using “BX”-style flex conduit. There was a power relay and circuit breaker box, which engaged and disconnected all three phases in sync, using start and stop push buttons.

For the 3-phase power, I built a
static phase converter using capacitors.

I rewired the relay box to supply single phase power to the phase converter. I attached it to the pedestal stand of the grinder. I drilled holes in the pedestal and tapped screw threads into them, and screwed the relay box in place. Instead of flex conduit for the power line, I added a standard power cord. Since it uses 240 volts, double the US standard, I used a different plug and outlet.

The phase converter needs an extra momentary push button to start the motor, so I added that to the front of the grinder next to the main on-off switch.

Tapping holes
Tapping holes
Switch boxes
Switch boxes
Converter and relay boxes
Converter and relay boxes
Relay
Relay
Power to relay
Power to relay
Start button
Start button
Converter in box
Converter in box

Final assembly

The last step was to add some labels. I made labels for the various boxes and buttons on the machine, and also for the power cord and outlets. I drew them using Inkscape and printed them with my inkjet printer on glossy photo paper. I used rubber cement to glue them in place, and covered them with clear packing tape.

Labelled switches
Labelled switches
Finished, back side
Finished, back side
Finished, front
Finished, front

The final results are very satisfying, and I think this is my best restoration project yet.

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