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The photo below shows a bench grinder. If you look carefully, there are only two wires for the main winding. There's no capacitor or inductor. I also verified this using the parts diagram.

I was under the impression that a single phase induction motor cannot start on its own without a capacitor or inductor connected to a secondary winding.Induction motor

My only guess is that this motor is a shaded pole motor, but I was under the impression that they are too under powered for this application.

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    \$\begingroup\$ Lots of 1/4-HP shaded pole motors. How many nameplate HP is this one? Looks like a shading bar visible too. \$\endgroup\$ – Spehro Pefhany Oct 31 '16 at 19:42
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    \$\begingroup\$ @user148298 Sears actually once sold lathes. People don't make metal stuff at home like they used to. See the old 1960s Popular Mechanics for what an ordinary Joe sixpack could do on the weekend. \$\endgroup\$ – Spehro Pefhany Oct 31 '16 at 19:57
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    \$\begingroup\$ @SpehroPefhany Don't worry, should society suddenly collapse and practical skills be in demand, we'll have no shortage of people who can switch LEDs on and off. \$\endgroup\$ – Ian Bland Oct 31 '16 at 20:22
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    \$\begingroup\$ I it must be a shaded pole motor There is no sign of an auxiliary winding and there is something that looks like a shading bar. The grinding wheel doesn't count as load nor does the angular momentum help to start. F=MA says that no matter how small the force, there will be acceleration. The momentum will determine how long it takes for the wheel to get up to speed. As long as there is enough torque to overcome bearing friction and turn the fan, it will get up to speed. The motor torque will increase as speed increases until it reaches a peak at 3/4 speed or so. \$\endgroup\$ – Charles Cowie Oct 31 '16 at 20:58
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    \$\begingroup\$ +1, but having too much angular momentum will make the rotor heat up because of high losses at low speeds and may trip a temperature fuse. \$\endgroup\$ – Janka Oct 31 '16 at 21:05
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It's looks more like the old shaded Pole, with low starting torque that peaks before max RPM, ( no old jokes please) enter image description here

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  • \$\begingroup\$ I don't see a commutator at the OP's motor. \$\endgroup\$ – Janka Oct 31 '16 at 21:11

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