Stepper Motors from China

[Dan911]

I read many threads on these but I just had a problem that I haven't read yet so I thought I'd share.

My coupler and Nema 34 R&P motor pulley's wouldn't fit on the shaft of the motors. Looking back on the specs of the motors the shafts are 13mm not 1/2 inch.

13mm = .511

I have a 17/32 bit that = .531 but concerned it might be to big. I'm hoping to find a 33/64 (.515) drill bit in a local hardware store that would be closer to 13mm.

[ger21]

Or just order a 13mm bit from McMaster Carr or Enco maybe.

[Dan911]

Originally Posted by ger21 Or just order a 13mm bit from McMaster Carr or Enco maybe.

LOL.. that would be the simplest solution.

I have today and weekend off and was really looking forward to finally start assembling the parts I been collecting over the past several months. Waiting for a bit in mail would be a setback.

Might have to though depending on my search in local hardware and tool supply stores. Checked Home depot and ace hardware last night with no luck.

Thanks for your reply,
Dan

[Dan911]

Was able to purchase a 13mm drill bit in a local mom and pop hardware store. Unfortunately that to was to small and the R&P pulley still didn't fit on the shaft.

I used a 17/64 drill bit I already had and tried tapping it on to the shaft with a hammer but soon realized that also was to tight.

I destroyed the motor pulley trying to get it back off the shaft, and once I did when I spin the shaft on the motor it's not turning as smooth as it did.

There goes the few bucks I saved buying from China.

I must add after taking the stepper motor apart to see what I could of damaged I was surprised to see NSK bearings on the front and back.

Hope there in the 3k spindle I purchased.

[ger21]

Just a note. Taking a stepper motor apart, usually ruins it. It probably won't have anywhere near the rated torque after disassembly, as it loses it's magnetism.

[Dan911]

That makes me par for the coarse here with these motors...

The really kicker is after reviewing the specs it's 13mm to the flat part of the shaft, the actual diameter is 14mm

[neilw20]

Measure twice, cut once.

[Dan911]

Originally Posted by neilw20 Measure twice, cut once.

Been a General Contractor/ Carpenter for 30+ years.

I used that line many times on employers through out the years and it is certainly called for here. Maybe I'll be a little more lenient next time.

[arizonavideo]

Originally Posted by ger21 Just a note. Taking a stepper motor apart, usually ruins it. It probably won't have anywhere near the rated torque after disassembly, as it loses it's magnetism.

I have heard this said before.

So how does the manufacturer install the rotor?

Do you know of a test somewhere or document that says that this will happen?

Thanks

Dave

[Dan911]

Unfortunately it's true. I did a search and there's a few discussions on this. Someone actually had a motor to experiment with and tested it's torque then removed shaft for 5 min and re installed and retested.

Think it lost 30% to 40% of it's torque.