Simple grinding rest.

[James Hall 3Participant @jameshall3]

That's really helpful Huub, thank you.

I hadn't appreciated that your motor was 'dremel sized' which seems fairly low powered. Do you use your set up for shaping cutters from scratch – which would be fairly slow, I guess, or just for sharpening.

[HuubParticipant @huub]

James,

The basic (non critical) shape is grinded on a bench grinder. The diamond disk is only used to (re) sharpen.

For all driven tools, when possible, i use the Dremel to prototype. If the prototype is working ok, i select the final motor.

I have a Dremel 3000 (175W). The torque is low at low RPM and the RPM is not controlled. As far as I know, the Dremel 4000 should keep the RPM constant and would be a better choice.

I try to avoid using the Dremel because it is so loud.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by James Hall 3 on 23/03/2022 10:28:14:

That's really helpful Huub, thank you.

I hadn't appreciated that your motor was 'dremel sized' …

.

Perhaps worth mentioning that NEMA 17 is so-named from being 1.7" square

MichaelG.

[James Hall 3Participant @jameshall3]

I think that I'll go for your design Huub – but with a rather heftier motor so that at least the final shaping can be done with it as well as final sharpening.

This looks as if it might be a suitable candidate – currently at a very good price and, I suspect from its intended use, with bearings sturdy enough to directly mount a disc without a further spindle.

https://www.banggood.com/Machifit-ER11-Chuck-CNC-500W-Spindle-Motor-with-52mm-Clamps-and-Power-Supply-Speed-Governor-p-1027937.html?cur_warehouse=CN&rmmds=search

[HuubParticipant @huub]

This could work and if the bearings are a problem, add some extra.

I have checked the reviews and all seems very good except this remark:

For the price this is excellent, works as intended, perfectly balanced motor. However you should know what you're doing as the power supply is a bit unsafe as there is no isolation between AC and DC side. I suggest you mount it in a grounded box sharing common ground with the potentiometer. But hey, it works and the safety concern is not in how it's constructed but the lack of instructions for novices.

If this is true, it could be really unsafe!!!!!!
This also means, there can't be a CE certification.
The CE certification on the supplied link is for a brushless DC motor and that can't be this 2 wire motor!!!!

According to the data sheet, the motor voltage is 100V DC, so be carefull.

 

Edited By Huub on 24/03/2022 22:12:39

[James Hall 3Participant @jameshall3]

Hi Huub – yes, I'd spotted that review, though even to the inexpert eye the presence of exposed 100v DC and 220v AC terminals shows that this needs a good insulated enclosure. Plainly the motor casing (plus any other exposed conducting parts) needs earth bonding.

Fortunately I have a good friend who is a professional power supply designer and can advise on safety – in view of our shared concern I probably wouldn't consider buying this without such expert advice available,

Thanks for pointing this out.

[MikeKParticipant @mikek40713]

Is it certain that banggood controller should be grounded? I have a commonly used motor controller inside the power feed of my mini-mill. There is no transformer isolation between mains and the rectified voltage, just mains Line and Neutral to the bridge diodes. It is mounted inside a plastic housing. There is no ground, which I think, is necessary, as that would create a conductive path between ground and mains because of the lack of transformer isolation. No?

(Note: I live in the US.)

Mike

[HuubParticipant @huub]

James,

You could also mount this grinding disk to a small bench grinder. On the other side you could mount a white stone for rough HSS grinding.

Huub

[Author]

Posts