Internal grinding on a lathe

[Randy]

On the topic of magnets; This just appeared on YT two days ago.
World's strongest magnet. 45 Tesla.

https://www.youtube.com/watch?v=g0amdIcZt5I&t=1s&ab_channel=Veritasium

[mikey553]

Update.

I have turned a cup from a piece of junky Chinese steel I had left from the indicator stand repair. It is probably the worst steel I have ever seen. It has a crack on the OD for the full length of the bar, but it only goes 1 mm deep. You can see it at 8 o'clock. However the diameter was right and I have used it.

Made a plastic separator, turned it from a tube I had in my collection. This separator is about 1 mm thick. Could not make it any thicker from the existing material. Pressed the whole thing together and cut off the complete assembly.

Now comes a testing phase. I prepared several steel bars of different weights with machined faces. The original magnet with no modifications would lift 500 g weight. The same magnet with the cup would lift 1000 g under the same conditions. I think this is a definite proof of success. Thanks to everybody who helped with advice. I may use this magnet one day.

[BCRider]

What a great result. And of course with the extra holding power comes more friction for holding the work more strongly against cutting or grinding forces.

Did you machine on a stub arbor as well or is this just a shallow cup from available scrap since it was the right size? If it has a bit of a stub on the back you're golden for the next use!

[mikey553]

What a great result. And of course with the extra holding power comes more friction for holding the work more strongly against cutting or grinding forces.

Did you machine on a stub arbor as well or is this just a shallow cup from available scrap since it was the right size? If it has a bit of a stub on the back you're golden for the next use!

I started the cup from a piece of steel about 4" long after the separator was done and pressed on the magnet. Actually I turned the plastic tube ID, pressed in the magnet , then turned the OD and cut off. Finished the cup ID for a slight press fit and pressed the magnet with a tailstock. After that just cut off the cup to length. No stub left on the back. I can still chuck it on my lathe and use tailstock drill chuck face to push on the magnet to set it straight. I do it all the time for short parts with great success.