Blown Fuse

[Werner SchleidtParticipant @wernerschleidt45161]

The surpressing capacitors have three lines two for the mains and one for earth. this make them effectiv for surpressing. The shortage is in the capacitor direct from main to earth.

As it happen to me there was such a thunder that I could not recognize anything other special things.

Werner

[Neil WyattModerator @neilwyatt]

It would have to be very fine swarf to burn in air.

What type of lathe is it? I can't think of any machine that doesn't have a metal to metal path between tool and spindle.

[Ed DuffnerParticipant @edduffner79357]

Was the machining being done dry, without coolant or lube?

One of the forum members here has previously commented about the build up of aluminium dust on a bench sander which ignited when he later held a ferrous metal to the sander without cleaning off the aluminium dust.

I wonder what size aluminium has to be reduced to and at what temperature it becomes ignitable?

Edited By Ed Duffner on 14/08/2019 18:13:00

[Mike PooleParticipant @mikepoole82104]

Posted by Neil Wyatt on 14/08/2019 16:23:35:

It would have to be very fine swarf to burn in air.

What type of lathe is it? I can't think of any machine that doesn't have a metal to metal path between tool and spindle.

They are probably not going to turn up in the home workshop but machines have been built that run on PTFE pads, most likely there is still an earth path through the ballscrew or other equipment mounted on the table like the inductosyns etc. One thing welders were careful about was where the weld current return path was going, we did have a few occasions when the return clamp made a poor connection and the weld current fried the earths in the equipment wiring, they were also careful not to have weld current flowing through ball races as they could arc and it was goodnight to the bearings.

Mike

[KEITH BEAUMONTParticipant @keithbeaumont45476]

I have just tried to answer most of the queries, at some length, but when I went back a page to read some of the answers my new post vanished, This has happened previously and I would like to know what I am doing wrong.

The lathe is a Clarke 300M mini lathe. I have checked the earthing of every part 4 times now and am happy that all is correct. I cannot see any signs of chaffing of any of the wiring. I had been using White Spirit as a lubricant, but as this was the final polishing fine cut ,it was dry. The only swarf that was near the tool was from this pass and was very fine and lacy. The "event" happened half way across a 1 inch diameter, so the tool was already in contact with the item. No marks of the flash were left on the item.

I will, tomorrow, stop everything and take the board out and have a look underneath. I am looking for physical signs of failure, but other than a multi meter I have no means of checking whether a capacitor is half failed, as suggested.

Keith

[Neil WyattModerator @neilwyatt]

Posted by KEITH BEAUMONT on 14/08/2019 20:31:43:

I have just tried to answer most of the queries, at some length, but when I went back a page to read some of the answers my new post vanished, This has happened previously and I would like to know what I am doing wrong.

More evidence that physics doesn't work quite the same in your part of the universe, I'm afraid.

Or you may be navigating away from the page without waiting for the new posting to load?

Neil

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