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Re: Get your kicks (out of) polishing toroids



I get this problem all the time when using a belt sander to clean up the
ends of parts that have been cut with the bandsaw. Now I know to either
keep one hand touching the sander's chassis, or keep the workpiece in
contact. I suppose an anti-static grounding strap (with the 1 meg resistor)
would also work. Or, I could work barefoot...

Still get bit occasionally, though. Not only is the workpiece the
capacitor, but so are you, and your C is probably much higher than that of
the work piece.

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> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Get your kicks (out of) polishing toroids
> Date: Monday, March 08, 1999 9:19 PM
> 
> Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> 
> 
> Hello All,
> 
> Today I had a rather interesting experience. I had just finished
> soldering my corona shield together. I built this out of 3/4"
> soft copper (hard as heck to bend into a 15" perfect circle)
> and some 9/16" hard copper for the spokes. It looks like a
> marine type steering wheel. After filing away the excess
> solder, I decided to polish it to remove sharp edges that
> might lead to corona (okay, okay, Iīm a stickler for good
> looks!!). So I stuck a buffing wheel into my Walker-Turner
> drill press and started polishing away. After a few seconds
> of polishing I accidently got my head near the drill press
> top (steel case) and got ZAPPED!!. Believe me, I sure was
> surprised. I immediately stopped polishing and stopped the
> drill.  I kept hoping "Please not the drill press" (being
> defective, I mean) Anyway, I whipped out my DMM and
> started measuring. Nothing!! Everything was normal. I
> couldnīt have believed it anyway, since my shop is fused
> and has a ground (and neutral) fault interrupter that kicks
> out if >30mA flow, where they shouldnīt. So I started
> polishing again and..... yep, the same thing happend (only
> this time it was my finger, which wasnīt as "surprising" as
> to my forehead. I could repeat this at will. Very amusing
> (once you get used to it). What happend? Well, during the
> polishing action I was charging my 10pF cap (the corona
> shield). The longest spark I got was about 5/8" long.
> Interestingly enough the charge would "stay around" for
> at least 10 seconds. The second interesting thing was it
> wasnīt even a super dry day (air humidty was ~35%).
> So, even though I usually hate polishing things (lots of
> work!!) I really got a kick out of it (sorry, but I COULD
> NOT resist that pun) this time.
> 
> 
> Coiler greets from germany,
> Reinhard
> 
> 
> 
> 
>