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From: firstname.lastname@example.org (Gibbo)
Date: 15 Dec 2002 16:52:30 GMT
Organization: AOL, http://www.aol.co.uk
Subject: Re: Core gapping techniques and general SMPS magnetics stuff
Spehro Pefhany wrote:
>On 15 Dec 2002 10:33:04 GMT, the renowned email@example.com
>>The dremmel is mounted in the clamp from a rounter attatchment (which has
>>depth adjustment) bolted to the chassis.
>> | ||
>> | _______||<---Steel plate 5mm thick
>> | | ||
>> | |______\
>> | |\ <--- Grinding disc on dremmel
>> | ______| \ Poking through hole in plate
>> | | ||
>> | |_______||
>> | ||
>Very useful info, Gibbo. Any chance you could put a photo up?
>How long does it take to do a small core? Do you switch
>discs partway through to get it smoother? The commercial machines
>I've seen offered for this are big $$.
Yeah they are expensive that's why we made this. We use it about 5 times a year
and couldn't justify the expense of a commercial one.
It's not a quick process. Well.... you can do it in about 1 minute for an ETD49
but 3C85 glowing orange can't be good for it !
I did 2 ETD49 centre legs a few weeks back. Took 20 mils off (check with
engineers feeler guages against a straight edge). I use the finest disc B+Q
sell (which aren't actually made by dremmel). Keeping it cool all the time it
took around 10 mins for each one.
Don''t change discs. Rely on the core making the disc less abrasive so towards
the end of the grinding it's quite smooth.
2 points learnt the hard way.... Finish grinding before you reach your target.
I find a quick buff with a cloth and fine rubbing compound takes about 1 mil
off. If you don't do this last step you'll get inconsistent results. Presumably
due to floating magnetic particles on the end. And don't try to take off more
than about 1 mil with each pass. There's too much play in the dremmel bearings
and it tends to gouge lumps out.
I guess someone with lots of time and lots of cores to do could drastically
improve on this set up.
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