Re: Cutting torroidal cores

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Ben,

I've cut a 30A and 20A variac some years ago. I used a gravity band saw
(kind of a hands free method except for beginning and end). It worked
fine, but took a good 20 or 30 minutes to  get through them. One was a
solid composite core, the other was laminations. The solid core was
obviously easy. The laminations required me to clamp each side prior to
cutting to prevent the laminations from expanding. I would suggest using
a similar technique except you will need a few manly-sized vice grips.
Just ensure your clamped on each side of your cut mark. Once one cut is
made, do the same with the other cut.

You could also drill a bolt hole through the core prior to cutting to
secure (probably 6 holes or 2 each top and bottom - center, right, left
sides). When cutting, core filings will find thier way between
laminations and will expand the laminations some in the area cut.
Difficult to get rid of this happening without an extremely tight clamp
design around all perimeters.

No matter how you slice it (pun intended), it does take time, patience,
and preferably in a machine shop with all the goodly tools. May make
sense just to take it into a machine shop and let them do it.

Take care,
Bart

Tesla list wrote:

 > Original poster: "Ben McMillen by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <spoonman534-at-yahoo-dot-com>
 >
 > Hi all,
 >   Does anyone have any suggestions on how I might go about
 > cutting a 1/2" wide slot in a torridal core? (the kind that
 > you find in variacs) I need to cut a slot all the way
 > through to make a "c" core so that a metal disc can pass
 > between the poles. The cores are made from soft iron strap
 > that's been coiled. They've also got plastic formers around
 > the inside and outside. I've heard mention that they tend
 > to come apart when cut... Is there any way to prevent this?
 > I've got access to a really good machine shop..
 >
 > Thanks for any help!
 >
 > Coiling In Pittsburgh
 > Ben McMillen
 >
 >
 >