[TowerTalk] Can type 31 cores be cut in half ?

[Jim Brown]

On Tue,7/5/2016 6:58 AM, Grant Saviers wrote:
> Yes it is possible with a diamond saw in a surface grinder. However, 
> it is very messy and and the dust/slurry is very abrasive so the 
> grinder owner may say "no way".   We machined a lot of ferrite many 
> years ago for recording heads and pretty quickly the grinders were 
> trashed.
>
> You need very flat and smooth mating surfaces (see a big clamp on) as 
> this mating changes the magnetic properties of the core by inserting 
> an air gap.  Obvious it can be made to work since #31 clamp ons are 
> very effective if kept tightly closed.  A tungsten carbide blade will 
> cut ferrite in your bandsaw but I think the cut will be so rough as to 
> be useless. A diamond blade in a cut off saw may work if it last long 
> enough without water cooling.

Grant has very effectively detailed why it is a very bad idea to try 
cutting cores in half. Emphasizing, if the mating surfaces are not 
PERFECTLY smooth and parallel, there will be an air gap, and performance 
will be degraded, probably a lot.
>
> I think you need a bigger NEMA enclosure as any of these techniques 
> will cost a lot more with probably poor results. 

I can't think of a reason for using an enclosure at all. In the 9 years 
my work has been on the internet, no one has yet told me about damage of 
a choke by exposure to severe weather. Here along the Pacific coast, all 
my chokes see is a LOT of rain and sun, but I'm sure there are lots of 
ferrite chokes in parts of the world that have serious winter.  The only 
hazard I can think of is the ferrite cores cracking from freeze-thaw 
cycles.

73, Jim K9YC