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

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Can type 31 cores be cut in half ?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 5 Jul 2016 09:32:43 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>

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


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