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weak magnetic base

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PaulH

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#1
Got an old Brown & Sharpe magnetic base for indicators, well made and heavy, but the magnet is so weak as to be useless. Disassembled the core, made sure the on/off knob was timed correctly to the poles of the core. Then I established the existing polarity with a compass and stroked the core one direction with a strong speaker magnet. Very little improvement. So, I guess I need to "flash" the core with dc and a hand wound coil?
A difficulty arises when it is assumed that the cylindrical core 1 1/4" x 2 1/2" is polarized on the short axis. In other words, viewing the core cylinder from either end, the magnetic poles reside in the hemisphere....rather than the long axis as would be found on a common bar magnet. Thus, my question: how to wind my coil, it's shape and it's direction? And yes, I was asleep during 5th grade science class. Thanks, Paul
 

benmychree

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#2
I had to two companion magnetic tools, the vee block and the small mag. chuck, they were weak as you describe; a friend and I who had similar tools, similarly weak sent them to a vendor in the Eastern USA, who specializes in re magnetizing magnetic tools; a search on the web should turn up his contact info. Apparently it takes a lot of gauss to recharge these tools, not easy for the hobbyist. This is a reason that one should be quite cautious in buying magnetic tools on such as e bay, as I did. Description of magnetic attraction is pretty subjective and not to be trusted when spending substantial amounts of money for what looks like a nice tool, but ends up being near worthless. Before rare earth magnets became available, this diminishing strength issue was the norm.
 

PaulH

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#3
Thank you for the comeback, tried google using several parameters, no luck. This a brute of an old tool, 5/8" main stem, probably weighs 5 pounds or so, I am determined to keep it out of the scrap barrel. Maybe buy some of those Chinese rare earth magnets that are reputed to be super powerful and embed them in the body for a permanent mag base. Do you think that would cause problems on the saddle or lathe ways or mill table by holding swarf?
 

benmychree

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#4
I would not fool with retrofits; I will contact my friend who arranged the recharge and try to find out who the vendor is. That style of base is called "the doghouse", I think I have one also (too much stuff to keep track).
 

Winegrower

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#5
I have been amazed at the power of rare earth magnets, which I don't think existed back when your old holder was new. Is it possible that it's really working as designed, and we just forget how weak Alnico actually seems now?
 

BtoVin83

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#6
you might try a magneto repair shop, they recharge the magnets all the time.
 

benmychree

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PaulH

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#8
Hey fellas, thanks for the pointers. But where the hell is Nikola Tesla when you need him? The thread you referred me to told me just enough to realize I'm in way over my head. I thought I could just take a few turns of welding lead on the old Lincoln SAM 400, tape it to the magnet core and pour the coal to it. Not that simple. One knowledgeable poster correctly referred to the process as a black art. I just have this character flaw of wanting to save old Yankee iron from the scrap pile, and it's not always practical.
To add to my original query, when storing an on/off magnet, should we turn it "on" and place a keeper on it?
 

benmychree

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#9
That makes sense, the ones that I use daily, I park on the machine that I've been using.
 

Bob Korves

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#10
Got an old Brown & Sharpe magnetic base for indicators, well made and heavy, but the magnet is so weak as to be useless. Disassembled the core, made sure the on/off knob was timed correctly to the poles of the core. Then I established the existing polarity with a compass and stroked the core one direction with a strong speaker magnet. Very little improvement. So, I guess I need to "flash" the core with dc and a hand wound coil?
A difficulty arises when it is assumed that the cylindrical core 1 1/4" x 2 1/2" is polarized on the short axis. In other words, viewing the core cylinder from either end, the magnetic poles reside in the hemisphere....rather than the long axis as would be found on a common bar magnet. Thus, my question: how to wind my coil, it's shape and it's direction? And yes, I was asleep during 5th grade science class. Thanks, Paul
To avoid magnets losing their strength, they need a "keeper" to give an easy way for the flux to circulate properly, otherwise they can weaken. I try to keep all my magnets on keepers at all times they are not being used.
https://en.wikipedia.org/wiki/Magnet_keeper
 

benmychree

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#11
My friend found the info on the place that he sent our magnetic tools to:



Magnetool, Inc.
505 Elmwood, Troy, MI USA 48083
 
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