# Standard Vs Fine Pole Permanent Mag Chuck



## maker of things (May 6, 2016)

I have been researching a mag chuck for my grinder.  I get that fine pole chucks are better for small or thin parts, the info I have not been to find is what is considered a "small part" that would make better use of the fine poles. I don't plan to do thin parts.


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## JimDawson (May 6, 2016)

I have used ( and own ) both, I would go for the fine pole.  Fine pole chucks seem to hold everything better, doesn't matter how big the part is.


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## Bob Korves (May 6, 2016)

I have seen fine pole adapter plates that go on top of wider pole chucks.  The wider pole chucks are purported to have more holding power, at least with bigger parts.  Perhaps an adapter plate can give you the best of both worlds, at the acquisition cost of the adapter plate, the extra thickness (~1/2-3/4"?), and maybe compromising accuracy a bit with it installed.  I have no experience with these, just laying it out there as an idea.  Maybe someone else here knows about them.


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## maker of things (May 6, 2016)

what are the odds that a used one on ebay would be any better than a new chinese one?  I have read about issues with old/disused chucks being difficult to operate and I would imagine if left in the off position could have developed rust on mild steel poles inside?


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## intjonmiller (May 8, 2016)

It's a matter of the shape and size of the magnetic fields. With a standard/wide spaced magnetic chuck the magnetic fields extend well above the top of the chuck surface. Large loops. With a fine magnetic chuck they do not extend very far above the surface, so only very small parts are really "encompassed" by the fields. In most situations large parts are held just fine by fine pole chucks, according to my reading (with zero actual experience with a fine pole chuck, and minimal with a standard; just relaying the theory), because the parts are solid and therefore holding the bottom is sufficient. But based on my understanding of magnetic fields, magnetic chucks, and leverage, I wouldn't want to use a fine pole chuck on a part near the vertical capacity of my grinder. 

If you have the budget for it, I recently saw that Suburban Tool at least used to make one that had alternating coarse and fine poles. I believe Tom Lipton showed it (used) in a video on his Oxtool YouTube channel. That strikes me as an ideal design.


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## Andre (May 8, 2016)

When grinding small parts, regardless of pole size it's a good idea to "block them in" with larger pieces of steel to keep the from moving around. Or clamp them in a grinding/toolmakers vise.


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## gi_984 (May 17, 2016)

> block them in" with larger pieces of steel to keep the from moving around. Or clamp them in a grinding/toolmakers vise.



This is the way I was taught.  Seen more than one part launched off the table at the tech school.  There is a reason why all the surface grinders were located next to a cinderblock wall!


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## Andre (May 17, 2016)

gi_984 said:


> This is the way I was taught.  Seen more than one part launched off the table at the tech school.  There is a reason why all the surface grinders were located next to a cinderblock wall!


I threw a part once, it nearly threw 30 feet and took a small chunk out of the wheel. Thankfully everything was okay.


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## maker of things (May 18, 2016)

I think I'm going to try to NOT do that (throw parts that is).  I don't think I would enjoy it very much.


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## intjonmiller (May 18, 2016)

Throwing a part is nowhere near as bad as jamming a part between the spindle and table and damaging the machine itself.


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## Billh50 (May 18, 2016)

One place I worked at if you launched a part it went out a window into the wooded area next door. Didn't understand why the boss wanted the windows open til I launched a part. He would go outside to find the part and have a cigarette while he was out there.


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## intjonmiller (May 18, 2016)

intjonmiller said:


> If you have the budget for it, I recently saw that Suburban Tool at least used to make one that had alternating coarse and fine poles. I believe Tom Lipton showed it (used) in a video on his Oxtool YouTube channel. That strikes me as an ideal design.


Here you go: https://www.subtool.com/st/dmb_magnum-force_permanent_magnetic_surface_grinder_chucks.html

Just $1,117 for a 4"x4" Suburban Tool Magnum-Force chuck with both fine and standard poles.


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## gi_984 (May 19, 2016)

> Throwing a part is nowhere near as bad as jamming a part between the spindle and table and damaging the machine itself



Depends.  Launching a largish pointy piece of steel and killing someone is considered bad also.  A machine can easily be replaced or fixed.  Perspective is a *****.


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## intjonmiller (May 19, 2016)

Obviously


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## projectnut (May 26, 2016)

A "small part" usually defined as one that crosses less than 5 poles of the magnetic chuck.  If the part is less than 1/4" thick you may get away with it spanning only 3 poles.
To grind "small parts" on a wide pole chuck you can use "magnetic" parallels or magnetic V blocks.

https://www.google.com/?gws_rd=ssl#q=magnetic+chuck+blocks&tbm=shop

The blocks aren't actually magnetic, but are rather laminated blocks that allow magnetic fields to pass through them to hold the part.  The spacing of the laminations allows more fields to be generated, however they are somewhat weaker.


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