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MMurphy
04-16-2005, 11:02 PM
I'm just finishing up on building a grinding wheel balancer using magnets instead of knife edges or bearings.

I use 1/2 drill rod for the arbor (slide on plastic tapers to fit the wheel), I center drill the drill rod and solder a ball bearing in each end.

The ball bearing on one end rides, just touches, the magnet on one end. The other is in the air supported by the magnets attraction. The balance is very sensitive.

Here's my question. With the NIB (NEO) magnets available fairly cheap and powerful, I would like to build some magnetic clamps for my mill. And, maybe, build up another magnetic chuck for my HF surface grinder. I can't find (searching the net) anything that shows how magnetic chucks work, how to use AL or other materials to redirect the lines of force, and so on. In other words something practical, for building tooling, not toys.

Help!!

Don't want to use electromagnets.


[This message has been edited by MMurphy (edited 04-16-2005).]

[This message has been edited by MMurphy (edited 04-16-2005).]

Evan
04-17-2005, 12:21 AM
I don't think that is a good idea. Super magnets strong enough to hold something securely in place for milling do exist. They are freekin dangerous too. They can snag stuff from quite a distance. They can easily shatter if they strike somthing hard and spray little sharp chips of magnet that then will stick to everything in sight. They will magnetize whatever steel they touch and then you have a real chip removal problem.

Not a good plan.

WJHartson
04-17-2005, 12:28 AM
I agree with Evan on this. Beside being dangerous you will never get the chips cleaned up.

Joe

torker
04-17-2005, 01:29 AM
I have to second (or third) that. Wasn't thinking when I put a halogen worklight on my mill. Used a strong speaker magnet(epoxied to the bottom) to hold it where I wanted it. After milling a little project the base of the light looked like a big porcupine! And it was hard to clean.

Ian B
04-17-2005, 04:59 AM
Ok, maybe the idea of using neodymium magnets out in the open as milling clamps / swarf attractors isn't too good, but how about the second idea - make a magnetic chuck?

These are usually totally enclosed, and are actuated (I think) by a lever sliding a plate full of magnets in and out of line with ferrous blocks which form the external clamping surface. This would seem like an excellent use of the strong magnets.

Maybe also a magnetic base for dial gauges etc, with an on/off button?

Or a magnet on a rod inside a plastic tube for collecting swarf - collect the swarf, hold it over the bin and retract the magnet. They're available commercially, but look easy to make.

Ian

MMurphy
04-17-2005, 09:29 AM
Evan... Thank you for your advice and concern.

Let me expand a little. The magnets that I'am using currently (200-600 pound pull) can be very dangerous if handled without due care. I use AL keepers and fixtures to handle them. Like anything in a machine shop, I try to think thru what I'am doing with regard to safety, before I perform the action.

There are several lines of magnetic chucks and hold downs that are sold for use on milling machines. They are electromagnetic, so swarf is not an issue. Some can be field reversed, which tends to eliminate issues with parts becoming magnetic. I also have a fixture that I built that allows me to de-magnetize parts.

Two points: I have a lifelong facination with magnets. I love to experiment with them. I also love machine work (hobbiest). So, I'am exploring combining the two interests.

I took apart a HF magnetic indicator holder, and I can see how the combination of AL and steel is used so you can switch the magnet on and off. My surface grinder chuck is a cheapo, but I don't want to take it apart and possibly screw it up.

A website, books, whatever...to learn how to use magnets in a practical way, in a machine shop. The knowledge is out there, its already being done, I want to get that info into my tiny brain.,

WJHartson & Torker... Thanks for your response.

Ian B...Thanks for the suggestions. I have put the swarf collector on my project list. I wish we could collect AL chips in the same way.

I can't afford any of the available electromagnetic machine tool gizmos. They a generally intended for CNC use, under automated control. Very high prices.

My design criteria:

1. Can be turned on-off. No swarf problem. Like a surface grinder chuck.

2. Probally can't keep the parts from becoming magnetic. Have to use external de-magnetizer. Will try anyway.

3. Sufficient holding/clamping power for the intended use. Cutting tool forces.

4. Safe in the final assembly. no exploding, jumping thru the air, finger pinching and so on... The last will require me not to put my fingers or other body parts between the magnet and the held part when the magnet is turned on.

5. A great lot of fun.

Concern for safety is one the great things about this forum. Thanks again folks.

Mike

Point of interest. The CNC electromagnetics are designed so that the lines of magnetic force do not appear at the parts surface (like a surface grinder chuck)so chips do not collect and interfere with the cutting tool. Also, one of the designs actually allows the chips to be collected and automatically disposed of when the magnet is turned off. Pretty cool.

[This message has been edited by MMurphy (edited 04-17-2005).]

Evan
04-17-2005, 12:23 PM
200 to 600 lb pull?? Yikes!!! I don't want to be anywhere near magnets like that. Crap, I pinched out blood the other day with itty bitty 8 lb pull super magnets.

Working with that sort of magnet is like building fireworks. They sometimes go off when you really don't expect it. It's like working with high voltage too. Not for me.

John Stevenson
04-17-2005, 12:58 PM
A lad at one of my customers was playing with a couple out of linear motors.
They whacked together with his thumb in between them and it broke it.
He's only just started back to work.

John S.

tattoomike68
04-17-2005, 03:35 PM
I agree with evan, neomags are wicked take two and let them grab eachother and they grab so hard they explode and bust.

you think blood blister.

Paul Alciatore
04-17-2005, 03:38 PM
Masking tape is great for cleaning chips off magnets and magnetized tools. May require several applications with fresh tape each time.

Paul A.

MMurphy
04-17-2005, 03:48 PM
Hi folks


Paul A.... Great Idea, I've been using leather gloves and a paint brush!


Another point of interest...The people that I get my magnets from make NIB magnets up to 800 pound pull on special order (very, very expensive 6k before shipping). Somebody may make larger ones, but I haven't seen any info in the public domain (Web).

Any magnet over, say 50 pound pull, would be dangerous to handle with your "neked" hands. When I "graduated" hehe, to magnets over 20 pounds, I consulted with the folks I bought them from and they provided fairly decent descriptions of the keepers and fixtures that they use for handling during manufacture of the magnets. Made some and I always use them.

They told me that they rarely lose more than twenty or thirty people a day at their factory. With a total of 24 full time employees, all they have left between them is three fingers and part of a thumb.

Seriously, mags up to 140 pounds (2 inch square, 1 inch thick) are readily available from ebay and at least four web sites. And can you believe that they actually ship them legally in the US mail. What a hoot, imagine a postman stuck to a metal light post.

I suspect that, sooner or later, injuries especially to kids will end non-supervised sale of the NIBS. I would also expect to see labeling requirements indicating the hazards of dismantling or otherwise fooling with things like linear motors that contain NIBS.

In the meantime, hopefully, someone will point me toward info on magnetic chucks and such stuff while I still have enough fingers to try to build one.

Thanks

Mike "finger challenged" Murphy

By the way, I used two 20's on each side of my grinding wheel balancer. More than I needed it turns out. I have 1 600 and 1 200 pound pull NIB (special order cancellation 25% to me) for experiments. My project mags will most likely be 20-60 pound range.




[This message has been edited by MMurphy (edited 04-17-2005).]

wierdscience
04-17-2005, 09:19 PM
Why not wind your own electromagnets?It's not rocket science and for that there are several books around.

Most are just concentric coils lain up in a cast iron body and bedded in epoxy.

DBW
04-18-2005, 10:16 AM
<font face="Verdana, Arial" size="2">Originally posted by wierdscience:
Why not wind your own electromagnets?It's not rocket science and for that there are several books around.

Most are just concentric coils lain up in a cast iron body and bedded in epoxy.

</font>

DBW
04-18-2005, 10:28 AM
<font face="Verdana, Arial" size="2">Originally posted by DBW:
</font>

Sorry about the last post, I pushed te submit button before posting. What I wanted to say was that I designed a 5" x 11" electro magnetic chuck for a samll surface grinder. It requied
over 4000 feet of #26 gage wire with 140 volts
d.c. The problem was the wire alone would cost
over $80.00. Sooo I decided to buy a small Enco
permanent mag. one.

Ian B
04-18-2005, 12:11 PM
This guy seems to be selling some of the larger size magnets - not quite sure what you'd do with one - if it was in your pocket and you walked past your lathe, I'd guess about 60mph...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=1267&item=7504085602

Ian

MMurphy
04-18-2005, 09:41 PM
wierdscience & DBW...Thanks for your post.

I did a little checking on the web and there is a lot of info on doing electromagnetics.

Maybe I need to change my mind a little. Hate it when I have to sacrifice cherished notions.

Ian...Went to the link you posted. Based on the little data he provided, I would guess, maybe 1000 to 1200 pound pull. Wow!! Double wow!! You could use those to pull nails out of green wood. Thru your body if careless.

Showed the Ebay page to SWMBO. Definite negative response, no nore money for large magnets. She complains that all I ever do with the two large ones I already have is to go out in the garage where they are stored and poke them with a stick from time to time. Not fair. Not sensitive to a man's needs.

Big NIBs must be handled with special fixtures to avoid injury. The ones he is selling could kill. They could pull a bit of metal into if not thru flesh. I'm going to call this guy and find out how he ships those. The only way I can think of would be to incase the mag in a close fitting container of ductile or cast iron at least 1/4 to 1/2 inch thickness to short the lines of force into the iron. Thanks Ian a bit scary.

Mike "Afraid of those big NIBs" Murphy