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  • dian
    replied
    btw, some data on airgap and holding power:

    0.02 mm 90%
    0.10 mm 60%
    0.40 mm 22%

    (for pot magnets, no idea if that matters.)

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  • darryl
    replied
    I've watched a few of the videos where the guy receives a large wooden box and takes about 15 minutes of your time while he gets to the contents. Once finally there, a large neo magnet is revealed, which he then proceeds to stick paper clips to, etc. Ya ya, we know it's a magnet.

    Interesting to me is where they use wedges to slide two large magnets together to make one thicker one. The wedge invariably gets pinched right at the end, where some of it disappears forever between the magnets. Now what- you have one fatter magnet instead of two thinner ones. I want to see the jig that's used to separate them now.

    I have obtained a number of magnets for experimenting from Banggood. Prices were decent, delivery is free or cheap if you can wait 21 days, or 7 days if you pay extra for delivery charges. Locally to me, Lee Valley Tools sells a small selection of neo discs, up to 1 inch diameter, at reasonable prices. Places like hobby and craft stores seem to want too much for them.

    Interesting to me also is the iron nitride magnet development. Where car makers are moving away from neo magnets, largely because of cost and the dependence on China to source them, the iron nitride magnet would seem to be the cure for that- but nobody has been talking about it. I wonder why- but maybe it's because they have developed the induction motor to the point where it's not necessary to use permanent magnets anymore.

    I'm still looking at the idea of the stacked pancake, coreless motor. One pancake motor I have started life as an electric fan for vehicles. It has a printed armature with brushes riding on it, and is similar to some of the heater fan motors in vehicles. Some of those were pancake motors. I took mine apart and rebuilt it with neo disc magnets. I needed a special method of assembling it because the magnetic field strength was so strong I couldn't do it by hand. This motor now is probably best suited to a wind generator application, since it now produces a lot more voltage for a given rpm, and it doesn't have any cogging torque to overcome to make it spin. The air gap in such a motor is larger, so the design begs for the highest strength magnets in order to gain a decent power to weight ratio- perhaps we will see iron nitride magnets come into use for specialty applications.

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  • BCRider
    replied
    Originally posted by Bented View Post
    As a curiosity I bought a 1 1/2" Dia X 3/4" thick Neo disc magnet, it will cause pain and injury if mishandled, about $15.00
    I have no use for such a device, it is fun in bars however.
    We had cause to open up a bunch of old failed hard drives at work quite a few years back. We had the high power magnets all over the place and were giving them away to any and all that asked.

    We also showed off the usual parlor trick of moving one magnet around through our hands with another. One guy liked this so much that he insisted on getting two. I warned him what would happen and only did so reluctantly.

    It wasn't 20 minutes later that he came back with one of them and a new bleeding pinch cut on the thumb to forefinger web. "Here, take it. It seems I can't be trusted". He told me his co workers were no help at all when the magnets got an alligator like grip on the web due to laughing so hard. He finally had to just rip it away....

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  • nickel-city-fab
    replied
    Originally posted by Paul Alciatore View Post
    Where do I get the neo magnets? Much of my present supply was purchased from WalMart. But the last time I looked there, they had stopped carrying them.
    Google for "CMS Magnetics" they may be online as "magnets4sale.com". Very good to deal with, all kinds, shapes, and sizes. They are in Dallas, TX. Here's the link I use: https://www.cmsmagnetics.com/neo.php

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  • dian
    replied
    Originally posted by garyhlucas View Post
    That Currie point where the magnet no longer sticks is the exact temperature you want to anneal the weld on a bandsaw blade. Use a magnet as you anneal and when it stops attracting the mgnet you are perfect.
    i never welded a bansaw blade but the curie point is not the same for all steels. neither is the transformation temperature to austenite. while they indeed are in the same region (+/- 50°?), at least for medium carbon steels, you want to hold at (up to) an additional 100° over critical for a full anneal.
    Last edited by dian; 02-01-2021, 09:08 AM.

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  • Bented
    replied
    As a curiosity I bought a 1 1/2" Dia X 3/4" thick Neo disc magnet, it will cause pain and injury if mishandled, about $15.00
    I have no use for such a device, it is fun in bars however.

    Leave a comment:


  • Baz
    replied
    Magnetism and stainless steel.
    Every little iron atom is a magnet. In plain mild steel they are just randomly jumbled orientations and just like bigger magnets placed head to toe they can cancel out. When you apply a strong magnetic field they can get lined up and stay that way. When heated they get all excited like it's a day at the beach and jump around ending up all random again.
    Nickel is also magnetic, less so than iron but when you mix iron and nickel atoms at an atomic level the magnets align so as to cancel each other out and prefer that to getting aligned even by application of an external field. It depends on the proprtions though, Check your stainless cutlery and you will find it is magnetic.

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  • Paul Alciatore
    replied
    Glad you noticed the bevel trick. It was one of my better ideas and it, along with another of my other favorite ideas, solved the problem of mounting the magnets at a given distance below the surface. That known and relatively fixed distance helps to make that design successful in spite of not having a back-side path through a magnetic material. The CI or steel vise jaw provides a front-side path if the two magnets in a single magnetically held jaw are mounted with opposite magnetic poles facing out. So, even if it is not completely apparent in that drawing, I was following one of the principles that I spelled out; if only partially.

    I mentioned another of my favorite tricks. That was the use of a push-button nut on my drill press depth stop. The use of that nut both makes the adjustment of the depth stop fast and easy enough to ensure that I use it often, but it also allows a micrometer-like fine adjustment in the depth which will repeat from one part to the next. So while I was making a bunch of those magnetic vise jaws, I only had to set the depth stop once and then I could countersink all of them in rapid fashion. I love it when a plan comes together.

    I have used another method for getting the neo magnets mounted just a few thousandths below the surface of 1/8" thick, aluminum angle. I found that the magnets were just a few thousandths thinner than 1/8", so I just drilled a generous clearance hole in the aluminum and generously beveled both sides to provide a mechanical lock for the epoxy. I then placed the magnet and the back side of the aluminum angle on a steel surface covered with waxed paper. This put the back side of the magnet even with the back side of the aluminum. And the front side of the magnet was just a few thousandths below the aluminum's front surface. Then I used a generous amount of epoxy to fix the magnet in the hole with some pilled above the surface of the aluminum. When that cured, I removed it from the wax paper and added a sufficient amount of epoxy on the back side to the bevel there and form a small dome. This completely sealed the magnet in epoxy. Finally, I filed the front surface flat. I then had a magnet which was completely encased in epoxy, firmly attached just a few thousandths below that front surface. I have made several aluminum mounting brackets using this technique. No, there is no return path. But they do an excellent job of holding the parts they are screwed to against any steel or magnetic surface.



    Originally posted by Bob Engelhardt View Post

    Let your drawings be an example of what us others can aspire to!

    Your capture of the magnets by beveling the hole in the bracket is a great idea! I gotta' remember that.

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  • Stepside
    replied
    The magnetic "soft Jaws" are quite handy. BUT if you are holding a piece of steel in the jaws it will turn the swarf , the tap and the steel into a magnet. It cost me a brand new quality #6-32 tap last week. Used non-magnet soft jaws and the steel tapped perfectly.































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  • old mart
    replied
    Sorry about the number not working, I cannot post links at the moment and that number is on the ebay UK site.

    ebay UK 232560219553

    ebay USA 264659621292
    Last edited by old mart; 01-30-2021, 04:21 PM.

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  • Bob Engelhardt
    replied
    Originally posted by old mart View Post
    I bought a cheap magnetic swarf collector ...
    ebay 232560219553
    "No exact matches found"

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  • BCRider
    replied
    Paul, re your drawing. In looking at it again I realized that this would be alloy jaws. So no reason for the pockets to be flat bottomed because it would not change anything. A set of soft jaws made just as you show would be nigh on perfect. Sorry for leaping to the wrong initial thoughts.

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  • old mart
    replied
    I bought a cheap magnetic swarf collector which was less to buy than I could make one for. It is a non magnetic stainless closed end tube with a number of magnets inside it. They can be withdrawn and any magnetic swarf just falls off. There is a guard halfway along the tube to prevent the swarf following the magnets as they are withdrawn.
    ebay 232560219553
    Last edited by old mart; 01-30-2021, 01:34 PM.

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  • A.K. Boomer
    replied
    I remember having a "monster magnet" as a kid - was a big plastic horseshoe shaped magnet with the magnets mounted into the ends and would pick up quite a bit but nothing like today's neo's --- still was kinda magical as a youngster,

    times have changed and if you have small kids and think it would be cute to let them play with the little neo's you might want to think twice, although something to totally keep them amused with they also can be easily swallowed and then you better hope it was just one cuz if two or more then lots of times they will intersect in the small intestine and then connect two tubes together and not let go and cause the tissue to die off, huge problems and complications, that's if the kid survives...

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  • 4miller1
    replied
    Originally posted by I make chips View Post
    Just a free and easy tip:
    Save the magnets from old computer drives and stick them on the oil pans of your car engine and transmission. Then coat them in epoxy so they don't rust. You can't imagine the amount of steel they attract inside the pan of a transmission. They work even better on aluminum pans as the lines of flux are stronger than when passing through a steel pan.
    I just attach the magnet to the oil filter.
    Have not cut one open to check but figure they probably pickup some shavings floating by.
    jeff

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