Below is my collection of rare earth magnets in their WELL PADDED packaging. Each arrow below points to packages of different sizes. They are stuck together in a proper polarization stacking scheme; Something that can be understood by reading the references previously provided above. Except in simple single stacks, it is not just a matter of matching North and South poles properly, but when bundling smaller magnets in rows a person should know / understand lateral polarity syncronization as well.
I always have a cheap magnetic compass handy and kept amply far away from the magnets when not in use. The compass is used to read the poles and direcions of flux lines around magnets including those in a guitar pickup; Especially in trying to figure out odd-ball pickup designs such as this one. A person MUST know the polarity of a pickup's magnet(s) in order to recharge them, or to properly syncronize the magnetic / physical placement of multiple pickups on a guitar if the pickups polarities are diffierent, or if a single pickup on a guitar has polarized metal co-located with the pickup such as pickups mounted on metal electronics plates; The metal plates themselves will become magnetized & polarized over time and will contribute to a pickup's magnetic strength if the pickup is oriented properly with the magnetized electronics plate. Supro "bunker" pickups are a good example: The magnets are mounted on a large ferrous metal electronics & bridge plate, and the top of the magnets are bridged by a metal plate. Over time the plates will get magnetized while the magnets lose some magnetism. A Player can disassemble a Supro "bunker" pickup for a number of reasons, as simple as doing a thorough clean-up of the guitar; And because it is commonly said that it doesn't matter which polarity faces up or down on those pickups, the Player can install the magnets in a polarity opposite from when they were removed. This puts old magnetically degraded magnets at odds with the polarity of the metal plates the magnets magnetized, resulting in the pickup being quite noticeably weaker than when the magnets were removed.
Packaged NeoDymium rare earth magnets:
Here is one of my extremely strong grade N45 Neo-Dymium magnets; It measures 2" x 1/2" x 1/2". 2 of these stuck together in direct contact have a clinging force of more than 500 lbs!
Here is forming a single stack of magnets, for use or storage. Since it can be extremely difficult to pull such rare earth magnets apart if they ever came in direct contact with other; A strong spacer must be placed between each one. Most factory spacers are made out of nylon or teflon in about the same thickness shown below; But cutting spacers from flat Tupperware also works, as long as it's thick enough to keep the magnets at-least 1/8" distance from each other. Thicker spacers will allow easier separation, and vice versa. Spacer material should be hard enough and tough enough to allow magnets to be moved / slid on the spacer; Such as the top or bottom magnet in the stack below could be twisted 90 degrees so that there is less magnetism at the point of stacking, ...which is a bit easier than sliding a magnet sideways on the spacer to pull it from a stack.
Example of recharging a Supro lap steel's magnets:
The diagram is an overhead view.
Actual picture is below the diagram.
For easy recognizition of the poles of magnets being worked with: Determine the existing polarity of each magnet and place a piece of masking tape on the North side and mark it well with an 'N'. Mounting the magnets in the vice can be in either N / S or S / N polarities as shown below. Once mounted in one polarity, that same polarity should be used in that vice because the rare magnets are strong enough and will magnetize / polarize the vice as well, so we would want future uses in sync with the vice's magnetism.
The combined strength of stacking magnets helps preserve their magnetism. The polarity above could be South on top and North on the bottom, as long as the polarity carries throughout the stack. Which way the sides face doesn't matter; Only the polarized top and bottom surfaces do.
Here is how rows of vertical stacked magnets are aranged for shipping space considerations. Again, it doesn't matter which way the magnets are rotated around their polarity axis:
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Another pageshows my portable carpenter's vice rigged for pickup magnets refreshing.
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( Or an entire guitar pickup with it's magnets facing in the proper direction to be in magnetic sync with the rare earth magnets ).
When mounting the magnets, open the jaws all the way or even remove the moving jaw; Then mount the rare earth magnets first and the guitar's magnets or pickup last, before continuing to close the vice jaws with care.
Here's how the attraction and repulsion would look had the top polarity of every stack not been arranged for their attractions and repulsions to coordinate a magnetic balance with each other. And remember that a whole stack and any given point in a stack has the same North / South orientation; So with rare earth magnets, mismatched stack can repel each other quite forcefully, yet amazingly balance out when their top and bottom polarities are coordinated.
HOWEVER; When magnets are stored in coordinated in rows of stacks, the domains along the sides of adjoining stacks can be such that their unlike poles to turn towards each others attraction, N to S; So stored over time some of the domains can become unaligned and the magnetism degraded to some considerable degree. So for storage the rows of stacks should be separated and rejoined as one or more long stacks so their domains will remain aligned. Keep the stacks away from each other by at least 6 inches or so. I box the stacks in corners of cardboard boxes to keep them separated with plenty of cushion. Matched poles facing up / down provide some nominal repulsion and keep the stacks from being attracted to each other:
Long stacks laying on their sides. Popcycle sticks are great for reinforcing the sides so they don't collapse from leaning or handling. Tape them down well.
Looking down on long stacks packed into the corner of a box.
Center the magnets face to face. That's easily done by hand when the vice is loose but magnets almost tightened face to face.
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for recharging / refreshing Rickenbacher horseshoe magnets.
NOTICE:The illustration below is ONLY to show the polarizations schemes of whatever mathod is used to refresh Ric horseshoe magnets. Using rare earth magnets to refresh horseshoe magnets would REQUIRE using spacers AND bindings such as high quality and strong ratchet ties, as shown in my vice pictures above, to bind the horseshoes and the rare earth magnets SECURELY, FIRMLY AND STRONGLY, because the magnets as illustrated here would be extremely attracted to each other and want to flip to attach to each other with great force. Stacking 2 magnets as shown below would require a strong box jig to stack them and their shims in and bind them together, because of the very strong force they would have to flip to attach themselves to each other. Example #2 is easier, recharging each end of one horseshoe one at a time; But example #4 actually works better for a number of reasons, if a person has the time to make a strong stacking & binding box jig to prevent the magnets from flipping while stacking and binding strongly. This should illustrate that it is much more preferable and practical to have horseshoe magnets recharged electrically by a professional; But using rare earth magnets instead is possible with some thought, planning, caution and care:
Keep in mind that if the 2 horseshoes do not have the same or similar amount of charge, ....such as charging them together in a pair such as example #5 would better provide, .....then one stronger than the other can create a difference in volume and a bit of difference in tone quality in the pickup; So it's important when charging one shoe at a time, that each one is charged in as identical a manner as possible, ....such as the same rigging, the same amount of time, with the same number and strength of taps with the small hammer. Having a gauss meter would of course make it much easier to get the "charges" balanced closely. If one horseshoe is nominally stronger than the other then you could use the stronger one on the smaller strings side of the pickup where less string mass could use the nominally stronger charge. See Rick Aiello's tech info on adjusting both adjustable and non-adjustable Rickenbacher pickups.
Horseshoes Rare earth magnet Spacers Spacers
A PERSON SHOULD BE ABSOLUTELY SURE THAT THEY CAREFULLY & THOROUGHLY LEARN PRECAUTIONS AND TECHNIQUES OF HANDLING RARE EARTH MAGNETS BEFORE THEY EVEN ATTEMPT TO TAKE SUCH MAGNETS OUT OF THEIR PACKAGE.
These rare earth (Neodymium-Iron-Boron) magnets are an extremely strong magnetic material; In fact it's the strongest permanent magnet that exists. They can interfere with Pace-Makers, Heart Monitors, and any other computerized device. These magnets can erase computer data or magneticly stored data such as hard drives, credit cards, audio tapes, that are nearby. They can erase the computer chip in a wrist watch being worn by someone working with these magnets. They can cause distortion to a CRT srreen such as TVs and monitors. Being cautious, I consider anything within 30" of these magnets as in their danger zone.
I USE PROTECTIVE GLOVES AND EYE GOGGLES WHEN WORKING WITH RARE EARTH MAGNETS, AND I STRONGLY SUGGEST ANYONE ELSE DOES TOO.
Rare Earth magnets are EXTREMELY STRONG. Two 2" X 1/2" X 1/2" N42 grade rare earth magnets like those used here have a combined contact pulling / holding force of more than 500 lbs. When handling two such magnets, ...if they come within a caution range of 2 feet from each other they will launch violently towards each other with astonishing force if not kept under positive control.
Working with two magnets, one in each hand, is not uncommon, and if a person gets them within about 2 feet of each other, one or both can violently leap out of one hand to rejoin each other, with plenty enough velocity and impact force to severly pinch and even break fingers.
Another potentially dangerous characteristic of rare earth magnets is that they are brittle, and if dropped should be deemed to likely shatter with a "zillion" pieces launching in all directions with great speed and force. If two strong rare earth magnets launch towards and impact with each other, their explosion can be twice the force of shattering one by itself. Picture smashing a marble on concrete with a heavy claw hammer and the pieces flying violently in all directions at high speed.
WORKING WITH RARE EARTH MAGNETS REQUIRES EXTREME CAUTION AND THOUGHTFULNESS OF METALLIC AND MAGNETIC SURROUNDINGS; Because those magnets are always interacting with ferrous metal and magnets and magnetic sensitive materials within about a 2 foot radius of the rare earth magnet. For instance, they will snatch up tools that can impact a person's hands with great force; Particularly nasty if the tool has even dull-sharp edges, such as screw drivers, punches, sheet metal, etc; And down-right dangerous if they suck up a razor blade, knife, scissors, sharp punch, nail, screw, etc. etc. etc.
It is IMPERATIVE that a person study and learn how to handle Rare Earth magnets before they try to handle any Rare Earth magnet larger than 1/4" on any side, diameter, thickness, etc. The 1/2"x1/2"x2" rare earth magnets shown on this page have an in-contact pulling force greater than 500lbs; A collision force about the same force as normally hitting a nail with a claw hammer, ....and that's the force that is likely to slam into fingers if one magnet jumps from one place to or towards a magnet in a person's hand; And they WILL jump towards each other with alarming speed and force if a person allows one, or anything ferrous, within about 10" of each other and not positively secured; I use 2 feet distance as my caution zone. Humans normally, regularly and subconciously move things within that range when handling things. I GUARANTEE that the majority of people handling rare earth magnets for the first several times will experience one magnet launching toward another or interacting similarly with another ferrous object.
Here is a great source for reading about magnetism. This is a good and very short mini review. It will help understand the basics and nuances of working with magnets. Pay particular attention to the section on magnetic 'domains' . Charging and recharging magnets is merely realigning domains into a magneticly polarized direction.
BEFORE a person takes rare earth magnets out of their packaging, they should have a clean and clear work area and assign a spot for each magnet on the work area that is no closer than 30" from any other magnet or ferrous object; And review the Safety precautions said here on this webpage before unpacking them. IF YOU HAVE A PACKAGE OF PROPERLY STACKED NEODYMIUM MAGNETS, THEN THE PACKAGE'S MAGNETIC STRENGTH IS MULTIPLIED BY THE NUMBER OF MAGNETS IN THE PACKAGE, WHICH CAN BE VERY VERY STRONG; And thus need extra distance from things they might damage or be attracted to.
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DISCLAIMER: The information provided on this website are for educational purposes only, and are not instructions. Anyone using information on this website should study and learn themselves how to do anything that presents a danger or potential for harm.
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ABOUT MAGNET POLES and
DETERMINING THEIR NORTH AND SOUTH POLES WITH A MAGNETIC COMPASS:
Confusing unless known and thought about. The illustration below this text will help:
In the air magnetism (flux) flows from magnetic north poles to magnetic south poles, and from magnetic south poles to magnetic north poles inside a magnet and the earth. A magnetic compass's north needle points to the earth's geographic north pole which is actually earth's magnetic south pole. Therefore the north end of a magnet on a float in a bowl of water will swing to the earth's geographic north pole (magnetic south pole) while the south pole of the magnet will point towards the earth's geographic south pole which is earth's magnetic north pole, which is how a compass works. HOWEVER, both the magnet's and the earth's internal flow of magnetism is a loop, into their magnetic south poles and on through their material to their north poles, exiting the north magnetic poles, swinging around in the air to follow a path in the air back to their south poles, in an infinite loop. A magnet on a float in a bowl will be aligned with the direction of flux flow back up to the earth's magnetic south pole located at it's geographic north pole. See my illustration below this text's next paragraph. This link goes to brief scientific info about the magnetic poles of earth and magnets:
Remembering that the earth's north pole is actually a south magnetic pole, makes understanding the 'like poles attract' / 'unlike poles repel' behavior of a magnetic compass easier, such as when using a compass to determine the polarity of magnets. ie. a magnetic compass needle's north polarity points in the direction of and aligned with and pointing toward the geographic north direction in the earth's flux field that is flowing toward the earth's magnetic south pole located at the earth's geographic north pole; Unlike poles attract each other. Likewise, the north compass needle will point towards the south pole of a magnet, along a magnet's flux field flowing through the air from the north to the south pole of the magnet ! The north / point of a compass is attracted to an unlike magnetic south pole, while the south pole of the compass needle tail is attracted to an unlike magnetic north pole. My illustration provided below shows what compass needles would look like at random locations in either the earth's magnetic flux field or in a magnet's flux field. Keep in mind that a magnet's flux field is about 100 times stronger than the earth's flux field, so a compass located far from a magnet would point toward the earth's geographical north, BUT the closer a magnet was brought to the compass, the more the compass needle would point relative to the magnet's flux field rather than the earth's.
Illustrated below is a 2 dimensional cross section slice of magnetic flux fields.
The jaws are NOT closed tight, but just lightly to the thickness of the ratchet ties. The wire ties keep the magnets from making contact, because once a guitar's pickup / magnet(s) are recharged then their being in direct contact with the rare earth magnet would cause allot of squirming and movement of the vice's several loose fittings while withdrawing the jaws when the guitar's magnets are recharged. We don't want that squirming / movement which would loosen / weaken the pickup's new magnet strength; We want the pickups to separate as straight and perpendicular as possible, ...which greatly helps to keep the guitar's magnets now-strong magnetism lined up tightly and thus strong. The tightness of alignment of the polarized molecules domains determines the strength of the pickup magnets magnetism.
It noticeably helps jar more of the domains into polarized alignment by tapping on the vice jaws with a small hammer such as a small tack hammer or small ball peen hammer 3 or 4 times for each of 3 or 4 times over the period of time allowed for the recharge / refreshing. There is no set time for a recharging / refreshing period of time because different alloys and quality of magnets being recharged / refreshed vary; "Trial and error" will be required until a person gets a good idea of how much a material needs to be recharged / refreshed; Testing a magnet to be recharged / refreshed before and after each session is a good indicator, by placing the magnet / pickup onto some ferrous metal such as the refrigerator door and feeling it's pull, or testing the pickup in it's guitar by comparing before and after recharging / refreshing. I generally allow an overnight period to get a good full recharge / refreshing as close to saturation as feasible, but actually an hour or so with a couple of times tapping the jaws with the hammer should be just fine for most guitar pickups. Most guitar pickups are originally charged to only about 25 gauss at either pole. Without a gauss meter, then comparing the magnetic pull of the pickup to be recharged with another known good pickup is a reasonable gauge of charge on the pickup to be recharged / refreshed; Such as comparing pull attraction to the refrigerator door. I have also compared magnets by seeing how a magnetic compass acts at different distances from each pickup or each magnet, measured with a yardstick and noticing at what distance one pickup starts losing the compass needle compared to the other.
Bottom; Mounting screws end
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Now let's get down to how I recharge guitar pickups & magnets
with rare earth magnets.
Magnetism (flux) flows from a magnet's or earth's magnetic north poles to each's magnetic south poles. Earth's magnetic south pole is located at earth's geographic north pole.
Shown are magnetic compass needles at random places in magnetic flux fields. The North end of the needle will point to the earth's geographic north pole because the north geographic pole is actually earth's magnetic south pole. So likewise a compass needle will point to the SOUTH pole of a magnet.
BUT, magnetism flows from south to north through the earth or magnet's internal material, then in the air flows from north magnetic poles back to the magnetic south poles, forming a 3 dimensional tube of infinite loops, shaped similar to an apple.
This is what a tube of infinite flux loops that make up the flux field might look similar to around a 6 string guitar pickup if the field wasn't invisible; But it would be much more "fuzzy" than shown here because the field continues outward getting weaker and weaker until it disappears. The strength of the magnets determine how dense and how big the flux field is.