I am making a 19 x 19 mm magnet which will be use to attach on an accelerometer for vibration analysis on a three phase induction motor. Instead of by using strong glue, I was thinking of using screw as mean of joining between the permanent magnet and the sensor.
Dear William,
drilling (or sawing) of neodymium magnets is absolutely not recommended. First of all, the material is brittle and fragile. Secondly, drilling causes combustible dust and, thirdly, the heat caused by the drill can possibly demagnetize the material.
Drilling can cause them to shatter and break. The drilling activity produces a powder of tiny particles of metal, which is flammable. The heat produced by the friction of the drilling can also ignite the powder, and burn or melt anything nearby. There are instances of subjects who tried to drill through a neodymium magnet, and found their drill bits melted.
Cutting or drilling a rare-earth magnet in half will not provide the subject with two magnets, but two pieces of metal that are no longer magnetic. The reason for magnetism in metal is the alignment of their magnetic dipoles or ‘fields’ in one direction. Heat provides energy to the dipoles of the metals so that they can break free of their original bonds and align in other, different directions. When machining or drilling a neodymium magnet, it is possible that the build-up of heat may cause it to demagnetize.
Specialists can work with the magnets with specialized diamond-tipped tools and constant water cooling. However, this normally occurs prior to magnetization of the material. You should also note that magnets which have lost part of their coating due to drilling will no longer be corrosion-resistant.
So, be careful!
Best,
A.
Yes, drilling a hole in NdFeB magnets is neither easy nor a good practice. We tried it many years ago using diamond-tipped drilling bit with liquid cooling. It worked, but as Angelo correctly pointed out, it is not a recommended practice. If time permits, I would rather recommend that you order a 19mmx19mm magnet with pre-defined hole. It is not a difficult process for magnet manufacturer to do this.
Indeed, drilling is not recommended, if it breaks during drilling pieces really fly away.
Dust can be poisonous. Magnets are Ni-Cu-Ni coated to avoid moisture and oxygen penetration. Normally glueing is a solution, but the magnets shrink and iron dilates.
So, most of magnets de-glue if they are used in both cold and hot temperatures.
Close to room temperature, gluing goes well, using cyanoacrylate or poly-urethane. A lot of glues such as epoxy do not bond well to Nickel.
A larger bond thickness is also a part of the solution.
If it is really important to have a perfect very wide temperature solution, contact me.
Alex
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