Flowering Elbow

Step 3 – Find New Magnets

This is probably going to be a tricky bit.  I went to elaborate lengths to acquire some neodymiums that were an exact dimensional match to the old ferrite ones.  However I have come to the conclusion that this may not have been strictly necessary.  You could, for example experiment with a number of bar shaped magnets of appropriate proportions, say having 5 or 6 of them replace a single ‘arc segment’ shaped magnet.

For reference here is the dimensions of the arc segment magnets necessary for the Bosch PSB24 VE-2

Remember you will need an opposing pair – so one that is polarised North – South along the arrow shown in the diagram and one that is the other way round (South – North).  This is important! If you have two magnets polarised the same way it will not work.

Other considerations

The material of the magnet is important.  We want rare earth magnets because they are super strong. Neodymium magnets, are a kind of rare earth magnet. Luckily the material used in rare earth magnets really isn’t that rare at all, and with new manufacturing techniques the price has come down quite a lot in recent years (though still not enough to be found on any but the highest quality motors).

So we want Sintered NdFeB (or neodymium) magnets… It will need to be able to withstand a bit of heat, which, neodymium traditionally is not that great at.  There are many types or grades of neodymium though. Being rated by a number (which is roughly equivalent to its strength) and a letter (which denotes its resistance to heat). The ones I opted for, for example, are:

N 40 SH

40 is an indicator of the flux density and SH means it withstands 150 degrees C before it starts to demagnetise. Standard N40 magnets start to demagnetise at just 80 degrees C. This is a link to a useful “table of grades” – sorry this website expired.

A Sintered NdFeB N40SH Arc Segment magnet, coated with Nickle then Copper then Nickel again (Ni-Cu-Ni). Lovely.

Leave a comment to let people know if you attempt this, and how you get on acquiring magnets.  If anyone is interested (in the UK) I have a few left over from the drills I have converted.