View Full Version : Questions on magnets
03-12-2005, 08:53 PM
Im looking to make an electrical switch of sorts, it will be a momentary type and i'm looking to use magnets instead of a spring...are there any magnets that are easily machinable at all....or would it work for me to magnatize some steel that i already have machined...and if thats not the route i should go....should i use some preformed magnets...do you think that epoxy would be efficeint
Thanks a looooaaad
03-12-2005, 11:05 PM
Sounds like you want to make or use a magnetic proximity switch (here's some info: http://proximity-sensors.globalspec.com/LearnMore/Sensors_Transducers_Detectors/Proximity_Presence_Sensing/Proximity_Presence_Sensors_Magnetic_Types ).
They're sometimes called reed switches. The "switch" part in encapsulated in a glass tube & is actuated by a magnet. The switch controls a relay that actually makes & breaks the power.
03-12-2005, 11:17 PM
Very few magnets are machinable, and the ones that are would generally be weak. There are so many sizes and shapes of pre-formed magnets that selecting one should be a piece of cake. Epoxy will work well to hold it especially if it fits in a recess. A reed switch is typically the answer for the device being actuated by the magnet, but a pair of contacts can be closed by having a metal piece being pulled on by the magnet to actuate the contacts. You would typically need a strong magnet to activate the contacts this way, so look at the range of neodymium magnets available today. They can be had in so many sizes and shapes, and some very small sizes as well.
An option is to use a reed switch to control a relay, which can then have as heavy of a contact as you desire. Reed switches by themselves don't handle much current.
I doubt you'd be happy with a magnetized steel piece, since it won't have as high a magnetization as a regular magnet, and even if hardened, it still won't hold the magnetism well.
[This message has been edited by darryl (edited 03-12-2005).]
03-13-2005, 10:44 AM
i'm not looking for a reed switch, but thanks anyways....
I looked at mcmaster and some of thier magnets...i saw some ceramic ones that would be very close but would just need some slight modification....and it says that they can be machined with diamond tooling....anyone ever have much luck with this?
Thanks a bunch guys
03-14-2005, 11:54 AM
I worked for a custom magnetics shop.
Any machining we did was with a Diamond Cutoff Saw (ceramic magnets), Diamond Grinding Wheel, Abrasive Cutoff Saw (Alnickel magnets), Ultrasonic Drills and/or EDM.
All machining of any magnetic material, was avoided like the Plague.
When designing Magnetic Assemblies, we tried to make use of Steel Pole Pieces, which (of course) are easily to machine.
Epoxy works good for Assemblies.
A good source for Shaped magnets is Edmund Scientific...
03-15-2005, 08:22 AM
Perfect! Thanks a bunch!