Magnetic switch on new Cabinet saw

[Chris Mann]

Finally squirreled away enough money for a true table saw to replace my bosch bench top. Picked up the bridgewood 10lts from wilke machinery last week and have just now gotten the time to set it up.

Today I wired it all up and noticed that the switch hums when the saw is powered off. Is this normal? I might not have even noticed, it's just that it took me a few minutes to figure out exactly how hard I had to press the switch to turn it on in the first place, so I spent a bit of time checking over everything and that's when I noticed the hum.

thanks
-chris

[Ken Garlock]

First, welcome to the creek, Chris. Wade the creek often and enjoy yourself. :)

I am told by the Wilke people that yes it is normal for the magnetic switch to have an low level AC hum. I don't know the source of the hum, and I see no reason for its presence. You will notice that the plastic cover on the switch will over time get just a little bit warm, not hot, but just a little warm. If you listen when plugging in the saw, you will also hear a little click. I have noticed the same click when I plug in my Mini Max band saw.

I haven't worried about the hum, but I don't leave the saw plugged in when I am not in the shop.

[Ted Shrader]

Hi Chris -

Congratulations on the new saw! You know you will be busted by the picture police (Tyler & Chris P) :)

The relay used to hold in the line contacts when the saw is switched on is the source of the hum. Should not be a problem. I have two machines that don't hum, one that does. It is a wise idea to leave your machines unplugged or switched off at the breaker panel when you quit for the day. Just an added safety factor.

Regards,
Ted

[Ken Fitzgerald]

Welcome to the 'Creek Chris! Congrats on the new saw........Tyler and Chris will be at your door screaming about this being an unofficial gloat. :rolleyes: :D

[Bill Turpin]

Magnetic contactor hum is caused by several things. Relay coils, solenoid valves, and motors all pull locked rotor amps. After the armature of the relays and valves go to energized position and motors get up to speed they pull running amps. LRAmps are six times the running amps. If the magnetic fields are not completed the extra amp draw causes heat which eventually burns up the device. Contactors that hum can have less than perfect (el cheapo) engineering. Slightly off in the number of windings in the coil, chipped laminations in the magnet assembly, etc. The biggest cause of hum is rust, dirt, or SAWDUST on the faces of the magnet assembly. There are two steel laminated magnets that are shaped like capitalized E's. One points up and one points down. One is stationary and has the coil around it's middle. Crud on the faces(only a few thousandths of inch) prevents the moveable magnet from completing the magnetic field. These polished faces, which MUST NOT be lubricated, often rust before new machines are sold. They can be cleaned with very fine sandpaper, and blown out with air. Transformers, which may be found in some control boxes, also hum from similar reasons. The AC sixty cycles also comes into this. Be sure all fastening devices are tight. CAUTION: Play inside the control box with the device TOTALLY UNPLUGGED.

Bill Turpin in WNC mountains