I have a buffalo 6 inch dual wheel bench grinder cord and off on switch are missing how do i hook up the grinder is old and has 4 wires

SOURCE: older black & decker bench grinder

Usually a new wire wheel comes with different size bushing just for the problem you are describing. Either that or take it back and get one specifically for your tool.

SOURCE: switch and capacitor crapped out on 1/2 hp Sears bench grinder

Replacement should be simple. Just do a one for one hookup with the new part, after you unplug it first.
For a diagram go to;

http://www.searspartsdirect.com/partsdirect/getSubComp.pd?modelNumber=397.1949&productCategoryId=0721000&brandId=0247&modelName=CRAFTSMAN-1%2F2-H.P.-GRINDER&diagramPageId=00001&documentId=00023041&pop=flush

SOURCE: NEED ON/OFF SWITCH FOR BUFFALO BENCH GRINDER

You can get a replacement toggle switch at any hardware store look in the electrical department.

SOURCE: bench grinder, 110/220?? wired up properly

LIKELY the capacitor which is usually in the base is bad.

The capacitor shifts the phase angle in one of the two windings which creates a pseudo rotating field to start rotation.

SOURCE: need an on/off switch for a buffalo bench grinder

I had the same problem with a Northern Tools bench grinder. These are made in China and parts are hard to come by. I had enough room after removing the old broken on/off switch to install a single pole 15 amp light switch like you use in your home. I simply installed it horizontally and then put the switch cover on. It works perfectly. If you do not have enough room then look for any 15 amp or larger switch that will fit in the housing. Any on/off switch will work. You could even mount the switch on the bench in a switch housing and run the wires from the grinder to the switch and back if need be. Just be safe and make sure there are no exposed wires. As a last resort you could remove the switch connect the wires, eliminating the switch and use a plug in wall switch such as this.