Even though the vast majority of copper EDM electrodes for injection mold making are machined by CNC machines, knowing how to grind copper is a valuable skill in the surface grinding process. There is always the odd job, or rework that requires manual grinding of copper.
One of the main reasons copper is avoided is because it is difficult to grind and it requires additional handwork after machining. This is due to the annoying burrs thrown up by machining, whether by milling or grinding.
Flood coolant is a great way to avoid the burrs, however, most manual surface grinding operations do not use flood coolant. Even a peripheral spray mist helps, but then you have the problem of a very messy operation.
The solution is as simple as your wax candle at home. All you need to do is load the aluminum oxide wheel with the paraffin and amazingly the grinding operation works!
Wax, paraffin, coolant, stoning oil or special wheel dressings all work
You can try any of the above wheel dressings and figure out which one works best for your particular application. The kerosene stoning oil is a good choice, but is quite messy and you will smell like a diesel mechanic at the end of the day.
What kind of grinding wheel?
By simply applying one of these wheel dressings, you should be able to grind many electrodes without having to redress the surface grinding wheel. Tips such as these are not found in most mold making training programs, they are the result of experience.
The coarser the grinding wheel, the better. For example: if you can use a 46 grit wheel instead of an 80 grit, do it! The extra spaces in the wheel structure will absorb the wax or kerosene and make your grinding easier.Use flood coolant, if possible. This is not always an option with manual surface grinders, but if you can, use it. Peripheral spray attachments also get the job done, with a big mess.
You can learn a great deal from your supplier as well, some companies offer sound advice as well as products to make the process easier.
Here is a link to the MSDS sheet on copper, in case you have any health concerns.