[jaru-eri]

For smaller engravings on copper and silver, will it be ok to use a cooling spray on the carbide bit instead of cutting oil under the process? Are there anybody here who have tried that?

[xalky]

I like using cutting must on the milling machine and the lathe. Makes way less mess and just as effective.

[joeavaerage]

Hi,
with soft materials like silver and copper you may not need any cooling or even lubrication but clearing the chips away from the cutzone.

Recutting chips is a sure-fire way to get built-up-edge. Just blowing the chips away with a continuous air blast may be all you require.

Craig

[ATScuba]

Personally, when cutting copper and silver - we use straight oil - it doesn't take much flowrate, and it doesn't create as much smoke/mist in the work area unless you are running high spindle RPMs (>20k) - You can cut it with water base mist - but sometimes it will smear and leave marks. The oil keeps the soft materials from welding back together when cutting.
BTW - we use Hangsterfers HardCut NG - but you could probably use any decent grade mineral oil

[bogone]

The only thing you have to watch out for on copper is staining. A lot of oil based water soluble coolants will stain the copper as will some oils.

[joeavaerage]

Hi,

The only thing you have to watch out for on copper is staining. A lot of oil based water soluble coolants will stain the copper as will some oils.

Funny, but thats not what I've found, perhaps I just lucked out on the choice of water soluable oil.

Some time ago I was making circuit boards but that had VERY thick copper layers, 420um thick, whereas normal 1 oz board has a 35um
layer. In order to do this I used 0.5mm endmills as regular V-bits lead to an unacceptable trace thinning. To get any sort of useful life
from such small diameter tools in a proportionately (420/500=84%) thick material I used flood coolant.

Naturally I added some water soluable oil, and I got some locally, Total Lactuca LT3000, and it worked fine without any staining.

As it turns out I'm now of the opinion that the oil is actually a small part in the sucess and I now attribute the success I had to the
removal of chips from the cutzone. While I used flood cooling by directing a moderately powerful stream into the cutzone I have susequently
found that a continuous air blast into the cutzone works nearly as well.

With soft and 'gummy' materials like copper and silver and certain near pure aluminums if a chip is re-cut its propensity to 'weld' itself
to other chips, the tool or the base material is huge. If you eliminate the re-cutting of chips you can go form a 5% sucess to 95% just
like that. That was certainly my experience with cutting the thick copper boards I was making.

Craig