Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Stefan, to forgot to explain the "heat" issue.

Carbide, with and without various coatings is used extensively in
metal machining. Carbide can take a tremendous amount of abuse and
keep on cutting just fine. As an example, when milling with a
carbide indexable insert endmill (or face mill etc.), the chips come
off the part Blue-Hot, hot enough to cause an instant burn on the
skin that will blister. These cutters can have anywhere from 2
teeth to dozens or even more teeth. More often than not, people
will use coolant (a water with synthetic lubricants) on these
cutters when cutting all sorts of hard and soft steels. In those
cases, that insert is getting very hot while in the cut, then as the
tip exits the cut with each rotation it is blasted with cold water.
The inserts survive that very nicely. What most machinists don't
realize is that you can cut just as effectively and get longer tool
life without using coolant on these types of cutters.

However, as I have done during demonstrations with big machines, you
have to watch where all those chips pile up. On one particular
machine I was deonstrating to Snap-On tools, we were cutting a large
die base of tool steel. We were hogging LARGE amounts of material
off the die base without coolant and everything was going along fine
till things got blury. What happened was the chips piled up against
a plexiglass door, built up enough heat to ignite the plexiglass.
Even with the small fire, the customer was still happy as a pig in
mud to buy the machine :-)

Chris