during the machining process What color would you prefer the chips to be ? and What does this color of chips signify?

Depends on many things, Material cutting, inserts, coolant, type of cut. Whats the specific application?

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Chips should ideally have the same color as that of the original material. Any change in color indicates overheating of part during machining and you need to check your cutting speed, feed and coolant flow, to rectify this problem.

Amit
www.emachineshop.com

I am going to disagree with you as what you've written applies to some situtaions, but certainly not all. I've done a LOT of machining in my 30+ years in the business, and can tell you that with many types of metals being machined, blue chips can be a very GOOD thing. Today's cutting inserts (especially cermet, ceramics, and CBN) are capable of running at very high temperature at the cutting edge without excessive wear, and chips that have changed from the original color of the raw material when cutting without coolants or cutting oils only indicate that the chips are carrying away the heat from the workpiece and the cutting tool. This is a GOOD THING!

I've seen VERY hot chips come off of hardened mold steels (54Rc & up), being machined DRY with top-nothc latest-technology solid carbide milling cutters. The newest coatings and carbide compositions are nothing short of wonderous.

That said, chips turning color are generally a bad sign if using old-school high speed steel cutting tools (such as standard drills), and heat like that will lead to the tool's early demise.

completely agree with ken