Another fly cutting question.

[higgite]

Bear in mind, an amateur is asking the question I’m about to ask. For you more experienced guys, the color of the chips looks a little dark to me, but I haven’t milled much steel. Could a too fast feed rate give chips of that color and be contributing to the rough finish shown in John’s pics?

Tom

 

[John TV]

Regarding the chip color, I mentioned that I was having trouble with hard spots, before the trouble I was using HSS bit and the chips were bright with no sign of blue. Hit the hard spots and dulled two bits, switched to carbide and many chips were blue.

Yesterday I took the cheap braised carbide cutter to a diamond sharpening pad and noticed a very tiny broken tip on the carbide, most likely from the interrupted nature of the cut. This may have contributed to the blue chips. I Polished off the chip, put a small radius on the part but didn't have time to test it with a cut.

I really enjoy getting the feedback. Thank you all.

John in MN


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[mikey]

Bear in mind, an amateur is asking the question I’m about to ask. For you more experienced guys, the color of the chips looks a little dark to me, but I haven’t milled much steel. Could a too fast feed rate give chips of that color and be contributing to the rough finish shown in John’s pics?

Tom

Hey Tom,
I'm going to be doing some guessing here so get ready, okay? As you already know, that beautiful blue color means that the heat from the cut is going out with the chip. In my experience, limited though it is, this happens when the cutting tool is generating a lot of cutting force. Either it is not sharp or the depth of cut is really heavy. Given that the chips are not that thick, I would suspect that the tool is not cutting efficiently. There, that's my guess, and a tool that is not cutting well will definitely affect the finish.