Finish Good then Bad cl300

[Anonymous]

If I recall correctly my challenge to SoD was to do with a statement that HSS and insert tooling remove metal in different ways. They don't; in both cases they shear metal from the work. There is significant distortion of the metal as it is removed which takes energy and manifests itself heat, Hence the saying that most of the energy used in removing metal is carried away in the swarf as heat.

Of course there are differences of degree between HSS and inserts. The moulded inserts tend to have a slightly rounded edge so they tend to be less good at shallow depths of cut and/or fine feed rates. But that isn't absolute, it depends upon material.

Arguments about the horsepower used by HSS or inserts is the wrong metric. What is of interest is the power needed per unit volume of metal removed. Since inserts can run at much higher temperatures than HSS as has been said the shear zone can be red hot. Hence the metal is soft and more easily sheared. The insert may need to be running fast and a high DOC and feedrate to achieve this. So the absolute power may be higher, but the power per unit volume may well be lower.

While I don't do it often I have had swarf on the both the lathe and mill coming off dull red in subdued light with carbide tooling. You definitely do not want that going down your shirt front!

Andrew

[Author]

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