Tool geometry is generally better with inserted parting blades vs HSS ones.
The tool holder for the insert is skinnier than the insert itself - less chance of it binding in the kerf as the cut progresses deeper and things heat up and expand - closing the kerf and thus having a tendency to pinch the blade shank. Also, the insert is relieved backwards from the cutting edge. The red arrows are not parallel (yes, the insert has the front left corner chipped and is u/s).
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There is no kerf relief on an HSS blade - unless you grind one in it. Blades have a tendency to pinch unless you use a kerf widening strategy (as has been described above, I believe). The two arrows are parallel.
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For cutting fluid I have had good success with the water soluble stuff from PA. I use it straight on all drilling and cutting ops on all types of metals.
https://www.princessauto.com/en/cutting-oil-coolant/product/PA0008034012