For tapping and threading stainless, the best product we have found is called "Moly Dee" by Castrol. It's not cheap but a little goes a long way. For general machining (drilling, milling and turning) we use a full synthetic coolant.

John

~ J Lucas
2006 GMC Envoy 4.2 I6
2023 Ram 2500/Cumins 6.7 I6
2010 Jeep Grand Cherokee (Wife’s)
2002 Silverado 2500 Gas 6.0
1941 Chevy 1/2-Ton
1942 Chevy 1.5-Ton SWB
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