John R, those are not regular holders, sorry.
To the OP,
Stick with HSS cutters. Your old Atlas is way too slow and not rigid enough for carbide cutters.
Most everything can be machined with high speed steel and they are easy to shape.
Ohio, Enco is a Taiwan manufacturer.
MSC is Manhattan Supply Company, possibly the largest machine shop supplier in the world.
Enco makes and sell junk, MSC sells every quality level from Junk to Swiss.