I need to add a slot to the table plate of my Harbor Freight (Central Machinery) ½ ton arbor press.

It's obviously cast iron, but the surface is polished, so I'm not sure of its exact composition or if the surface is tough and it has a softer interior.

I don't have any carbide end mills, but I have some surplus HSS mills I don't mind destroying in this process.

Any ideas or suggestions?


2 Answers 2


My experience with cast iron in the process of milling and lathe turning (minimal, but valid reference) is that cast iron will cut nicely with ordinary HSS tools. The swarf will be granular, not long streams of ribbon and the surface will be moderately smooth, depending on your feed and speed.

A few references on the 'net suggest that it is "self-cooling" due to graphite in the iron. Another few references also suggest that use of coolant will create abrasive mud which will dull the tools.

You won't be destroying your tools.

  • In grey iron the graphite flakes are "chip breakers" preventing long swarf. Jul 7, 2019 at 22:04

If it is grey cast iron ( most probable) it will cut like tough wood- no special tools at all. If nodular of malleable cast irons it will be slightly more difficult to machine ( more ductile , similar to ordinary carbon steel) but no special tools. It should not be white iron as that is brittle.

  • 1
    ASM recommends 35 to 175 surface feet/minute for milling depending on grade , with feed of 0.008 to 0.016 in./turn ( hss tools). They suggest no cutting fluid as the small chips from cast iron cake-up and are difficult to remove from work and tools. Jul 8, 2019 at 0:42

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