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Milling slots in annealed stainless steel Near Dry

Supplier: Unist Australia By: John Barker
02 February, 2010

We threw down the gauntlet to a large machine shop in Bendigo, Victoria in Australia, that manufactures parts for the Australian defence forces.

We said there are no limits to Near Dry Machining, and that we can eliminate flood coolant. The customer offered to run a controlled trial on a vertical mill to prove the point.

Material:  AMS-5643 (17-4PH) Annealed stainless steel
Cutter:    18mm  two fluted slot mill (High Speed Steel)
Depth of cut:   8mm x 3 cuts. (24mm total depth)
Length of cut:  500mm
Feed rate:  90mm/min
Spindle speed:  405 rpm

The first test was run using traditional flood coolant. Three passes were taken after which we examined the cutter and the slot. The cutter showed signs of wear on both the side and bottom face therefore the cutter would most probably not have done another cut successfully. The customer stated he was happy with this result which they had predicted. Now it was Unist's turn.

We fitted up a Unist S102607A Coolubricator a special unit designed by Wally Boelkins the founder of Unist Inc Grand Rapids USA. The unit is a standard Coolubricator fitted with an automated air blast pulse "Chip Blower" we knew it was crucial to evacuate the chips from the 24mm deep slot we were cutting in order to achieve a positive result. We used Coolube 2210EP.

First cut, beautiful. Chip colour, nil to extremely pale straw. No heat in the Job, no heat in the machine and no heat in the material.

Second cut, as above.

Third cut, as above.

The surface finish on all three cuts was absolutely first class, especially the walls. They were so smooth, and there was no comparison between the Unist finish and the flood finish which looked torn. As expected the cutter did have wear, in fact it was agreed that the wear was just about identical to the cutter that was used with the flood coolant.

The outcome was a success; we proved that we could machine difficult material "Near Dry" and eliminate flood coolant. The customer was very impressed.

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