Mill Table Discoloration

[FuriousGeorge]

After I leave a vice or fixture on my mill for a long time (2 weeks), the table usually gets discolored. I usually scotch bright it with acetone and stone it down. This removes most discoloration, but not all.

What do other people do in this situation?

If you've never experienced this...what coolant are you using so I can get some

I know that one can expect a mill to have some battle scars, but I like it to look purdy.

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[Geof]

You are almost always going to get discoloration because it is electrolytic corrosion between two different metals. You can minimize it by having a film of grease between the two surfaces to exclude moisture and air, but even then sometimes over a long time you will get staining from the various compounds in the grease. In the past I have found the best material to use is simple vaseline because it does not contain any additives. Now I don't worry about it and I don't try to clean any staining off. If you try to clean down to pristine metal you will eventually take off enough material to affect the flatness of the table. Just skim the surface with steel wool or Scothbrite (green) but don't go too hard at it. You have to curb your desire for purdiness.

[MetalShavings]

The only staining or discoloration I've ever gotten was when I failed to leave a light coating of oil on the surface of my table. And most of that discoloration was underneath the vice. Now days after cleaning up I just spray a light coat of WD-40 over the table and that has solved the problem of discoloration and rusting.

The patina that my table now has is light and for the most part it's all the same shade so as far as how it looks, it looks like a normal solid metal color.

MetalShavings

[widget_maker]

You are almost always going to get discoloration because it is electrolytic corrosion between two different metals..

But both the vise and table are cast steel/cast iron so are not dissimilar.

[GLCarlson]

But both the vise and table are cast steel/cast iron so are not dissimilar.

Ah, not necessarily. An alloy may be primarily iron, but there will be minor differences in electronegativity because of alloying materials.

Here's an illustrative chart:
Galvanic Series
Note that there is a range indicated for most systems (aluminum alloys are particularly notable).

The essential point is that there will be galvanic activity, unless one happens to have a vise and table made from the exact same melt of cast iron. And even then, I wouldn't bet the farm. Those minor differences may only amount to a difference of a few millvolts, but that'll do it.

[bevinp]

Furiousgeorge,
Rust, staining and the effectiveness or otherwise of WD40 is frequent topic in this forum. A more recent thread is this one, which provides various experiences. It does seem to be related to the metals of the vise and table, and the oil/compound between the two mating surfaces.
Also some coolants will rust the open surface of metal if left overnight, others don't, regardless of whether the coolant is water based or not.

http://www.cnczone.com/forums/tormac..._finish-2.html
Bevin

[Steve Seebold]

What are you using for coolant? I have been using Swiss Lube Blazocut 2000 Universal in my machine for 2 1/2 years and there is NO staining on the table, and I run my machine 8 to 12 hours a day, and I don't blow the table off at night.

I let the chips sit where they are over night and vacuum them up in the morning after the coolant has had a chance to drain out over night.

[Beezle]

My table still looks great. I use Boeshield T9 on all surfaces, including the bottom of vises, etc. For coolant, I am using the stuff that Tormach sells. I've never had any corrosion show up, so I'm happy enough with that.

I've been using T9 on iron surfaces for years and have tried many other things and it seems to work best to me. On some tool surfaces I also use micro crystalline wax.

[FuriousGeorge]

I've been using the Tormach coolant as well as A9 for some operations. I'm not getting any rust, just some discoloration. The A9 seems to corrode the table more, so I always wipe that off after use. At the end of the day I usually just blow the chips of the table and clean it in the morning like Steve said. Maybe I'll try the Swiss Lube next time I need coolant.

[Beezle]

What are you using for coolant? I have been using Swiss Lube Blazocut 2000 Universal in my machine for 2 1/2 years and there is NO staining on the table, and I run my machine 8 to 12 hours a day, and I don't blow the table off at night.

I let the chips sit where they are over night and vacuum them up in the morning after the coolant has had a chance to drain out over night.

Where do you buy that?

[BTP]

I don't own a Tormach, but I've found something that works very well. Much better then WD40. It's called Fluid Film Fluid Film® | Corrosion Preventative, Lubricant and Rust Inhibitor It leaves a waxy film and ever since I've been using it between my vise and table I've not had any discoloring/corroding.