Coolant and rust

I seem to have an ample supply of used hydraulic oil. I've been using it for cutting fluid . I even use it mixed with acetone for rusty part clean up. I get it free so why not.
 
On the lathe I use a brush or spray bottle of cutting oil (Oatey?) from the plumbing department at Home Depot or Lowes. On the mill, I sometimes use flood coolant, KoolMist 77. I mix it just a tad richer than the instructions. I've only found rust under the vise and dividing head, after they'd been in one place for months. The rust just wipes off with a shop rag.
 
I used to use a coolant/cutting fluid sold by that mail order place that is now MSC (?). Enco was it??

I don't see it listed in the catalog anymore. It worked pretty well and did not produce rust if left unattended for a time....
 
Unless you need high production levels there is no need of coolant for most hobbyists. Control speeds, feeds and d.o.c. to keep chips and tools from getting too hot. Water based coolants are more trouble than they are worth when you only really need a lubricant. If cooling is actually necessary when cutting dry then consider air cooling first. If using cutting oil flooding will cool things some. ATF would be my first choice.
 
Tozguy

Doesn't a "coolant" also lubricate?? It sure makes cutting easier in many cases.
 
Yes the additives do lubricate a bit among other things but water does the cooling not the lubricating. If you only need a lubricant, oil is better than a water coolant with less of a hassle.
 
I can't answer you specific question about high humidity since we don't have that here. As far as coolants go, the most user and machine friendly coolant I have found for hobby use is KoolRite 2290. Non-irritating, almost no odor and no rust issues. I use this on my CNC mill. I change it once a year to get rid of the tramp oils. I've never had it go rancid. My tank has a few unsealed openings and I have a small aquarium pump on a timer that runs 15 minutes a day to keep it aerated.

If you do use coolant on the lathe it is always good practice to wipe and excess residue off the ways and re-oil after use. Having good way wipers helps keep the coolant out from between the sliding surfaces but it will find its way in so keep those well lubricated and use a way oil with rust inhibitors.

I have a coolant system on my lathe but have yet to have a job that would justify using it. If brushing cannot supply the needed amount for lubricant or I if want to use coolant I will use a spray bottle or applicator bottle.
 
I used to work in a shop that had a 15" Monarch lathe, which was a little piece of heaven, I might add. It had a built in coolant system and we just ran cutting oil in it. Never got rancid and kept everything oiled up nice, too.

It wasn't the ideal coolant for aluminum or anything like that, so we'd just leave the coolant pump shut off when working with non-ferrous materials.
I have worked in several machine shops that just
Run ridged cutting oil in everything but the grinders
It seamed to be the perfect cutting oil
You would get a lot of smoke but we didn't have a rust problem
 
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