Used motor oil as cutting fluid

Or try something really novel -- a fluid that's made for the job. A gallon of Trim Sol or similar water-miscible oil will cost around $20 - $25, and it will last you a very long time. For most machines that have a sump, you mix it somewhere around 10:1 with water.

If you use a good grade of cutting fluid (Trim Sol is well-tested in industry), you'll save enough on cutting tools to pay for it in no time. I had a quart of Trim Sol and it lasted me three or four years. And I did a heck of a lot more machining in those days. I mixed it 5:1 for use on my South Bend.

-- Ed Huntress

Is that the kind of fluid that looks like fat free milk?

After it's mixed with water, yes, it's milky. That's your basic "water soluble" (actually, miscible), oil-based coolant, which has been around for more than 50 years. Some of the newer synthetics don't get milky -- and they really are water soluble, rather than miscible.

For the small shop, the basic miscible coolants are all you'll need. The fancier stuff can pay off at high speeds with multi-coated tools, but we're not likely to see their benefits in non-production applications.

Again, though, all of these water-diluted fluids should be thought of as coolants, not as cutting lubricants. Miscible oils are not as good at lubricating as the lard-oil and mineral-oil-based cutting oils. But they're close. Mixed 5:1, they're lousy coolants but better lubricants. That 5:1 mixture for my South Bend was recommended to me by the engineers at Master Chemical, who make Trim Sol. If you apply your cutting lubricant with a brush or with a drip, you're really after lubrication rather than cooling. If you need cooling, you need a mist or a jet. That's when you use the regular dilutions.

-- Ed Huntress

=========== What a novel idea!!!!

For home/hobby shop use, where the standard black sulphur oil is too thick and you want/need some cooling effect, try diluting the black sulphur oil with mineral spirits paint thinner [varsol]. The varsol will evaporate quickly cooling the tool, the sulphur will help avoid chip welding/edge build up and the oil will provide enough lubrication.

How many people have and use a coolant pump/sump setup? Some how this seems like overkill for the home/hobby shop.

also see

I do. I started with a 1-gallon Little Giant flood-cooling pump, for the drill press. What a difference that made.

I considered the Little Giant for the Millrite vertical mill, but the table doesn't have a drain fitting, and I figured that flood would be far too messy.

I started with a cheap mister with one control, but it filled the shop with drifting clouds of mist. I changed to a two-control mister (Noga), which works much better. I move this mister between mill and Clausing lathe at present. It is slightly messy, but does work. One fine day I'll get a second mister.

Joe Gwinn