Cutting oil vs Old motor oil and non-detergent oil

My go to product is TapMagic, I use it for all cutting operations, dispensed from a tuna can with a 1" brush, I buy it by the gallon. It dramatically enhances machinability and does not stink up the shop, as with sulfurized oils; old motor oil is a non starter.
 
This is very old knowledge.... Long before I was doing machinist work, when I acquired a UniMat DB-200, I hung around the ship's machine shop. Next door to the electric shop. This in the late '60s... We had a (I think) LeBlond engine lathe of some 16 inch swing, maybe 3 feet centers.

In any case, a serious shop. The machinist, ex-navy chief, ex-air force, ex-bunch of stuff, was a darn fine machinist that used "9250" for everything but cast iron and aluminium. 9250 was a very high detergent diesel engine oil that was almost universally used. Even swiped to do personal automobile oil changes. Conceded, if the auto engine had weak spots, the 9250 would make it leak like a seive. A strong detergent...

As cutting oil, it smelled but what on a ship didn't smell bad. He used fat leavings from the galley for cast iron. Not sure what he used for aluminium, it seldom came up. The 9250 was used new, and well wiped down after the job was finished. All manual lubrication, no automatic oilers. The ship dated from the '40's and there was no sign of corrosion, anywhere. Including the ten diesel engines that had fuel oil(diesel) purifiers but nothing for the lube oil. As they leaked down, they were topped off. Some 30 gallons full. I'm sure there was some salt water contamination but very low. Oil cans were filled in the engine room, two decks down, from the engine lube oil line and accounted for as engine lubricant.

Since I have become an apprentice grade machinist, I have used what I find to be a near equivilent for 9250 for my stuff.(diesel engine rated oil) Everywhere except the models, where the plastic gears take exception to petroleum lubricants of any sort.

Don't know if this will help, but it did provide me the (rare) opportunity to tell sea stories. For people that know ships, she was 270 feet stem to stern, 65 foot beam(a pig), and 30 foot draft.
 
Many years ago when I got my first lathe, I was playing around and was turning some steel scraps. I didn't have cutting oil yet, so I tried some 10w-30 motor oil. To me, it seemed like the motor oil formed a film that was very difficult to penetrate, and required more tool pressure to make it cut. If you think about it, that's what you would want a motor oil to do in an engine. Cutting oil doesn't have that same film tension, and allows more free cutting and less tool pressure. Just my observation.

I just buy the cheap Oatey brand cutting oil (I prefer the clear formula) at Home Depot or Menards. It's cheap and lasts quite awhile. For aluminum I use WD-40. I buy it by the gallon anyway, so it's always around when I need it.

GG
 
Cast Iron always machine dry. Heaps of free graphite and any moisture/fat/oil leads to disaster. No exceptions to this rule and it's been that way since the 1700's.
 
There is another thread very closely related to this under 'Coolant vs Rust'.
I'm finding this subject fasinating as there is overlap with what I know and with the knowlodge of people on the opposite side of the globe but definately regional differences.
On the other thread mention has been made of useing old hydrualic oil, cutting cutting oil with Kerosene ect. As a confirmered broke person, accomplished scrounger and all-round miser when it comes to consumerables I'm sure that the collective mind of the interweb can sort this out aye?
One resource is 'Engineers Reference', oil company websites ect.
What do we want a cutting fluid to do? Remove heat? Yes. Wash out chips? Yes. Lubricate the tool tip to stop adhesine? Yes.
Lots of things will accomplish the aims some better than others.
Most materials have optimum cutting lubricants pretty well defined by now. I'm going away from soluable oil simply because I don't like the cleanup every time I use them. I don't use my lathe or mill every day and I worry about rust so based on the experience of others I'm going to try a 50/50 mix of hydrualic oil and Kerosene. I'll try some on the shaper first as that is a pure shear situation that can be arranged slow enough to observe. Early experiments suggest that this will be a cost effective solution to suit my particular needs.
 
Bob Korves said:
Cutting fluids and lubricating fluids are two totally different animals. One is to get under the metal and help it cut, the other is to keep the metals sliding on each other with a film of oil keeping them separated. Using lube oil for cutting is like using gasoline to put out a fire. Use cutting fluids for cutting, or cut dry.
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Amen, Bob! All I use in my shop is Tap Magic and Rapid Tap (the old TCE formulation) that I found on E Bay I hardly ever work on aluminum, but the modern Tap Magic works well on it and does not stink like kerosene (even deodorized kero. smells).
 
benmychree said:
Amen, Bob! All I use in my shop is Tap Magic and Rapid Tap (the old TCE formulation) that I found on E Bay I hardly ever work on aluminum, but the modern Tap Magic works well on it and does not stink like kerosene (even deodorized kero. smells).
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Thats the stage I am still at. But I do hate taking all the used oil to the recylcers every time I do an oil change. There has to be something it is good for.
 
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