Cutting oil vs Old motor oil and non-detergent oil

woodchucker

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The other night I had a conversation with a friend. He's a gunsmith, his dad was a machinist. We were talking about my mill.
He said I should not use SAE 20 for the 8520, that I should use non-detergent 30 wt oil, that detergent will corrode the mill. This I believe to be true, but just checking is he correct.

in relation to both mill and lathe
He said to forget the expensive cutting oils. I have been using tap magic for AL, and Oatley dark for steels. Some times if I have a difficult to cut stuff and have tried gear oil to get a cut and it's been a help. Not sure why, just tried it.
Anyway for the AL he said only use kerosene, which is cheaper. I have known guys saying that, so not that far off.
The old motor oil surprised me. He said used motor oil cuts better than the normal chlorinated cutting oils. Aside from the stink of having used motor oil around, is this right? Anyone here feel the same way?
Next project, I'll give it a try.
 
if the 20 wt oil was non detergent there would be little argument- they are basically the same oils except for the viscosity
if the 20 wt is detergent oil, that is a slightly different animal- detergent oils are made for internal combustion engines with filtered oil recirculating systems.
the detergent oils tend to suspend particulates, non detergent oils tend to shed particulates
you wanna use non detergent oils for lubrication purposes , for best results and longevity

i machine a lot of things dry,
i'm not a big fan using lubricating oil for milling and turning, although i have done it many times
generally i use Anchor Lube for stainless steel,
for other steels bacon grease/mineral oil blend, i do have some sulfurized oil but i don't like to use it much- its vapors stink badly in use
for AL3- i like to use old school tap magic, or kerosene, or a kerosene/bacon grease mixture
bacon grease is cheap, abundant at my house, and works wonders on quite a few different materials.
there are superior industrial formulations- some can be quite expensive

i'd suggest trying anchor lube for steels and stainless- it does work on aluminum,
i haven't tried it on bronze or brass- but i expect it would suffice in a pinch
 
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I use Anchor Lube as well. Most of the time for threading steel I use just about any oil that is a hand. Aluminum I use kerosene or WD40 which has kerosene as a major ingredient.
Pierre
 
I use Anchor Lube as well. Most of the time for threading steel I use just about any oil that is a hand. Aluminum I use kerosene or WD40 which has kerosene as a major ingredient.
Pierre

I use Anchor lube and water it down and dip the tap and don't flush it all over the component


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I would be hungry all the time, machining at your house Ulma Doctor. Nothing like the smell of cooking bacon:big grin:
Cheers
Martin
 
Used motor oil is good for stuff like case hardening(outside) but not something I would use for machining. It would be hard to keep the lathe clean and carcinogenic if you handle it much... :eek:
I use sulfurated oil for threading on steel parts and gladly machine parts dry if possible. :) Of course there are a few times I do flood cooling and heavy machining and need to vent
sorta like Fukushima.....:grin:
 
For Aluminum I use WD40,any penetrating oil that can be found at yard sales for a buck a can. Aluminum does not need much, just something to make the edge "dirty" so it does not gall and weld. Dark threading oil for steel, or any samples I might be able to be talked into trying. :) Notice the trend?
 
for AL3- i like to use old school tap magic, or kerosene, or a kerosene/bacon grease mixture
bacon grease is cheap, abundant at my house, and works wonders on quite a few different materials.
I forgot he did mention bacon grease.. but in my mind that would get rancid w/o refrigeration ... NO?

So the question is not what you guys use, but is the used motor oil that good. He claims it's great.
I am not spending on anchor 2x the price of regular cutting oil, I'm too cheap, would rather buy metal, or tools :)
 
Honestly if you want to use motor oil as cutting oil, a 2 gallon jug of SAE20 (roughly equivalent
to ISO68) non-detergent motor oil goes for around $20 at TractorSupply. Not as cheap as used
motor oil, but you can use this to lubricate your mill or lathe as well. For my lathe and mill gear
boxes I will still use Mobil DTE Heavy/Medium (ISO68), but I have used the SAE20 to flush out
my lathe gear box once. The oil from the factory got really black after break in and I didn't want
to waste the more expensive Mobil oil only to get that fouled up too. I used the SAE20 for a few
weeks, then drained it, and then refilled with the Mobil.

To me the new clean oil is nicer to work with and makes less of a mess. If I wanted to quench after
hardening, or to oil blacken a part, used motor oil would probably be the way to go, but as a
cutting oil, I'm sure it would work, I'm just not a fan.
 
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