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Rapeseed oil as cutting oil, NO!

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Skarven16/05/2012 18:56:17
93 forum posts
11 photos


I have been using rapeseed oil as a cutting oil on my lathe and mill for about 7-8 months, and beeen very pleased with the performance. This was discussed in another thread some time ago.

However, the sceptics were right, it started to smell a little, not a really bad smell, but....

The worst thing was not that it started to leave a gummy sort of residue. This was easily removed by some WD40, but I suspect that the oil also had absorbed some moisture , because under my tailstock, which had been standing in the same place for quite some time, there was a black corrosion mark on the ways, even if there was plenty of oil. I could not feel it with my nails, but it was there! I could almost remove it with one of the sponges with a hard green side, but not quite.

Now I'm trying out water soluble cutting oil smiley

The finnish with rapeseed oil was better than with the new one.thoughsad

Clive Hartland16/05/2012 22:36:04
2284 forum posts
38 photos

I remember sometime reading that OSR oil has to be processed to take out any acidity, it is used for foodstuff and mixing with other oils.

Perhaps you had raw OSR and have now reaped the benefit!

Using it must be like 'Frying tonight' and the smell must be like rotting cabbage as it comes from the Brassica type plant family.

The fact that the stain is still there after cleaning means its etched into the metal.

I do find that WD40 leaves a waxy deposit which catches dust quite well if left to dry out!


Stub Mandrel17/05/2012 21:07:23
4305 forum posts
292 photos

You have discovered the joy of anaerobic bacteria which love any interface between oil and the tiniest amount of moisture.

I used to know a chap who had worked on the problem at Porton Down(!) in the 70s with regard to fuel oil in storage tanks.


Deltic00717/05/2012 21:29:27
130 forum posts
12 photos

Lesson learned me thinks.Best get some proper stuff and give your machine a good clean out.

Hope it goes OK


Boiler Bri18/05/2012 03:49:51
652 forum posts
306 photos


My company manufactures filling machines for all types of vegetable oils. In time you will find that the oil will leave a wax on everything that it touches. It will form like old varnish and takes a hell of time to clean off. If left long enough bacteria will grow and it will turn into a hard gel which is pretty awful. If you have any small bore tubes it will clog them up, in fact it will clog every thing up.

I know that coolant is pretty costly for the home user, but it is worth every penny.

We use a product made by Batoyle now. It is mixed at 20% and looks opaque. The benefit of it is that does not smell like the old stuff used to.

If i remember i will ask the guys what it's called.



Clive Hartland18/05/2012 10:01:16
2284 forum posts
38 photos

It seems that the OSR plant has been genetically modified and the resultant oil is now called 'Canola Oil' (Canadian Oil Company)

OSR (Original) has a high Erucic acid content and the effects have been noticed in lab rats that it causes lung cancer and can also cause heart lesions.

The Canola oil is very low in Erucic acid and is edible but is not suitable as a cutting fluid.

Some commercial cutting fluids are vegeatable based but have additives to keep them clean. Most are used as spray coolant and mixed with water.

For smaller applications then you can use one of thos aerosol cans of oil for misting a frying pan.

Mainly used when machining Alu. and Copper and for tapping threads.

Various other oils are quoted such as castor oil and Peanut oil. Sperm oil is also quoted but is wasted on coolant as it is a superb quenching oil.

What ever is used like this is expensive so a normal aqua mixed coolant is best as it is inhibited and has a long life and is replaceable easily.


Skarven19/05/2012 13:57:04
93 forum posts
11 photos

Hi all,

sorry for late response, been away...


"Perhaps you had raw OSR and have now reaped the benefit!"

No, the one I used was the Canola Oil low Erucic acid variant normally used for cooking.

"Using it must be like 'Frying tonight' and the smell must be like rotting cabbage as it comes from the Brassica type plant family."

In fact, the smell wasn't really bad. The problem was the gumming and the corrosion.

"The fact that the stain is still there after cleaning means its etched into the metal."

Yes, it is very little though, I can't feel it at all with my nails. I'm going to try some metal polish.

The main reason for using rapeseed oil was the fact that it was non-poisonous, and it was very easy to vipe off your hands.

I'm using the water soluble oil type now, but it has a few drawbacks: All of this is on the mill, I have not used it on the lathe yet.

It does not smell good. This is according to my wife. My tolerance for "machinery" smell is very high!

The very low viscosity makes a real SPLASH every time you start the pump and the fluid reaches the nozzle. This splash spreads oil far from the machine! It is easy to clean up though.

The surface finnish is not as good as it was with rapeseed. I suspect that this is also a result of the low viscosity?

I have the impression that the thick rapeseed oil had a dampening effect. It seems to me that I more easily get chatter now.

If I can lay my hands on a can of neat cutting oil, or a mineral, what we used to call winter oil (10W), I will try to use that. The problem with the cutting oils is that they all contains additives which are more or less poisonous. My biggest problem is that I have been unable to get either!

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