Cheap Oil for hardening

Hi Guys,

Don't want to give the game away on my being tight but I have just taken receipt of a piece of oil hardening gauge plate (1/4 inch square). It is O1 so needs oil hardening. it will be about 2 inches long when made.

Anyone recommend a 'cheap' oil that will suffice for hardening this?

Regards

Chris

Cheap cooking oil from Aldi? Old engine oil?

Rapeseed oil works well, but will get thicker with each use until it is like golden syrup.

Funnily enough for small parts I use a half-full golden syrup tin, as you can use the lid to stop the smoke/extinguish any flames.

Do work outside, it's a smelly business.

Used engine oil can be heavily loaded with carcinogens, you don't want to inhale that smoke.

Rapeseed oil works for oil blacking as well.

Neil

The correct oil comes from sperm whales but that is probably unobtainable (thankfully) but I have used old engine oil in the past.

You need to make sure that there is plenty of oil to avoid it bursting into flames when you dunk the item into it.

It is impossible to give an idea of quantity because that will depend on the size of the item but assuming that you are hardening small clock parts or tools then 5ltrs should be plenty.

Be careful with the oil as I'm sure that I've read somewhere that it can be carsinogenic.

Brian

The cheapest oil would be whatever you have kicking around the workshop already. Or a large cupful of cooking oil from the kitchen - it's free.

The British Tubal Cain warned against old motor oil for quenching because he said it can contain up to 15% petrol. I suppose it's possible. Engine oil is smeared over the cylinder walls by the piston rings, and then petrol and air squirted in and the whole lot compressed. I guess some petrol could dissolve in the oil, survive the burn and end up back in the sump where it might accumulate.

But I've never heard of an accident due to old engine oil flashing off. Could it have been a problem when Tubal Cain was a lad due to manual chokes, plain oils, plus low tolerances and compression in early car engines, and isn't an issue today?

Dave

I just went to local car spares and bought cheapest engin oil. I pour it into an old deep fat fryer tank and when finnished pour it back there is a spout on fryer tank to make it easy. You need quite a lot of oil to quench the gauge plate quick enough and move it around vigorously when plunged into oil.

David

Had not yet heard of blackening steel so looked it up. Could be useful.

Thanks Neil and all for posting

Fuel in engine oil is a real problem. A particular case is modern diesels with particulate filters (DPF) some designs (Fiat, GM) inject diesel on the exhaust stroke to regenerate the DPF and some washes down the bore into the fuel. This can give a noticable increase in oil level.
A cheap oil with minmal additives would be good. The oil volume compared to metal mass will affect the temper. So will the oil temperature. Pre-heating the oil with hot scrap is sometimes done for critial parts.

No, that’s part of the fun!

The oil quench at tech held a few gallons of oil, a friend discovered that a 20mm red hot bar could be plunged in to vaporise the oil and the quickly pulled out while still hot enough to ignite the vapour cloud, this was highly entertaining until the instructor appeared round the corner

Mike

Heat treat was one of the many hats I used to wear, I would use a cheap engine oil from say Wilko, clean oil with no contaminants is the way to go.

Tony

I use Quenchall 22 oil which is formulated for the job.

I bought 5 litres many moons ago and it is still going strong.

According the the blurb it is very much like a hydraulic oil in terms of viscosity and high temperature capability.

It never flashes off and doesn't get thicker over time.

Was not as expensive as motor oil if I recall.

Mick

I use Nuto 32 oil from/for the lathe for hardening and blacking. It is cheap (if bought in sensible amounts), clean with very few additives and I have plenty of it.

JA

Edited By JA on 23/09/2020 08:18:24