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What Cutting Fluid to use?

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Men Ifr10/11/2017 17:27:32
73 forum posts


What cutting fluid would be best to look at using for my milling machine - hopefully one fluid will do plastic steel and alloy.

It would be preferable to get it mail order as well.

Men Ifr10/11/2017 17:30:01
73 forum posts

I am thinking of flood cooling albeit with a very small flow rate rather than something you apply by hand...

David Standing 110/11/2017 17:46:28
1005 forum posts
41 photos

On the basis that the best lubricants for aluminium if you don't machine it dry (and certainly the most cost effective) are paraffin or WD40, and they won't do for steel or plastic (but many plastics are machined dry anyway), then by default it is basically a no.

If you want to use flood coolant, that's a totally different question!

Google is probably your best friend.

SillyOldDuffer10/11/2017 18:01:48
2793 forum posts
563 photos

I use neat cutting oil for flood cooling rather than a water emulsion. The idea is that neat oil won't cause rust and it's good for steel and Aluminium.

However, I only use the pump when taking repeated heavy cuts with HSS because even trickle cooling is hellish messy. Most of the time I just use a brush or spray. Buying a flood cooling system was my single worst investment!

Not sure about plastics; cutting oil might stain or attack them.


BDH10/11/2017 18:02:26
732 forum posts
66 photos

Following a recommendation on here some time ago, I use Castrol Alusol which was formulated for aluminium but is also suitable for steel. Not sure about plastics though.

I bought a 1 ltre bottle on ebay (but the label has washed off so I cannot tell you where from).

I can be diluted about 20 to 1 but I use it at 10 to 1 and have had no problems with corrosion or staining and you can see the work through the liquid.


ChrisH10/11/2017 19:36:05
757 forum posts
12 photos

Like Dave (SillyOldDuffer), I also use neat cutting oil on the mill, from Warco in my case. I have a flood coolant system but use it from an oil can at present as, also like Dave, I find flood coolant ends up being splashed everywhere; I need some guards making to contain the mess onto the table - another job to do on the "to-do" work list! I have also (yet again like Dave!) wondered if I spent wisely buying a flood coolant system, but as it was on a 'special offer' and under ££100 and a few years ago now it's now a case of "oh well.....", money well gone and out the budget now and forgotten!

However, I do find that use of flood coolant/cutting oil is a great help when milling steel both in getting a good finish and getting the swarf out the way plus helping extend tool life, I use HSS tools. Just my experience on my machine.


Muzzer10/11/2017 20:30:41
2725 forum posts
439 photos

Following Andrew Johnston's recommendation and my own brief research, I got some Castrol Hysol (water soluble). It's recommended for both steel and light alloy with little danger of corrosion. You use it at about 7% concentration. The main drawback is the MOQ of 25 litres but you may be able to buy a litre from ebay or similar. Works nicely, smells OK and doesn't seem to go off (one of its claims).

Cools HSS and stops loominum sticking to the tool.


Jeff Dayman10/11/2017 22:55:56
1187 forum posts
31 photos
Posted by Men Ifr on 10/11/2017 17:27:32:


What cutting fluid would be best to look at using for my milling machine - hopefully one fluid will do plastic steel and alloy."

Be careful with oil or solvent based cutting fluids on plastics - many plastics will crack or craze with exposure to oil.

A small compressed air jet is often good when machining plastics as a cooling method, just direct it at the cutter end. Keep speeds down and use sharpest possible cutters when working thermoplastics. If there is too much cutting friction or rubbing the thermoplastic may melt , stick to the cutter, cool and re-harden, and jam things solid.

Raymond Anderson11/11/2017 07:38:25
694 forum posts
132 photos

As stated by others, Castrol. You have a choice of 3 Alusol A [ which used to be known as Hysol Excel] or Hysol 40 and Hysol XF. I have used the Excel [ Alusol A] for years and it is the bee's knees. Never fouls smells, never any staining or rusting. AND lubricates the ways very well. I think there is a lad on e bay that's sells Excel in 1 litre bottles, or else the minimum is 20 litres. Ps, the lubrication properties are NOT a substitute for Magnaglide but used in conjunction.



Edited By Raymond Anderson on 11/11/2017 07:40:14

Michael-w12/11/2017 13:33:16
2017 forum posts
49 photos

I just use this stuff **LINK**

For my intents and purposes i'm quite happy to go without flood coolant having tried it.


A little bit of neat cutting oil does help the tool, I find, and I don't end up in a state afterwards.

Good idea to deposit it in a little container with a brush beside ​it.

Michael W

Edited By Michael-w on 12/11/2017 13:34:45

mechman4813/11/2017 13:03:01
1942 forum posts
363 photos

... A little bit of neat cutting oil does help the tool, I find, and I don't end up in a state afterwards.

Good idea to deposit it in a little container with a brush beside ​it

Michael W...

​Along the same lines here's what I use...

cutting fluid pot location..jpg


Men Ifr14/11/2017 17:24:04
73 forum posts

Thanks all for the replies I've ordered 1L to try out, I think the trick was to search for 'water soluble oil'.

I have an oil pot but looking to see if (very small amounts) of flood coolant work better, I have something like this:

I found with an air supply it makes a huge mess however if I turn off the compressed air and position the fluid contained above the nozzle I get a steady stream of maybe 1=2mm diameter water - a small amount but probably a huge improvement on nothing in terms of cooling - anyway I will give it a go.

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