DTR,
If it helps at all I agree with the above comments. I have no coolant pump on my little lathe but just brush on, also when tapping threads, reaming, etc, on the bench. When first starting I used soluble oil (suds) because that was all I knew, but as others have said, as it gets older it tends to stink a bit (my workshop is in the cellar) and is particularly so if you don't use it regularly like me. And it wasn't so cheap either.
So looking around I found a synthetic here (Switzerland) called "WS-101" that's made by a local Swiss company. I bought 5 litres and it certainly wasn't cheap (about equiv of 30 or 40 quid I seem to remember) BUT it's watered down 10:1 (with ordinary tap water) and that 5 litre can will last me literally years. I doesn't rust the machine ways or anything else, works very well on all sorts of metals (even helps a bit to reduce that awful "squawk" on hard brass), and has no smell at all - my 1st mix is now about 2 years old.
About the only drawback I can see is that before dilution it's a fairly reasonable green colour but after dilution (I just put 1 litre into an old plastic soft drinks bottle) it looks just like Roses Lime Juice Cordial ;-). So just to be sure, and even though we don't have children or pets I've clearly marked the bottle "Poison" (which according to the manufacturer it is).
I shouldn't think this Swiss stuff is available in UK but Arc Euro Trade Ltd (with whom I have dealt several times with complete satisfaction - usual disclaimers) have something which sounds pretty similar to my WS-101 in their catalogue but as above, I haven't tried that one. It's called "Rockoil Maxcut 5"
LINK:
http://www.arceurotrade.co.uk/default.aspx
For working ali I usually use aviation fuel (paraffin - kerosene) because I can often get it easily, but any type of paraffin or thin "oil" such as central heating oil will do - you really only need it to stop/slow down work hardening of the job and to keep "blobs" of ali from building up on cutting edges.
Recently however tools stores here have started selling WD40 in 10 litre bottles (with a "free" plastic hand pump spray applicator bottle) and the price works out much more reasonably than the usual WD40 aerosols. I don't know if that applies in UK but if so I've found WD40 very good for ali work when I couldn't lay my hands on Jet A1 immediately.
Some people do complain about WD40 leaving a brown residue on machine ways etc, but personally I've never had that problem - perhaps because, as above, my workshop is in the cellar and no matter the outside temp it never gets below about 10 to 12 degrees C in there.
Hope that helps, sorry for delayed response.
Best of luck
AES
I clean my decking with it.
