lathe tool cutting oils

i dont think its water after its mixed as it turns into an emulsion

I couldn't possibly comment on the foolish part, but it is a prejudice.

I use water soluble oil flood coolant on all my machine tools; lathes, mills and grinders. I don't have a problem with rust. However, there is a caveat. The percentage mix of oil and water needs to be correct. As I know from experience if the mixture is too weak you will get spots of rust. When I top up the coolant I use a refractometer to check the mixture strength. I aim to be in the middle of the manufacturer's recommended range, 7% if I remember correctly for my coolant.

Andrew

Andrew, is your refractometer something like this one?

**LINK**

Thanks

Nige

Thanks Andrew! I suspected it was a prejudice. It's truly foolish because despite being suspicious I couldn't be bothered to check and bought neat oil. Not only is it expensive, cutting oil might not be as good as a water emulsion at removing heat. Never mind, as mistakes go it won't break the bank. I'll switch to emulsion when it runs out.

Dave

I only tend to use lubricants when drilling on the lathe or for final cuts. I use soluble oil in a hand spray. For tapping I use tapping compound, can’t remember the make but it smells quite “organic”! As said slitting saws benefit from a lubricant so I use suds again in a spray bottle.

That's the sort I've got. Seems a good price. Like Andrew, I use Castrol Hysol at 7% and I check it with one of these boys.

Very simple to use. Put a small droplet on the flat angled face, drop the flap down onto it (so the drop wets both surfaces), hold it up to the light and simply read off the value.

There are different versions for different applications and we want % of oil in water, not composition of (beer) wort. Obviously, the refractive index with 7% oil will be different to that of 7% sugar content. so make sure it is for the correct application - cutting fluid, not glycol coolant etc.

Murray

Muzzer beat me to it, but yes. I bought mine from Index Instruments as they're fairly close to me, near Huntingdon. It cost rather more than the Ebay one. However, to reiterate what Muzzer says they come in a wide selection to cover different liquids and ranges. Mine is specfically for cutting oils and covers the range 0-18%.

Andrew

Andrew,

I have some queries for you please, if you don't mind answering?

1. You mentioned refractometer from Index Instruments, specifically for cutting oils. Did you mean this one.?

2. You mentioned that you use Castrol Hysol XF. Looking at the Technical Datasheet, it shows a Refractometer factor of 1.1. If the refractometer is the one which is shown in my point 1 - calibrated in % from 1% to 18%, does it mean that the 7% on the scale is 7% concentration, or, more like 7.7% ? i.e. Refractor Factor of 1.1 x 7% on the scale?

Ketan at ARC

Edited By Ketan Swali on 21/12/2017 16:59:44

It might be best to calibrate a refractometer when you first get it by mixing up an accurate sample of coolant so that you know what reading corresponds to the concentration you want to use.

1. Yep, that's the one

2. The concentration is theoretically the refractometer reading times the factor, so if I read 7% the concentration is actually 7.7%. However, tramp oil reduces the factor, and since I don't have tramp oil collector I suspect my actual concentrations are a bit lower. As long as I'm around the 7% mark give or take a percent I don't worry too much. I'd rather be a little high than low. I don't measure that often, months apart, although more often in the summer as evaporation is greater.

Andrew

Noted Mark, simple, and good point, thanks.

Good to see you on here. Haven't seen you for a while. Pop in when you get a chance, specially now that you are retired.

Ketan at ARC.

Andrew, thanks for the clarification, much appreciated.

Regarding 'tramp oil', I am presuming you mean a mixture of 'contaminants', and if so, I understand.

Ketan at ARC.

Correct, although in my case I suspect it is mostly slideway oil. The tanks have a patchy thin film of non-soluble oil floating on top. Since I don't use my machines 24/7, and don't generally need to dispose of coolant, I don't worry about removing the oil as the commercial machine shops do.

In theory the cylindrical grinder will have fine grinding dust in the mix, but the grinder has a couple of settling tanks built-in before the coolant exits to the external storage tank. So I suspect the coolant proper is fairly clean. I understand that dirty coolant can cause inconsistent finishes when grinding, and I don't see that.

Andrew

Thanks Andrew

I will try anything out so far i havent found a distinctive coolant that offers any benefit over any others for the work i do.
Had various forms of Morris, Smith and Allen and others, just finished off 25ltrs of Castrol Hysol XF now running weak.
Also tried a couple of the synthetics did a decent job but always had that niggly doubt it looked opaque and weak. Those of us used to the conventional stuff would be reaching for the refractometer hourly, just looks like a too weak mix opaque with a tint of colour.

My old 140 Wallace had a removable mesh level with top of coolant tray. Below about 7" x 5" x 6" deep trough coolant fed in to of which coolant outlet was about 2" high, No such thing on the newer M series just clean tank out once a year if used daily with brute force.

Fears of corrosion due to left over suds aren't completely irrational. In my experience most likely where there is little clearance and little ventilation so the water content doesn't evaporate from under the oil film allowing corrosion to occur.

For example my Smart & Brown 1024 has a couple or three square inches of corrosion pits on the flat portion of the bed behind the front Vee ways. Clearance between saddle and bed is maybe 20 thou in that area over what appears to be something like 10 to 20 square inches. After using flood coolant you need to work quite hard to get all the coolant wiped off the bed in that area. Usually takes 5 or 6 passes of the saddle to get it all swept out wiping up after each pass. Having cleaned off I always anoint with way oil to help keep things clean. Not an issue where the saddle runs because the 1024 has an efficient and effective pump system feeding from the apron. If its as good at the lubrication bit as it is at the apron emptying task its an excellent system.

I use Rocol Ultracut synthetic at the specified lowest concentration as a coolant. Seems to last forever without going off in the tank. For my use lubrication is more important than cooling so I have Bijur spranymist systems on the machines too. Main problem with those is getting them turned down to reliably deliver the correct, tiny, output. I'm certain most users set output of mist systems far too high hence the fug'n smell issues. Proper level is barely enough to put at wet stain on ordinary copier paper after a minute or so. Even that tiny amount is very effective. Need to regularly clean collets and chuck jaws because the build up of synthetic lubricant seriously reduces grip.

I generally work dry at 50 thou / 1mm roughing cuts and 20 thou / 0.5 mm finishing which keeps down the mess and seriously reduces the hassle of dealing with swarf'n chips.

Clive.

The only time i get rust is when the coolants way too weak.

Its ultra rare i clean machine down time is money, certain jobs i use the coolant to wash the machine down after.
Certainly with the Castrol left as is after jobs done, water evaporates leaving pure oil. Winter needs daily top up about 0.5 to 1ltr a day, summer 2 to 5 ltrs a day with a good 80% water evaporation, the other 20% is losses.
Similar was with a synthetic i tried tempted to try again if i can get my head around the lack of emulsion look.

I use now mostly rice bran oil from a spray can. Castor oil I still use for tapping, but does leave a nasty gum to clean up from if not cleaned with meths or some other solvent. SO now clean up more often as these oils tend to go gummy over time. Soluble coolants get into the slides etc and I feel is the main cause of wear in machine tools. Machines that have cutting oil coolant, tend to last a lot longer and in better condition than those machine that use water based coolants. Castor is great for tapping holes and I find the tap and reamers cut closer to size with castor oil over anything else I have tried over the years. I buy the degummed castor oil from model/honny shops for those that make their own fuel. I don't get the castor and synthetic mix.

Neil

Entirely hypothetical so would any other form of liquid or non liquid.
Used to part own a precision engineers one part was rebuilding machines, can tell you all about oils, lack of oil, grease etc and its affect on slides. I dont think you will be able to find anyone that can categorically confirm, exactly the same jobs and same time etc spent has to be compared on exactly the same machines.

Look on the brightside any coolant or oil will wash debris away.