Are you wanting to go to full blown pumped cutting fluid or just something to apply with a brush?

I use Morris Lubricants CORA B neat cutting oil applied by brush. I use it for machining, not tapping or dieing, steel, bronze and aluminium, brush fed on the milling machine and pump fed on the lathe.

It may not be as cheap as suds but is clean, will not damage your nice machine tool and is re-useable (if collected).

[The first sentence is a bit of a lie. Since I re-use it, the cutting oil now also contains quite a bit of ISO 32 & 68 hydraulic oil and white spirit.]

JA

On 11 December 2023 at 12:07 JasonB Said:

Are you wanting to go to full blown pumped cutting fluid or just something to apply with a brush?

Taking Jason’s question a step further, why use cutting fluid at all?

The fluid controls heat and finish, and may not be needed.

My workshop does relatively little in the way of bulk metal removal.  I’m a hobbyist who generally makes small parts from standard sized stock specifically chosen to minimise the amount of cutting needed.  For example, I prefer to use Bright Mild Steel rather than Black, because BMS comes with finished sides, that might not have to be milled at all.  My cutters have a relatively easy life, and don’t get very hot – short cuts, with plenty of time between them for cooling.

Finish also may not need fluid.  When necessary, I improve it by dabbing on neat cutting fluid with a brush, which is effective with light cuts, and helps cool the cutter.

The Cutting fluid is whatever happens to be handy, either CT90 because it’s sold by my local emporia, or a soluble oil which I got from Warco to save carriage costs as part of a larger order.  CT90 works well but it’s really for threading, and expensive.  The Warco oil is cheaper, but in neat form rather thick, and it’s really meant to be mixed with water.   Works well enough.

I also have a pump and tank system filled with an emulsion made from water and soluble oil, or ‘suds’.  This is only used when I have a serious amount of steel to remove.  Suds is an excellent cutting fluid.  Water is a first-class coolant, the soluble oil provides lubrication, and the pump provides the volume and pressure needed to wash swarf away from cutting area.  However, the mess suds makes is a serious disadvantage, so I rarely use it.  I’d go so far as to say the money spent on the tank and pump was wasted.   Not because the system is useless, but because suds don’t match my cutting needs.  Another potential problem with suds is that might go off, stink, and infect cuts.  Suds caused many amputations In the good old days before antibiotics.

I suspect most home-workshops are in the ‘apply by brush’ camp.   The brush advice assumes the cutter is HSS.  Splashing hot carbide intermittently with cold coolant is liable to crack it.  When using a brush apply coolant to the job, not the insert, or don’t apply any at all.  If carbide needs cooling, flood continuously with enthusiasm!

Professional users choose cutting fluids carefully because they remove serious amounts of metal, require good finish, and need to maximise tool-life whilst minimising power consumption.  It’s worth their while to optimise, because even small savings add up to big money.  The alloy, type of cutting operation, finish, production rate and other factors identify if a particular cutting fluid should be used.

Suds was once ubiquitous. Interestingly, industry are tending to move away from it in favour of exotica like a thin aerosol oil propelled by cryogenic nitrogen.  The main reason is cleanliness: the blast blows swarf into a collector, and the clean swarf has a high scrap value because it isn’t contaminated with cutting fluid.

Amateurs don’t have to worry about optimising – experiment with a brush and with whatever cutting fluid is available.  Almost anything oily will provide the moderate level of cooling and lubrication needed for light work. I’m not above brushing car engine oil – though it smokes a bit, it’s cheap and readily available!    I’d avoid traditional recipes though; they’re mostly bio-hazards.  Milk is an excellent cutting fluid, but it putrefies in a few hours and it’s impossible to get rid of the stink.

Dave

I have just ran out of this from Axminster from when i bought the hacksaw from them a couple years back. I have to say that i was impressed with it even a bit pricy to me. I used it in all milling /Lathe work and tapping.

https://www.axminstertools.com/ambersil-tufcut-metal-cutting-liquid-952142?queryID=2f57915adb837d963657297a1b418912

Saying that though i have just taken a gamble for the price on this.

https://www.ebay.co.uk/itm/391817355479

Its good to just try things out and see what the difference is for what you use it for.

All Best

Faffer 🙂

The always-interesting Stefan Gotteswinter often shows isopropyl alcohol being used. I don’t understand the reason behind this – is it coolant (it should work!) or lubricant (would it work?) and does it wash off slideway lubricant? Nice and clean, though…

On 12 December 2023 at 07:09 Kiwi Bloke Said:

The always-interesting Stefan Gotteswinter often shows isopropyl alcohol being used. I don’t understand the reason behind this – is it coolant (it should work!) or lubricant (would it work?) and does it wash off slideway lubricant? Nice and clean, though…

I use iso-propyl alcohol on my CNC when machining metals (aluminium especially). It definitely acts as a lubricant and substantially improves the surface finish. The quantity I use is tiny, however – just a drop every few seconds applied by a non-atomising air jet. The IPA has dried before it has a chance to get more than a few inches from the cut. (There aren’t any exposed slideways on my CNC, anyway). It’s a lot cleaner on a machine that is used for a mixture of wood, plastics and metal. I don’t think I’d use it on a manual mill.

Air used to clear swarf will not send it everywhere. Take a look at this flywheel cut at the weekend from solid CI, just about all the chips are in the fairly minimal tray and only a tiny bit on the bench at the side. All cut with air on to clear swarf plush a couple of blowing downs when changing tools and work position.

It really depends on what the OP wants the fluid to do – Cool, Clear swarf or improve finish? As I said I’m doing more cutting dry even HSS gives a decent finish dry. Neat oil would tend to clog the cutter and you then run the risk of recutting the swarf which effects finish and tool life so may as well go dry and let the swarf clear itself.

I use a generic soluble oil from the local oil and grease merchant. I dilute it anything from 10-20:1 and use it on a Colchester lathe, Harrison mill and Qualters power hacksaw simply because these machines have the facility to pump coolant over the workpiece. It seems to work fine for me but I have been known to do a lot of machining ‘dry’ because I am hardly into industrial production rates in a back shed workshop although these machines can really chew through metal when you want them to. I accept that some people cannot tolerate the thought of anything containing water anywhere near their cherished machines but it does leave an oily residue on exposed surfaces which is a good deterrent to the rust fairy for those who suffer condensation problems. It would not suit those whose workshops resemble a laboratory in terms of cleanliness because it can be messy at times but my workshop is always somewhat ‘lived in’ with swarf etc. in nooks and crannies so it really doesn’t matter to me.