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Using coolant

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Dennis Lowe17/07/2013 10:00:32
2 forum posts


I am retired and setting up a workshop for model engineering having had little previous experience in this area. I have a Myford S7 long bed which I acquired some while ago in anticipation and have started refurbishment.

The lathe came with an old non working coolant system and I am not sure whether this is necessary for amateur use in a non production environment. I understand that leaving coolant in the tank for lengthy periods should be avoided.

My question is that under what circumstances is it recommended?

Any advice would be very much appreciated.

Trevor Wright17/07/2013 12:56:25
139 forum posts
36 photos


I run my lathe dry and use WD40 from the can if wanting a good finish cut.

Having spent years covered in coolant off various machines and the smell when cleaning down said machines.....I didn't want my garage to get that dirty.


Andyf17/07/2013 14:59:36
392 forum posts

When I actually use it, I apply coolant sparingly with a brush. I got tired of getting go-faster stripes up the front of my shirts.


Thor 🇳🇴17/07/2013 17:03:35
1605 forum posts
45 photos

Hi Dennis,

Like Trevor and Andy I don't use a flood coolant, For a nice finish I too apply coolant with a brush or similar. If you use emulsion as coolant you should clean the lathe afterwards and oil it. My experioence with emulsion is that if you leave it you get stains on slideways.


Rik Shaw17/07/2013 17:24:53
1480 forum posts
398 photos

Hello Dennis - See how you get on first by just using a small brush with cutting oil. If you are only doing the odd job now and again it may suffice. I have used Rotabroach cutting oil from Ebay - about £8 a litre (lasted me 18 months or so.) All that though was on a small mini machining centre.

I recently acquired bigger machinery and in the last week have installed a WARCO coolant system (the expensive one as the cheaper ones are out of stock). I have filled the system with WARCO "NeatCut" oil and it pumps OK.

I am using oil as a coolant because I do not like the smell of mistic. It will also help the machinery from becoming rusty. Using coolant - oil OR mistic/suds will stop your tools from becoming blunt to quickly - important if you are cutting a lot of metal, your finishes may also be superior depending on what you are machining. Not having to hold a brush frees up a hand and allows more control of the lathe handwheels.

Hope this helps.


mechman4817/07/2013 19:05:30
2947 forum posts
468 photos

Hi Dennis


I tend to cut dry & only use WD40 on aluminium, I don't do a lot of machining at the moment..well not yet any way, & then only been small stuff & then only generally use my tangential tool for 90% of any turning,the other 10% I use insert tip tools, so applying neat cutting oil with a brush tends to suffice for my needs.


Alan .20417/07/2013 22:59:57
304 forum posts
14 photos

I have a tub high enough i can just reach (plastic pop bottle cut in half) filled with soluble cutting oil a line down to the lath with a tap on it and just use a drip feed, works well but i will fit a powered coolant system in time but the gravity drip feed is a good way to start, a friend of mine has been doing it this way for the last forty odd years that must mean something.


stevetee17/07/2013 23:45:26
144 forum posts
14 photos

For the home workshop mystic is just not worth it, the emulsion inevitably goes sour, smells foul and all needs to be cleaned out and replaced . Also its not required for machining cast iron , brasses, ally , just for steel. I think Alan.204 has the right idea, a slow drip feed.

NJH18/07/2013 00:58:22
2314 forum posts
139 photos

Hi Dennis

I use Neat Cutting Oil, when required, applied from a 250ml squeezy bottle purchased from ebay, Try going there and entering "250ml wash bottle" in the search box. I bought 2 at 99p each and they were delivered post free - from Bankok! The "squirter" tube with the right angle bend is rigid and better, I find, than the more usual lab squeeze bottle with a flexible spout. No problems with staining etc using Neat Cutting oil and an occasional well directed squirt does the business.


Andrew Johnston18/07/2013 11:50:38
6575 forum posts
701 photos

I use a soluble oil for coolant, Biokool14 from Hallett Oils. It seems quite happy sitting for months, or years, without going sour.

I use coolant on my machines as follows, with the proviso that brass and cast iron are normally cut dry:

Lathe: I mostly use insert carbide tooling and cut all materials dry; coolant is only used with HSS tools, mostly drills

Repetition lathe: I always use coolant, mainly to wash away swarf, although all tooling is HSS

Vertical mill: Carbide cutters run dry, for HSS I use coolant if it involves heavy cuts

Horizontal mill: Mostly HSS cutters, so I use coolant

CNC mill: I always use coolant, irrespective of cutter type, to wash away swarf, escept for cast iron

Cylindrical grinding: I always use coolant

All my machines use flood coolant, I just can't see the point of the occassional 'dab' of coolant. Think about the numbers. Let's assume we have a 3/4hp motor on the lathe and we're running a decent depth of cut and feedrate. So we might be consuming about 500W of electrical power, let's say 450W of useful power allowing for losses in the headstock. Most of the 450W is going to end up as heat, ideally mostly in the swarf, but some in the tool and workpiece. Now 450W is equivalent to 450J/sec. So each second we need to get rid of 450 joules. The specific heat of water is about 4.2 joules per gram per degree. Let's assume we want to keep the coolant temperature rise to 30°C, we don't want to boil it away. That means we need 3.57 grams of water per second or 214 grams per minute. One litre of water weighs about 1kg. So 214 grams is 214 millilitres, or about 0.38 pints. That's a lot of dabbing!



Dennis Lowe18/07/2013 21:50:49
2 forum posts

Thank you to everyone who has given advice. Very helpful.


Muzzer18/07/2013 22:00:55
2904 forum posts
448 photos

One of the benefits of WD40 apart from its (relatively) limited cooling effect is to lubricate the tool and its cutting edge. In many cases the surface finish is visibly improved, so you might reasonably deduce that the action at the cutting edge is being affected for the good and the power consumption / heat generation is being reduced.

Obviously this would only hold true when the tool and workpiece are below the temperature at which WD40 ceases to be - but for many of the operations described, that's probably valid..

For larger and longer duration jobs, I use the coolant in the certain knowledge that if I don't, the tools will soon lose their edge and need to be replaced or resharpened before the work is completed.


Stub Mandrel19/07/2013 20:05:06
4315 forum posts
291 photos
1 articles

Not sure I want to inhale overheated WD40 fumes.


Ian S C20/07/2013 11:33:56
7468 forum posts
230 photos

I use soluble cutting oil in a 250 ml squeeze bottle, it was a bottle of PVA wood glue. Ian S C

Rik Shaw09/01/2014 17:37:20
1480 forum posts
398 photos

Just an update to my post re: my oil coolant flood system. Having used the pumped NEATCUT oil for some time, I have in the last few days driven the lathe quite hard on some tough nickel steel and I have to come clean and report that I have found the system wanting - why? - SMOKE!!!>>

I found that that by only putting on a 2O thou deep cut and flooding the job I generated clouds of thick oily smoke which was enough to make me vacate the workshop after just one pass.>>

The alternative I found was to machine with no coolant. Bear in mind that the stuff I am turning is as of "old boots" and that I am using carbide insert tooling it comes away from the job viciously blue and still creates smoke when it hits the oily swarf tray anyway.>>

My wife showed me some of my laundered socks today complete with small holes where the top of my foot would be, I muttered "moths" but got a funny look back.

>Looks like all tough stuff from now on will have to be dealt with the workshop door wide open regardless of outside temperatures. All along though my kit stays rust free - I can live with that.>


Graham Wharton09/01/2014 19:27:17
149 forum posts
48 photos

Rik. The fact you're getting smoke suggests the coolant in contact with the cutting edge is getting too hot and burning. You're only going to fix that by generating less heat, or throwing more coolant at it to keep the temperature down. I notice that neatcut stuff is advertised as a neat cutting oil, not a machining coolant.

No connection to the seller, and presumably the high price means he is out of stock, but I use this stuff. It dilutes down with water, turning into an emulsion. You can make plenty up from a 5L tub. Lasts a long time, doesnt stink too bad and stops your machine rusting if you spray it everywhere (not good if you want to keep your machine nice and clean though.... My lathe is one of the dirtiest places known to man due to a combination of coolant everywhere and the occasional spraying of cast iron dust/swarf)

Yesterday I was taking 60 thou cuts on my C6B on mild steel flooding with coolant and wasn't getting any smoke whatsoever. I do have full guarding in place over the chuck so I can really chuck coolant at it and it doesn't go everywhere. If i was going to make the same cut and just dab some neat cutting oil on from a squeeze bottle or low feed from a coolant system, then I'd expect alot of smoke too. I'm probably applying in the region of 1 litre of coolant every 30 seconds when I properly flood coolant. How does that compare with the rate coming from your system?

Like Andrew said above. When you're generating alot of heat, you need a lot of fluid to take that heat away. A small amount of fluid is just going to burn and ultimately give you smoke.

I see that Neatcut oil is used neat and not mixed down with water.

Hope this helps


Rik Shaw10/01/2014 08:59:17
1480 forum posts
398 photos

Graham - thank you for commenting. I would love to increase the flow but the viscosity of the oil is such that it would overflow the swarf tray before it manages the return trip via the gauze chip trap. I agree that soluble oil (mistic) works MUCH better as a coolant but would bring its own problems for me anyway in the form of rust (I have tried it so I know). My workshop is an uninsulated garden shed and I know that my machines and tooling would suffer using soluble oil coolant.

For me, using oil is not a perfect solution by any means simply a compromise, looking at my shiny tooling though it's one I can live with.

Carl Wilson 410/01/2014 12:05:15
670 forum posts
53 photos

Castrol Ilocut 486. This is non soluble cutting oil. I have done quite a lot of work in stainless and I have found that this is excellent.

A 20 litre container can be had at fairly reasonable cost. My coolant sump is full of it. I bought the 20 litre container over two years ago and it is still 2/3 full.

For hand tapping etc I tend to use Rocol RTD. I would agree that dabbing on coolant is rather pointless. If you need it then it has to be flood.

As for WD40...Some time ago I was closing my workshop up whilst I went away for my job. I sprayed WD40 on my machine surfaces, rotary table etc to try to discourage corrosion (my old workshop was in an unheated outbuilding). On my return after 6 weeks, corrosion had occurred but only where the WD40 had been sitting. I now don't use WD40 either in my home workshop or at work. If I want a water dispersant I use GT40 which is silicon based.

Luke Graham10/01/2014 14:14:11
27 forum posts

My 2 pence.

I use flood suds, WD40, cutting oil from a brush or bottle, or nothing. That's on lathe and mill, with both carbide and HSS tools.

I've had the suds sitting around for ages now (a year maybe?) and it is fine, no smells at all.

Edited By Luke Graham on 10/01/2014 14:14:37

Carl Wilson 410/01/2014 18:12:15
670 forum posts
53 photos

I think a lot depends on whether we are talking about cooling or lubrication. A flood of coolant will obviously do both. Sometimes a small amount of lubricant, as can be provided by a brush or squeezy bottle application, can be very beneficial, and is what is required as opposed to a coolant. This afternoon I was parting an aluminium bar and used a quantity of Ilocut 486 in this way. It made a big difference.

Edited By Carl Wilson 4 on 10/01/2014 18:13:00

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