I have a pair of ex-industrial Bijur Spraymist systems. One on the lathe and one on the mill. Very effective but a touch tricky to set just so. The mill one in particular as the main unit is on the main column a couple of feet lower than the nozzle so things tend to drain back, despite having a check valve, so start-up can be iffy unless the volume valve is opened until flow established. Which is a pain. The one on the lathe is mounted above the nozzle at the back of the machine and does not suffer so but has to be lifted down to refill.

Its important to direct the flow accurately onto the workpiece so that the minimum amount of coolant is used. Its easy to create an evil fug by using too much flow. With the Bijur system a certain amount of fiddling with flow volume and air pressure allows a well controlled spray to be directed at the cut so virtually all the coolant condenses onto the work throwing very little into the air. Still gets everywhere on the working area of the machine tho'.

Having the mist systems lets me use coolant all the time except when working dry is best which helps enormously in getting good finish as well as extending tool life. You do get overconfident tho' and tend to exploit industrial level speeds and feeds. If the system glitches things go wrong fast!

Despite having pumps and sumps I only used normal free flowing liquid systems when unavoidable due to the splashy mess and long clean up times. An adjustable nozzle hand squirt bottle was better than nothing but still pretty messy and not that effective.

Despite their effectiveness I'm unsure as to whether mist systems are really worth the effort in a Model Engineers workshop where its rarely necessary to move lots of material fast. The systems are relatively expensive and a reliable supply of compressed air essential.

Clive

When it comes to small, quiet, compressors best to look at the tank mounted dentist / lab / industrial type such as Bambi or Jun-Air. I've used both and can confirm the low noise level. Not cheap new but turn up fairly often on E-Bay at acceptable prices. There are other makes too. Being intended for continous running they are durable so generally safe to buy used. Bambi have a decent spares policy. Twin or triple "cylinder" versions of the diapharm compessors intended for airbrush and similar use will probably handle the air requirements but generally are priced to meet the market so are less durable. Often not happy at continous running. The baby vertical 40 psi rated Burgess / Hydrovane intended for spray gun duties is another possibility. But getting rare now and no tank either.

Given appropriately diluted coolant, say 2 or 3 %, mist systems provide a fair degree of cooling due to evaporation of the water content. Change of state from liquid to vapour absorbs a fair bit of energy right at the cutting point. The air blast contributes too. The neat oil film left behind is effective at controlling buit up edge tendencies.

Air blast is great when milling as it clears chips preventing double cutting which not only ruins finish but also hits tooling life. been known to just use neat air for this reason when the work piece is going to be a PIA to clean.

Clive

If you look at the HSE website on the perils of machining, the health effects of cutting fluids are one of their greatest worries, certainly it seems to cause very many health problems. Spraying a mist of coolant suggests to me that at the very least the choice of a safe fluid must be important.

http://www.hse.gov.uk/pubns/indg365.pdf

Best advice in that guide – don't put oily rags in your pockets…

Neil

Hmmm, may have to rethink the mist system & just use hand spray / air blast methodology…

George

Some of you on here will know of my obsession s about coolant (metal working fluids). No mention gets ignored by me.

Has anyone tried through tool coolant?

Jerry

I have a Koolmist spraying water only, for cooling woodworking tools whilst grinding. Surprisingly cold and very little loose water – leaves tools damp rather than sopping. Lots more water gives little cooling advantage. The official additive for machining appears only to be on sale in the USA. Water miscible oil should not be used for health reasons.

I did not buy a tank, but use a mains water filter case, which could be easily rigged to give pressured fluid delivery. Paint spraying with a pressure pot gives good control of droplet size; going in the "wrong" direction for paint (larger droplets) is quite possible, so I don't see why adjustment of fluid pressure and air should not do the same for the Koolmist – but I've not tried it!

I have a Bijur system, a lot of Bridgeport milling machines were fitted with these. The fluid container is pressurised, I think the makers recommend about 10-15 PSI, air and fluid feed to the nozzle through separate tubes at the same pressure, the idea is that relatively large droplets of fluid are carried by the air leaving the nozzle. There should not be any fog but if you really need one, cranking the air pressure up to max should do it!

One of the last things I almost got involved in before retirement, was the use of compressed air as a coolant, just an accurate blast of air. Most (90%) of the material was Al. Alloy usually 6061 T6, 2024 T3, 7075 T6. Air cooling probably wouldn't work on steel alloys. The theoretical advantages were several, no mess, clean swarf ready for compacting (normally the compacted swarf contained a fair amount of coolant which had to be filtered and cleaned prior to reuse) supposedly better cutting, as long as the tools were sharp.

Any thoughts??

cheers

Bill

Here's an example of an MQL system. They claim the actual qty of lubricant used is minimal ("typical applications use only 1oz. of lubricant per 8-hour shift&quot and this accords with Mr Saunders across at NYC CNC, who made a short video about his experiences using the Trico system.

The downside of this particular system is the cost (over £400) but it can operate down to 60psi / 4 bar and requires about 1.7cfm per nozzle.

Murray

My only experience of spray mist was coughing profusely and sore eyes from the fog. Will not go there again, I much prefer WD40.

Had to use spray mist when gun drilling – the air and coolant went through the drill bit – the finish, size and direction were in the 0.0001" tolerance, wonderful tools. Still had me coughing and eyes smarting though especially if the coolant hadn't been thoroughly flushed before use (old spray mist stank of mouldy fabric).

Always cut dry now in the garage and squirt some WD40 when needing a finish or parting off.

Trevor

Edited By Trevor Wright on 10/02/2015 13:08:29

I worked in a factory where spray mist coolant was used on several horizontal borers, I wouldn't have it on my machine where I stuck to flood coolant. One afternoon I walked out, the "fog" was so bad, I had irritation in my throat and upper chest. I returned the following day with a formal complaint addressed to the MD. I will give him his due he spent £10K on installing roof extractor fans, trouble was it passed through our lungs before it got to the fans!!!

Modern coolants are expected to perform a whole host of functions other than just cooling the cutting tool and the job. To this end you will find biocides, rust inhibitors etc, all of which end up being breathed in by the operator in varying degrees dependant on the accuracy of the coolant dilution rate used!! To this end we installed a premixer on the neat coolant barrel, this was checked monthly by the coolant suppliers rep. We still had one clown who thought he knew better and would enrich the mixture claiming it would not harm us.!!!!!!!!!!!

HSE take many knocks these day but on the issue of spray mist coolant listen to what they have to say also google spray mist coolant problems and see what horror stories you find. Don't wear your ear defenders you are deaf, don't wear eye protection you are blind, damage you lungs and you will end up with a nice fitting box!!

regards David