Dumb Coolant Question

"Tim Wescott"

I only work on small stuff and as I make mainly prototype components there isn't a pressing need for screamingly fast cutting rates. I get away with spray-on cutting oils mostly. But cutting oils will keep things at a faily constant temperatute which can be an advantage on items made of aluminium which has a faily high coefficient of thermal expansion. By keeping it cool, your precision measurments will be more meaningful as thermal expansion wont play tricks on you as much. Its also an advantage when turning down a long rod supported with a centre in the tailstock because it wont grow longer with rising temperature causing you to keep adjusting the pressure on the tailstock handwheel.

Cutting oils seem to make the tool edges last longer too. However they ARE messy and I've never seen a satisfactory solution. You can cover the machine with splash guards which will always be in your way, or do without them and get covered in muck. Two things to watch for :- 1st, try not to get cooling oils on your skin for too long - they're not good for you. 2nd, watch out for the water diluted ones as far as rust goes. The water can separate and rust your machine between sliding surfaces where its very hard to get it all out.

Dean.

Tim, I've run machines for almost my entire life, starting at age 13, and spent years in commercial shops. I'd suggest to you that unless your machine is made for coolant, it would be difficult to use it successfully. Most industrial rated machines are built with coolant in mind, and usually have a built in coolant pump. If yours has, most of the problems have already been addressed. Even then, unless you have a totally enclosed machine, the modern CNC machines for example, running coolant is quite messy. Roughing steels and stainless, the coolant should be a full flow so you don't experience thermal shock. The idea is to keep not only the part cool, but the cutting instrument as well. With that in mind, when near the chuck it usually picks up a lion's share of coolant and whips it into the atmosphere as it is slung from the jaws and chuck body. You can easily build a sliding cover that goes over the chuck to catch that mess, but unless you can then direct the coolant back to the chip pan, you're pretty much screwed. That's where it's important to have a machine that was intended to have flood coolant.

Water based coolants are far nicer to work with, especially the chemical ones. I've had to use water soluble oil many times, and I can say with total honesty I hate it. If you use chemical coolants, when the day's work is done, you can use the coolant itself to wash down the machine, which it usually needs. The heated headstock has a tendency to evaporate a lot of water, leaving the chemical deposit behind. By washing it down with coolant, then blowing off the machine, you generally don't have any issues with rusting as has been suggested. The one negative is that many of them eat paint, so your headstock and areas where there's considerable concentration of coolant tend to get stripped down to the iron over the long haul.

One of the problems of running coolant is the anaerobic bacteria that thrives in it. Tramp oil is a large contributor to the problem, so if you can skim the coolant and aerate it, it will have a considerably longer life span. The biggest problem with using coolant on a hobby basis is the infrequent use. You can use a small aquarium pump and stone to supply air to the coolant, which helps considerably. The other option is to run the coolant for several minutes every day to keep it circulated and aerated. That does wonders for keeping the smell down.

Good luck!

Harold

Misters work fairly well, but they have severe limitations. If you're roughing steels, a mister would be pretty useless. First problem is the device getting in the way, the other could be thermal fracturing of your cutting tool. Misters work very well on a mill, especially running HSS cutters, where you can keep the stream on the cutting tool, but that's not quite as easy on a lathe. Unless you're breaking the chips well, they tend to get intertwined with the cooling device. Their usefulness falls off when you need them most, running carbide, where severe heat is generated. There's nothing quite like flood cooling.

Harold

I use WD-40 for small jobs... I buy the stuff to put into a spray bottel... It work quite well...

You can make or buy a curved acrylic shield that goes over the chuck area and is hinged so it can be lifted out of the way. It keeps the coolant from getting slung all over.