The Basics Of Coolant and Cutting Lubrications

Coolant and proper lubrication while machining is critical when being a successful machinist But they can get a little tricky. Dealing with coolants can be a challenge and that’s not just because you are handling huge vats of liquid. Like everything else in the world of machining, there are 1 million different scenarios and methods to consider when choosing your cutting lubrication. You may notice that I am mentioning lubrication and coolant together. Coolant is the term most often used but the used of the substance does multiple tasks which include cooling your tools, lubricating the cutting process, and clearing chips. While you are cutting and how you’re cutting will determine how you use coolant, and the method of delivery.

Flood coolant literally floods and sometimes blasts your part with this liquid. This assist with getting chips out of the way while also lubricating and cooling your tool. Depending on what you’re cutting the mass is typically worth it. Miss coolant is another option, it uses a combination of air and coolant to deliver a saturated mist at your cutter. This helps clear chips and lubricate but it doesn’t do much cooling. And then there is boring old air, no lubrication, and only a little cooling but it does sufficiently clear chips. When deciding on which cooling settings to use this depends on two defining factors which are your cutting tool and the material you’re cutting.

For the sake of simplicity and to keep this passage under 10 pages long we will just focus in on high-speed steel versus carbide cutters. Carbide tools can get much hotter than high-speed steel and therefore are more susceptible to thermal shocking. Meaning different parts of the cutter expand by different amounts causing the cutter to chip, break, or even explode. This means that you typically want to go light on coolant while using carbide tools. You may need to use miss coolant for any type of  milling machine coolant (combination of air & coolant). High-speed steel is more flexible so no explosions, but it will still get hot, so flood coolant is recommended. Without coolant on high-speed steel you run the risk of extremely faster wear or even the tool welding itself to your part. The material you’re cutting will change how you use your coolant as well.

Aluminum is known to be a forgiving material because it’s a soft metal but that makes it a little gummy so you’re better off using flood coolant on milling machines that drill with aluminum. Miss coolant will work but the deeper your cuts the more chips you will accumulate. On the other hand, steel is a much harder material which generates more heat while cutting. While steel is less gummy then aluminum the chips can still build up. With the hot cutter and mounting chips, it’s best to keep clear of your tool with an air blast technique. Now stainless steel is harder yet but still has some of the gummy features of aluminum so flood coolant with high lubricity is ideal.