Choosing a Grinding Coolant

A discussion of the pros and cons of various coolants (or lubricants) used in cutter grinding for woodworking equipment. July 23, 2014

Are there pro's and con's to soluble oil and water-based coolant grinding HSS profiles or is it just a personal preference type of thing? I received a flyer in the mail today from Grindclean Lubricants and was just wondering if a soluble oil was any better than the water based coolant I currently use from Weinig.

Forum Responses
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
For manual profile grinders I use and recommend water based coolants. I have used several over the years and found some that perform well and have not caused any breathing or skin issues. On the other hand, I have used some that remove paint and cause skin rash and breathing problems. The first thing to remember is to mix the coolant to the correct ratio. Too rich of coolant can cause health issues while too lean of coolant can increase the risk of rust on the tools and machine. I have also seen the same brand of coolant change its formulation and sell the product under the same name. I suggest that you use a good coolant dealer that will stand behind the product and maybe one that uses the product on a day to day basis.

From contributor U:
I have used water based coolants my whole career. I currently use the Grindclean coolant and it works as good as the Weinig Too cool but is better than the Weinig Rondo coolant. The Weinig Two cool and the Grindclean both have additives that prevent leaching of cobalt from grinding carbide (turns the water red). The Weinig Rondo cool does not have this additive to prevent leaching of cobalt. So in short, all good products just make sure you get the coolant that best serves your needs. Oh the Grindclean also has a smell of bubblegum added, although this is not important to me it does add a better smell to the room other than ordinary coolant smell.

From contributor D:
Oil! Well kind of anyway. Iím a knife grinder by profession, and have tried just about every fluid out there. Iím extremely sensitive to most petroleum based fluids, they make me feel like Iím covered in gasoline and give me a spacey feel in my head at the end of a long day. I found a soluble oil fluid that is made from corn oil, made by Renewable Lubricants and I love it. Performance wise I would just rate it average. It is absolutely fantastic for controlling rust though, better than any water based fluid Iíve tried. On the negative side it is opaque though (like milk), and kind of makes it a pain to see what youíre doing. Also, it makes a mess in your machine with tramp oil. It needs to be changed more often in hot weather (it starts to stink). I agree I donít think there is a right answer to this question as many factors figure into a decision. Hard or soft water, sensitivities, how much carbide you grind, how often you clean your machine, etc. Keep trying different brands until you find one that fits you.