Any Recommendations for a Flood Coolant?

I bought the coolant system wth my Tormach 770. There is a sheet metal splash guard on either end of the table and an acrylic guard at the front. The column and the control panel at the back control splash in that direction. In addition, the tray has a guard on both sides and the back. I use a vinyl "shower curtain " held in place with magnets and that effectively controls and coolant splash as well aas chips even when using a facing mill. I wouldn't consider adding flood coolant to a lathe unless it was totally enclosed.

The coolant that I use is Premier Duracut from Tormach but I have seen good things said about Qualichem 251. I use flood coolant infrequently and have nit had a problem with it going rancid. Tramp oil is a problem. I manually skin the oil off the surface every so often. There are oil skimmers that will do that automatically. I have never had a problem with corrosion although I rinse the chips off the machine and wipe down the bare metal surfaces when done.

It is important to maintain the proper dilution. Too dilute and you will have corrosion problems. Too concentrated and you can strip paint off your machine. As coolant is used, water evaporates from the solution, increasing the concentration. The lost water must be replaced in order to maintain your proper concentration. For that, a Brix refractometer is essential. They needn't cost much. I bought mine on eBay for less than $20. The Brix scale is a measure of sugar concentration and is used in wine making. It does so by measuring the index of refraction of the solution. There is no definitive relationship between sugar water and coolant. If buying a Brix refractometer, you should buy one with the most sensitive scale. Mine is a 0 10 Brix.

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The refractometer should be calibrated by making up a few known concentrations of coolant solution and measuring the refractive index. With each new batch of coolant, I make up some standard solutions which I use for comparison. I make my solutions up by volume but they could just as easily be done by weight using a digital kitchen scale. Her ius a screen shot of the Excel spreadsheet that I use.
Coolant Dilution Schedule.JPG
I keep a sample of each of the dilutions in a small vial so I can check the refractometer from time to time.

If I were making up samples by weight, I would first make up one at the concentration that I intended to use by weighing a known volume of concentrate and diluting it to the desired volume and weighing it. From that, I would know the conversion from volume/volume dilution to weight/weight dilution.Then I would make up my standards to bracket my desired dilution.
 
For a home shop, I also vote for straight oil if you feel the need to pump something. No hazard of rust, no need to wipe up at the end of the day, and doesnt go rancid. A minor hit in cooling capacity and a bit more toward the smoke side of things.

I dab and squirt as needed, myself. A dental air/water sprayer off fleabay fitted to a pressure bottle makes the best cutting oil applicator known to man ;-)

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erikmannie said:
On my current lathe (which does not have a flood coolant system), I use dark thread cutting oil. It’s smokes a little, but I like that cutting fluid. Am I the only person that enjoys the smell of this?
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I have not had to mill or lathe anything that requires coolant, cutting oil has satisfied my every need--including the need to let it sit overnight without causing rust. In a hobby environment, one can use less tool face pressure and slower transits to cut efficiently without creating so much heat as to require cooling.
 
MrWhoopee said:
In a hobby shop, coolant is just too much trouble. Unless maintained properly and used frequently, it gets rancid and starts growing stuff. One of the things I don't miss about working in the trade is coming home stinking of rancid coolant.
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I would whole heartedly agree. One of my lathes , my horizontal bandsaw, and my power hacksaw are equipped for flood coolant. I DON'T USE IT ON ANY OF THEM. It had been used on the saws before I got them and made a horrible mess. A mix of old dried coolant and a swarf covered the coolant tanks, and the entire body's were sticky and nasty. Every time you bumped against either of them you got a permanent stain on your clothes.

I finally disassembled both of them and spent a week on each cleaning off the crud. I have been using the bandsaw for 20 years either dry or with a little stick lubricant as needed. I've been using the power hacksaw dry for over 5 years and probably will never go back to coolant.

The lathe has been in the shop about 5 years and I've always used brush on or spray from a bottle. I see no need to have coolant flying all over the shop, or getting rancid in the tanks.
 
I have not read all the comments yet but I had the same question a while back and someone on here suggested Mobilmet cutting fluid for use in you flood coolant tank. It is great for drilling, tapping and parting on the lathe. I've even used it for some turning. The good thing about it is you never have to worry about corrosion. I think I started w/2 gallons in the tank and now the level is to low to pump. It went on the floor, the stuff makes a mess. If I could fab up something to keep the oil on the lathe rather than the floor I will use it again for sure.
 
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This is all very interesting. I have been very happy with dark thread cutting oil. I am going to research if I can put that in my flood coolant system, but I wouldn’t want that spraying all over the shop, either!

EDIT: I see that this can be a fire hazard what with a hot chip falling into the oil.
 
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erikmannie said:
This is all very interesting. I have been very happy with dark thread cutting oil. I am going to research if I can put that in my flood coolant system, but I wouldn’t want that spraying all over the shop, either!
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Dark thread cutting oil has lots of sulfur and can't be used on aluminum.....
 
When I first got my lathe and set it up I fitted up a home made coolant system, and while it worked well I soon had the problem of the chuck spinning it everywhere. Wife was not happy when it sprayed all over her car. But a couple of months down the track, and it started going rancid. Drained it out and flushed the system, but this time it only took about 5 weeks to start going off. Discussed with a friend who runs a professional machine shop. His advice get rid of it, do not use unless you use it every day. He suggested using a hand spray bottle with a mix of lube oil and kero. Or just a small brush and a pot of oil, cutting oil if you must.

After some experiments I tried using Inox MX3 sort of a bit like RP7, WD40, which I already had in a squirt bottle I use it on everything, but a much better product. Many people have noticed that parts sprayed with WD40 will start to rust within a week. This will not happen with Inox or Lanox a sister product. Lanox is for very serious corrosion places, like near the sea, on boats, fishing gear, and very humid climates I live in a fairly dry climate, so rust is not a huge problem, but it still happens especially in winter where its cold and wet.

I have just returned home after being away for 8 weeks in the middle of winter. My lathe had no special preparation before I left, just the light coating of Inox form the last use. when I got home it was still clean and all the bright parts still shiny bright. Add some oil and away I went back to machining. BTW it's excellent for machining stainless steel and other difficult metals.
 
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