Coolant Concentration

[syscore]

I found some old references to this issue, but I thought I would throw it out here for newbies (I just came across it myself). When measuring coolant concentration using a refractometer, make sure to multiply the reading from the refractometer by the refractive index of the coolant. I have been happy with Tormach's Durakut, but it has a refractive index of 2.8, so when I mixed it to get the refractometer reading to 5%, I was actually at 2.8 * 5% = 14%. No harm I guess, but I used 3 times as much concentrate than I needed. I don't know why Tormach doesn't make more of a mention (or any mention) of this in their documentation. Not even in the documentation for the refractometer they sell, which is identical to the one I got on Amazon for $15. When I mixed it by hand, I was pretty close to 2% (according to the Refractometer), which is actually the right value. 2.8 * 2% = 5.6%.

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[m1n1m]

Haas automation has a video series on YouTube about coolant. Just search haas coolant and you will find them. They mention this in the tools of coolant video and there are a lot of good maintenance tips there. Worth watching

[sharmstr]

Heads up. That Duracut is going to rust everything it touches. I cant believe Tormach sells it.

[GLCarlson]

I found some old references to this issue, but I thought I would throw it out here for newbies (I just came across it myself). When measuring coolant concentration using a refractometer, make sure to multiply the reading from the refractometer by the refractive index of the coolant. I have been happy with Tormach's Durakut, but it has a refractive index of 2.8, so when I mixed it to get the refractometer reading to 5%, I was actually at 2.8 * 5% = 14%. No harm I guess, but I used 3 times as much concentrate than I needed. I don't know why Tormach doesn't make more of a mention (or any mention) of this in their documentation. Not even in the documentation for the refractometer they sell, which is identical to the one I got on Amazon for $15. When I mixed it by hand, I was pretty close to 2% (according to the Refractometer), which is actually the right value. 2.8 * 2% = 5.6%.

Always something to learn...(this was a new one to me, too).

However. Falcon says that Duracut 525 has an RI of around 1, and the Tormach stuff is apparently similar. IF that's right (I dunno, and don't use Duracut anyway) then using an RI of 2.8 will get a seriously understrength system. And those usually cause trouble- rusting if nothing else. Just on general principles, an RI of 2.8 for a solution of an organic in water seems high.

Not correcting for RI will lead to overuse of concentrate, if the RI is >1. Cost aside, that's likely to result in a more robust coolant - that is, one less prone to fail due to too little preservative or rust inhibitor. A shop using barrels of coolant a month may need to worry; those of us who use a pail every year or so might look on that as cheap insurance.

[syscore]

Always something to learn...(this was a new one to me, too).

However. Falcon says that Duracut 525 has an RI of around 1, and the Tormach stuff is apparently similar. IF that's right (I dunno, and don't use Duracut anyway) then using an RI of 2.8 will get a seriously understrength system. And those usually cause trouble- rusting if nothing else. Just on general principles, an RI of 2.8 for a solution of an organic in water seems high.

Not correcting for RI will lead to overuse of concentrate, if the RI is >1. Cost aside, that's likely to result in a more robust coolant - that is, one less prone to fail due to too little preservative or rust inhibitor. A shop using barrels of coolant a month may need to worry; those of us who use a pail every year or so might look on that as cheap insurance.

Tormach used to have the RI = 1.0, but then updated it to 2.8 after a user here contacted them. Here is a thread about it ...

https://www.cnczone.com/forums/archi.../t-262920.html

I have been using Durakut for a year now, using the 20 : 1 mix ratio, and haven't had any issues. I only yesterday thought about checking the concentration with the refractometer that had been sitting in my drawer all this time, and saw that it said 2%. After adding and adding and adding, I thought about looking up the issue and came across the above thread. I think I am going to drain a gallon into a gallon jug and add water to thin it out some. Right now it is close to 14%.

[GLCarlson]

Tormach used to have the RI = 1.0, but then updated it to 2.8 after a user here contacted them. Here is a thread about it ...

https://www.cnczone.com/forums/archi.../t-262920.html

I have been using Durakut for a year now, using the 20 : 1 mix ratio, and haven't had any issues. I only yesterday thought about checking the concentration with the refractometer that had been sitting in my drawer all this time, and saw that it said 2%. After adding and adding and adding, I thought about looking up the issue and came across the above thread. I think I am going to drain a gallon into a gallon jug and add water to thin it out some. Right now it is close to 14%.

Thanks. That's certainly what someone said, in the thread, quoting Tormach. And Tormach does indeed claim that on their website.

There is no RI information on the Durakut 4010 MSDS. They do list some components, mostly TEA and an ethylene oxide/propylene oxide polymer. None of those materials has an RI as a pure substance above 1.5 or so. A mixture that's 70% water isn't going to be higher than the pure substance itself.

Further, that kind of RI just doesn't happen with aqueous liquids. Never mind what amount to fairly dilute water solutions. Pure glycerin is around 1.474; 85% sugar/water is 1.5; methylene iodide is 1.73 or so, and offhand I can't think of any liquid, let alone an aqueous solution, that goes over 2. Heck, the RI of diamond is only about 2.4! Standard RI test solutions for lab calibrations run from around 1-ish to around 1.6 or so.

For what it's worth, I think Tormach is stating an impossibility. If that's leading to a very high correction and a corresponding low concentration of coolant, I'd expect the coolant rust inhibitor to be way under spec and likely to fail.

I'll go poke Tormach on this one. Maybe I'm missing something obvious.

Edit: Found the Durakut 4010 product data sheet. RI claimed to be 1.0 by the manufacturer. Based on the published chemistry, I'd bet it's a bit higher than that. 1.028, maybe? See first result (shows as 525, but downloads 4010 page):
Durakut 4010 refractive index - Dogpile Web Search

[Steve Seebold]

I have been using Swisslube Blazocut 2000 Universal got about the last 25 years.

I used on a Mazak when I worked for someone and I have used it on my own machines since 2001 and I have never had any rust issues on any machines.

I’ll run it at 6% when cutting aluminum and up it to 10% for cutting steel or any exotic material like 6-4 titanium or 718 Inconel.

I use the same mixtures on my Tormach PCNC 1100. I’ve been using the Blazers since my machine was new in July 2011 and again, I have had absolutely “NO” rust issues.

[m1n1m]

Check the Bcool 755 from Blazer. It’s a newer coolant and according to the Blaser sales rep it keeps the machine cleaner and it outperforms the blasocut on most things. I haven’t tried 2000 tho and I have very little experience with bcool755 yet but it’s worth looking into I think.

[syscore]

Yep, that's what my data sheet says also. However, I do think it is 2.8 as Tormach now suggests. If you make up a 20:1 mixture according to the label the concentration should be 4% to 6%.

I think the issue is that 2.8 is not the "refractive index" of the coolant, it is the multiplying (brix) factor required to convert the reading given by the refractometer to an actual percentage. And these factors can go as high a 3.3 for synthetics ...

https://pdocs.masterchemical.com/mcc...erminology.pdf

Unfortunately, this factor has been confused with actual refractive index.

The best way too determine this factor is as RDSI did, mix a small batch with perfect proportions and then see what that gives you, on the refractometer. In the case of Durakut, the number works out to be 2.8.

Note: The "brix factor" is also called the "refractive index FACTOR". Huge misunderstanding when we lose "factor".