Coolant strength

[depronman]

I use a semi synthetic coolant on one machine and a fully synthetic coolant on another machine (may well standardise on the fully synthetic in the future)
I need to check oil concentrate in the coolant so thinking to buy a refractometer
Are the ones on eBay at around £10 as used for alcohol or salt content for aquariums suitable for checking coolant ?
Just don’t want to buy something that is not suitable

Cheers. Paul


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[Muzzer]

I've got one at home so could check this weekend when I'm back if you don't get an answer before then.

I'm not sure what the refractive index needs to be and how that compares with beer etc. Hopefully the instructions / spec sheet will give a clue.

[depronman]

I did some research and you need a brick scale of 0 to 10
Got one from Amazon and it arrived today
Works a treat

Cheers. Paul


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[Muzzer]

Mine's from Index Instruments in Cambridge. http://www.indexinstruments.com/media/1115/visual_refractometer_leaflet.pdf

The label says REF-102C, which seems to be a "cutting oil" version of the REF-102. The label on the box says "0-18% cutting oil" and the website seems to suggest that's possibly also 0-18 Brix, although they don't actually recognise the REF-102C as such. RS sell a version which talks of "0-18 Brix" and also "0-18% cutting fluid". Remarkable coincidence?

Bottom line is that Brix and % cutting fluid are being used interchangeably. There's no obvious explanation why that might be, given that Brix is generally used for alcohol. We may never know!

[depronman]

I’m in contact with the coolant supplier to establish the brix multiplier for there semi and fully synthetic coolants that I use
For now I’ve mixed up a control batch at 5% and measured this on the refractometer and got a brix reading for it. When checking the coolant in the mill which felt a bit thick it was some three times the brix reading on the control sample
Water with a small amount of concentrate was added until I got to the same brix reading
It now feels right so all good until I get the official data from the coolant supplier

Thanks for you input from another Cnc’er in st Anne’s
Cheers paul


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[JAZZCNC]

Synthetic coolant is a completely different animal to the typical emulsion and soluble oil type coolants that typically have a 1:1 Brix (Ri) factor where semi and fully synthetics coolant can have up to 3.5 factors.

The Refractometer range (RR) doesn't actually have to be too large for synthetics coolants because of the high Brix Factor, that's why a 0-10% range is more than enough.

For instance, if the coolant Brix multiplier factor is 3.3 and you want a coolant concentration of say 8% which is a typical concentration then the RR would only need to read 2.5 so even a 0-5% refract would be plenty wide enough.

[Colin Barron]

I’m in contact with the coolant supplier to establish the brix multiplier for there semi and fully synthetic coolants that I use
For now I’ve mixed up a control batch at 5% and measured this on the refractometer and got a brix reading for it. When checking the coolant in the mill which felt a bit thick it was some three times the brix reading on the control sample
Water with a small amount of concentrate was added until I got to the same brix reading
It now feels right so all good until I get the official data from the coolant supplier

Thanks for you input from another Cnc’er in st Anne’s
Cheers paul


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An easy solution (sorry) is to make a graph using control batches of different percentage concentrations and then in future you can compare refractometer reading to concentration.

[Muzzer]

Thanks, Dean, that makes a lot of sense. I'm actually using Castrol Hysol XF. When I look at the datasheet, there's an entry called "refractometer factor" that I hadn't noticed before. For this stuff, the factor is 1.1, so hardly worth bothering adjusting for.

In my case, I'm forever having to top it up with water to make up for evaporative losses - I guess that's the price you pay for a heated workshop. I just top it up to the level and periodically check the concentration.
https://www.thelubricationstore.com/wp-content/uploads/castrol/datasheets/CastrolHysolXFDataSheet.pdf

[JAZZCNC]

In my case, I'm forever having to top it up with water to make up for evaporative losses -

Tell me about it, you should see the losses we get on our Hurco VMC. Between hot parts and a high-pressure coolant system, we are forever topping up the coolant, it's surprising how much you can lose just on the parts, even after blowing them off with air.!

But our biggest challenge and pain in the arse is contamination from the way-lube oil which is pumped to the linear bearings and ball-screws. It's a nightmare because while I can control the time the pump is on through the controls PLC I can't have it off for too long for the risk of killing the linear bearings so we get a film of oil on top of the coolant.

I'm trying to come up with a simple oil skimmer, so any ideas will be greatly appreciated.?

[Colin Barron]

Tell me about it, you should see the losses we get on our Hurco VMC. Between hot parts and a high-pressure coolant system, we are forever topping up the coolant, it's surprising how much you can lose just on the parts, even after blowing them off with air.!

But our biggest challenge and pain in the arse is contamination from the way-lube oil which is pumped to the linear bearings and ball-screws. It's a nightmare because while I can control the time the pump is on through the controls PLC I can't have it off for too long for the risk of killing the linear bearings so we get a film of oil on top of the coolant.

I'm trying to come up with a simple oil skimmer, so any ideas will be greatly appreciated.?

Jones and Shipman made filters for their grinding machines, could one be adapted? If you do have problems with coolant getting into linear bearings etc it may be worth doing rust checks using standard steel chips, filters and a petri dish. By checking the number of rust spots left on the filter it gives you a rule of thumb on coolant condition.