Refractometers - What Range to Order

[bill south]

I have a benchtop (<3000rpm) cnc mill and use Travers Tools WS5050 water soluable oil as a flood coolant. I'm constantly having to add water since the machine sits for fairly long periods of time and the water (?) evaporates. The recommended mix of the coolant is 10:1 to 35:1. My initial mix was about 20:1 but I've had to add water several times. My indicator of low liquid level, is poor performance of the pump (oops, not too scientific!!!!).
To obtain a better mix of coolant, I want to purchase a refractometer but at least 3 different ranges are offered. 0 - 10%, 0 - 18% and 0 - 36% on the Brix scale.
My question is, for home use and with the above mentioned coolant, what is the optimal range I should order? I want to purchase the lowest range necessary which will result in maximum scale sensitivity. I'm looking at the units from mcmaster carr and also noted that they are supplied as temperature compensated and non-temperature compensated for about the same price.
Can someone point me in the right direction? Is there a better or cheaper way to test the coolant for a proper mixture? The cost of the instrument is $90 - $110. Not real bad and I do want to make sure my coolant is mixed to the proper levels.
Sorry for the novice questions, but I can't seem to find an answer in the archives.
Bill

[dpuch]

You will have to find out from the coolant manufacturer or possibly paperwork that came with your coolant. They should be able to provide you with the Brix scale values (not percent) for a given mix %. The refraction will differ for different coolants at the same mix %

[Sideman]

Can I follow up Bill's rookie question with another rookie question? I already have an automotive refractometer that measures coolant and battery acid levels. Is there a conversion table that would allow me to use what I've got? The coolant I'm using is Hangsterfers 500.

Yet another rookie question: What's the best way to clean up the mill? I've been using a paint brush, rags, and the blower side of the shop vac. Air or use a hose to direct the coolant? The mill is in my basement so I'm trying hard to keep the chips contained.

Thanks in advance,

Rick

[Chuck Reamer]

I use a Zebra 0-32 and have no acuracy problems with it and am very pleased with the product. Remember most coolants have a refractometer factor, for the coolant I use its 2.7. So my refrac reading has to be multiplied by 2.7 to get my final percentage. I have never heard of the temperture comp so I cant help you there.

Sideman, are you running a manual machine or an enclosed CNC (must be little if its in your basement)? With an open machine it is very hard to keep the area clean.

[timlkallam]

I use the same coolant in my cncs rustlick 5050 .Get a 0-32 scale you will still be able to clearly see the numbers.

[eject_21]

Whichever meter you use make sure you calibrate it. Mix up a small batch to the percentage you want,then check it on the refractometer. We use a few different types of coolant in our shop and only have one refractometer. We have a chart to check it against. Different coolant types will measure differently when mixed to the same percentage of water. Or you can just do what I do, When it gets in your eyes, it should burn for at least 6 seconds, but not longer than 14 seconds.Adjust as needed.

[bill south]

Thanks Guys for all the input.
As I mentioned in post 1, I use 5050 also and it finally dawned on me to download a spec sheet with all the answers.
Based on the info provided, I also bought a 0 - 32 range instrument which works fine. However, in the instructions, they recommend to perform the tests which eject_21 recommended.
Actually mix known amounts of coolant with a measuring cup (as recommended for the brand of coolant), measure them with the refractometer and record the reading. It really doesn't matter what the numbers are (scale???) as long as the instrument is calibrated and is on scale. Of course, the finer the scale the more sensitive the reading. But, for my home use, ball park works. BTW, my mixture was 100% to stong. Had to dilute the heck out of it.
As for cleaning, I just use a brush, wd 40 and reoil the ways.
Have a good day.
Bill

[NinerSevenTango]

A couple more pointers for anyone who reads this ....

There is a vendor on Ebay who sells refractometers for around $60, they work fine.

There isn't as much difference between refractometers with different ranges as you might expect. Say, between a 10% one and an 18% one, or whatever. As long as the range is adequate for what you want to measure. What happens is, the one with the smaller scale just reads with a fuzzier line.

Calibration -- just take some room temperature distilled water as a sample, and zero the reading.

The scales can be printed on the reticle for all kinds of different mixes -- Brix just means the scale is for measuring percentage of sugar in water. You can easily determine the multiplying factor by mixing a known ratio and measuring it, as mentioned above. So if you have a battery acid one, it should work fine if you can see a reading with the solution you want to measure.

Just be aware that contamination with stuff that has a different refractive index will cause some error. For machining work it probably isn't that touchy, though.

If you want the cheap refractometers to last, don't rinse them under running water, just wipe them off. Once the inside gets wet, it's not as much fun to use any more. For daily or heavy use, consider an electronic one -- I found a web store that had one for around half the price of the ones offered on ebay. That one is sealed so you can rinse it under a faucet.

--97T--