Maintaining the integrity of metalworking fluids is critical to the operation of machining systems. One company that produces digital handheld refractometers, which measure the composition of such fluids and thus their effectiveness, is Misco Refractometer. The Cleveland-based company manufactures two digital models specifically for metalworking fluids that are sold directly or through distributors.
The benefit of an accurate refractometer is obvious yet bears repeating. Every metalworking fluid is formulated to be effective within a concentration range. If the concentration is above this range, it means a machining system is using too much fluid and residue and other problems can emerge. If the concentration is too low, problems with corrosion, tool wear, and sump life may result.
“These fluids help maintain equipment worth millions of dollars,” says Kathy Widing, vice president of sales at Misco. It’s important for shop owners to invest in refractometers that accurately analyze the effectiveness of the fluids, considering the performance issues that are at stake, she adds.
The instrumentation Misco sells for metalworking fluids consists of the PA (for Palm Abbe) 201 and PA202X. The devices are reportedly more accurate than most competitive digital refractometers. They also eliminate errors caused by reading analog refractometers, which post data in scaled measurements. Widing credits the accuracy to the devices’ element-detecting arrays — 1,024 compared with 128 on most other digital refractometers.
The PA201 measures fluid concentration by the Brix scale, in a range of 0 to 56°. The PA202X can use two units of measure — Brix, in a range of 0 to 85°, and the 10440VP arbitrary scale, in the range of 0 to 30°.
The devices, powered by two AAA batteries with a life of 5,000 readings, are easy to operate. Each has a stainless steel sample well, sapphire prism, and evaporation cover that prevents evaporation and shuts out external light, which permits an accurate fluid reading.
A machine operator extracts 0.3 mL (two drops) of fluid in a pipette and places the sample on the sapphire prism. (The sapphire prevents scratching when fluid is wiped off after testing.) The evaporation cover is closed and the test button activated. Measuring takes 5 s. An internal light source is used for refraction and an automatic temperature compensation function maintains readings between 32 and 122 deg F (0 to 50 deg C).
The refractometers have 24-character backlit LCDs. The PA202X and another model, PA203X, can be custom programmed. The PA202X is programmable with either of the two scales, whereas the PA203 is programmable with five scales that include other fluid applications.
The devices are small and light. The PA202X, which weighs 249 g (8.75 oz), is 75 mm (2.9 in) at its widest point, 145 mm (5.7 in) high, and 2.95 mm (1.46 in) thick.
The PA models are manufactured in the U.S. Prices range from $325 to $525, with volume discounts available, Widing says.