EVALUATION OF METALWORKING COOLANTS USING THE MICROTAP TAPPING TORQUE TESTER

For decades, the Falex Pin and V-Block machine was the primary laboratory method for evaluating lubricating properties of metalworking coolants. This test apparatus is a friction producing device that provided load and torque data, but does not replicate the metal cutting (chip formation) operations occurring at customer’s facilities. It was also limited to evaluations on steel.

Over the years, other bench top lubricity analyzers were developed that more closely duplicated machining operations. One of these is the Microtap Tapping Torque tester, an industrial tapping machine modified for lab testing of coolants on various types of metallurgy. Standard metals include 1018 Steel, 6061T6 Aluminum, and 316 Stainless Steel.

The MicroTap Tapping Torque tester uses a standard HSS tap to machine threads into predrilled holes in a 2 inch x 14 inch test bar. The force or torque required to tap the hole is measured as coolants is applied to the tap and metal test bar.

Test results are reported as either a torque value in Ncm (Newton centimeters) or as percent efficiency. The % Efficiency is the ratio of the torque value of a control coolant to the torque value of the test coolant. The control coolant is typically assigned an efficiency of 100% and test coolants will fall above or below this number. Metalworking fluids with lower torque values and higher efficiencies have better lubricating properties. Coolants with efficiencies within 5% of each other have comparable lubrication characteristics.

The MicroTap machine has been used to compare lubricity properties of the new Chemetall metalworking coolants as well as numerous competitor’s products.

Product	Conc %	Torque 1018 Steel	% Efficiency	Torque 6061 T6 Alum	% Efficiency	Torque 316 SS	% Efficiency
		Ncm					Ncm
Synthetics
Gardocool C 9116	5	194	120.1	238	105	88	98.9
Castrol Syntilo 9954	5	179	130.2	251	99.6	88	98.9
Houghton Hocut 767	5	267	87.3	307	81.4	87	100
Neo-Synthetics
Gardocool C 9156	5	264	88.3	258	97	86	101.2
Semi-Synthetics
Gardocool C 9127	5	266	87.6	248	100.8	88	98.9
Gardocool C 9157	5	233	100	250	100	87	100
Gardocool C 9158	5	254	91.7	241	103.7	88	98.9
Soluble Oils
Gardocool C 9179	5	169	137.9	141	177.3	82	106.1
Master Trim E 206	5	238	97.9	196	127.6	79	110.1
Blasocut BC40NF	5	284	82	194	128.9	111	78.4