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Thread Grinder Produces Workpieces More Than 6 Feet Long

Automatic phase, notch-position and effective-diameter adjusters along with automatic wheel in-feed position adjustment ensure Mitsui Seiki’s GSH 200A thread grinder delivers consistently repeatable precision.

Posted: April 7, 2021

Mitsui Seiki’s GSH 200A thread grinder produces workpieces more than 6 feet long and almost 8 inches diameter. Automatic phase, notch-position and effective-diameter adjusters as well as automatic wheel in-feed position adjustment ensure accuracy.

Engineered to grind screws up to 78.7 inches (2,000 mm) long and 7.9 inches (200 mm) in diameter, the GSH 200A thread grinding machine from Mitsui Seiki USA Inc. (Franklin Lakes, NJ) delivers high processing speeds and consistent precision on a wide variety of applications.

Maximum diameter swing over the table is 18.9 inches (480 mm) and distance between centers is 88.6 inches (2,250 mm). Capabilities include 15 kW direct-drive motor that produces maximum wheel spindle speed of 6,000 m/min. X-axis stroke of 330 mm features a rapid feed rate of 5m/min. Z-axis stroke is 2,150mm with 10 m/min rapid feed. Maximum spindle speed: 200 rpm.

Sliding machine surfaces are hand-scraped to maximize precision. In addition, multiple systems minimize thermal displacement that can affect thread accuracy and consistency. Lubricant in the table feed lead screw and shaft core stabilizes the components’ temperatures. A main coolant nozzle cools, lubricates, and removes sludge at the grinding point, while separate work area and bed coolant showers equalize internal machine temperatures. Oil and air lubricate and cool grinding-wheel axis bearings (machine is compatible with both oil-based and water-soluble coolant, selectable when the machine is produced).

Operators can use CBN as well as standard grinding wheels, facilitating grinding of hardened steels as well as unhardened workpieces. CBN can grind more than two times faster than standard wheels while providing longer life, which extends dressing interval and reduces dressing time per workpiece. Mass- production scenarios multiply those benefits. Maximum diameter for standard wheels is 18.1 inches (460 mm) and peripheral speed is 60 m/sec; maximum CBN wheel diameter is 15 inches (380 mm) and peripheral speed 120 m/sec.

The machine’s 3-axis NC dresser employs two linear axes (U,W) and one rotary axis (B) to produce highly accurate profiles in both CBN and standard wheels. Disc-type rotary diamond dresser provides significantly longer life than single-point diamond.

Automation features including phase adjuster, notch-position adjuster and effective-diameter adjuster permit operator to leave the machine during operation instead of staying put to adjust the steady rest and oblique diameter. Effective- diameter adjuster uses a touch probe to contact the thread groove and measure change in diameter by scanning. Acoustic emissions (AE) sensor built into the wheel spindle provides automatic wheel in-feed position adjustment.

Optional heavy grinding wheel replacement support mechanism facilitates safe and easy changeovers.

Control: Fanuc 31i-B control with 14.7-inch (375 mm) touch panel LCD operator can move to wherever it’s most convenient.

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