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Mitsui Seiki’s GSH 200A Thread Grinding Machine combines flexibility of application, high processing speeds, and consistent precision to complete an extensive selection of threading jobs. The GSH 200A is engineered to handle a wide variety of workpiece sizes. Maximum diameter swing over the machine table is 480mm and distance between centers is 2250mm, enabling the machine to grind a maximum screw length of 2000mm and maximum workpiece diameter of 200mm.
The machine’s capabilities include a 15 kW direct-drive motor that produces maximum wheel spindle speed of 6000 m/min. X-axis stroke of 330mm features a rapid feed rate of 5m/min, Z-axis stroke is 2150mm with 10m/min rapid feed, and maximum work spindle speed is 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 temperatures of those components. 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. The GSH 200A machine is compatible with both oil-based and water-soluble coolant, selectable when the machine is produced.
The GSH 200A permits users to apply CBN as well as standard grinding wheels, facilitating grinding of hardened steels as well as unhardened workpieces. CBN can grind more than 2 times faster than standard wheels while providing longer grinding life, which extends the dressing interval and reduces dressing time per workpiece. Mass production scenarios multiply those benefits. Maximum diameter for standard wheels is 460mm and peripheral speed is 60 m/sec while maximum CBN wheel diameter is 380mm and peripheral speed 120 m/sec.
The machine’s 3-axis NC dresser employs 2 linear axes (U,W) and 1 rotary axis (B) to produce highly accurate profiles in both CBN and standard wheels. A disc-type rotary diamond dresser provides significantly longer dresser life than single point diamond.
Automation features on the GSH 200A include an automatic phase adjuster, automatic notch position adjuster and automatic effective diameter adjuster. Together, the features permit an operator to leave the machine rather than remaining there to adjust the steady rest and oblique diameter during the operation. The auto effective diameter adjuster uses a touch probe to contact the thread groove and measure change in diameter by scanning. An acoustic emissions (AE) sensor built into the wheel spindle provides automatic wheel in-feed position adjustment.
An optional heavy grinding wheel replacement support mechanism facilitates safe and easy grinding wheel and flange changeovers.
The machine’s FANUC 31i-B control features a 375mm touch panel LCD with the newest HMI (Human Machine Interface) technology. Users can move the panel to where it is most convenient to operate.
Mitsui Seiki USA chief operating officer Bill Malanche said, “The GSH 200A combines high performance with flexibility and solid accuracy. It is a highly-productive workhorse thread grinding machine for a wide variety of applications.”
Related Glossary Terms
- centers
centers
Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.
- coolant
coolant
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
- cubic boron nitride ( CBN)
cubic boron nitride ( CBN)
Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.
- dressing
dressing
Removal of undesirable materials from “loaded” grinding wheels using a single- or multi-point diamond or other tool. The process also exposes unused, sharp abrasive points. See loading; truing.
- feed
feed
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- grinding
grinding
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
- grinding machine
grinding machine
Powers a grinding wheel or other abrasive tool for the purpose of removing metal and finishing workpieces to close tolerances. Provides smooth, square, parallel and accurate workpiece surfaces. When ultrasmooth surfaces and finishes on the order of microns are required, lapping and honing machines (precision grinders that run abrasives with extremely fine, uniform grits) are used. In its “finishing” role, the grinder is perhaps the most widely used machine tool. Various styles are available: bench and pedestal grinders for sharpening lathe bits and drills; surface grinders for producing square, parallel, smooth and accurate parts; cylindrical and centerless grinders; center-hole grinders; form grinders; facemill and endmill grinders; gear-cutting grinders; jig grinders; abrasive belt (backstand, swing-frame, belt-roll) grinders; tool and cutter grinders for sharpening and resharpening cutting tools; carbide grinders; hand-held die grinders; and abrasive cutoff saws.
- grinding wheel
grinding wheel
Wheel formed from abrasive material mixed in a suitable matrix. Takes a variety of shapes but falls into two basic categories: one that cuts on its periphery, as in reciprocating grinding, and one that cuts on its side or face, as in tool and cutter grinding.
- numerical control ( NC)
numerical control ( NC)
Any controlled equipment that allows an operator to program its movement by entering a series of coded numbers and symbols. See CNC, computer numerical control; DNC, direct numerical control.
- steady rest
steady rest
Supports long, thin or flexible work being turned on a lathe. Mounts on the bed’s ways and, unlike a follower rest, remains at the point where mounted. See follower rest.
- threading
threading
Process of both external (e.g., thread milling) and internal (e.g., tapping, thread milling) cutting, turning and rolling of threads into particular material. Standardized specifications are available to determine the desired results of the threading process. Numerous thread-series designations are written for specific applications. Threading often is performed on a lathe. Specifications such as thread height are critical in determining the strength of the threads. The material used is taken into consideration in determining the expected results of any particular application for that threaded piece. In external threading, a calculated depth is required as well as a particular angle to the cut. To perform internal threading, the exact diameter to bore the hole is critical before threading. The threads are distinguished from one another by the amount of tolerance and/or allowance that is specified. See turning.
