Custom manufacturing is a significant portion of the workholding business at Hardinge. The company separates custom from standard products in order to better serve the customer: a full staff of manufacturing, design and application engineers, and experienced phone correspondents handle custom product requests exclusively, walking and talking modified and non-typical gripping solutions all day long.
The company manufactures collets for all brands of machines and adapters used in the fastener industry, including precision collets to grip blind bolt fasteners, solid and blind rivets, bolts, screws, nuts, inserts, and studs. A majority of these fasteners are used in the global aerospace market.
Monogram Aerospace Fasteners, a blind bolt manufacturer located in California, turned to Hardinge for a collet that would control part quality and concentricity, at a cost advantage, according to Monogram's VP of manufacturing. One particular job at Monogram involved hard material, cutting off to length, nosing the taper angle, and tapping the fastener body.
“We have many proven collet solutions used in the aerospace fastener industry,” says Tom Mitchell, general manager. “We have provided over-the-shoulder gripping, solutions for non-marking, and can incorporate features such as coolant flushing into the collet design. We will provide microsurface finishes and critical radii with any additional inspections that may be required for the application.”
Gripping Rivets
The over-the-shoulder pickoff collet assembly shown is designed for the manufacture of rivets and is based on a modified 5C collet and ejector stop. This combination enables the customer to take advantage of automation, including robot loading. A flat face and a short bearing allow essential robot gripping access. The rivets are automatically spring-ejected into a parts bin when the collet opens. This design features thru-coolant capability.
The collet shown on the left features three internal tapered cavities to support thru-spindle coolant flushing for boring, drilling or tapping. The gripping surface (order hole) and the locating chamfer at the opening are hard turned to a specified microfinish.
The collet on the right is a 5W over-the-shoulder (over-grip) collet. This design incorporates 6 slots with an oval relief in each slot. The double-angle taper and short bearing surface allow an overgrip to swallow the rivet head in the back drill area inside the collet in order to grip the shaft beyond.
Gripping Blind Fasteners
Over-the-shoulder collets similar to the 5W are used for blind fasteners when required to clear a head and grip on a smaller diameter beyond. Extra spread is required to open the collet wide enough to go over the larger diameter. Hardinge incorporates multiple slots with an oval or teardrop relief at the end of the slots and reduced wall thickness for maximum flexibility to open and close the collet accurately and repeatedly. The relief takes the stress of the wide spread and helps to maintain roundness at the back bearing of the collet. A double-angle taper reduces the contact surface, and allows maximum spread for quick opening of the collet. A back drill area behind the gripping surface (order hole) will accommodate the head of the fastener or screw.
Hardinge’s design and applications engineers will work with other machine tool builders for complete turnkey packages. Along with aerospace, Hardinge supports the automotive, commercial transportation, defense, and industrial markets with these products.