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Do-it-yourself Gun Drilling

Linear-displacement transducers may have changed over time, but you still have to bore a hole down the center of the cylinder’s piston rod to accommodate the stationary portion of the LDT.

Integral mounting of a linear-displacement transducer (LDT) has become a widely used method for providing electronic feedback of stroke in hydraulic cylinders—and for good reason. Mounting an LDT inside a cylinder provides a compact package and, more importantly, protects the transducer from hazardous environments. Impact from heavy objects, abrasive materials, corrosive solutions, and other hazards can’t get at the sensitive parts of a transducer if they are embedded within the relatively safe confines of the cylinder.

The transducers themselves have evolved over the last 30 years or more since in-cylinder mounting started catching on. Designers now have a wide variety of analog and digital outputs to choose from, and the electronics of LDTs have become more rugged, making them more tolerant of shock and vibration. But one thing hasn’t changed: having to bore a hole down the center of the cylinder’s piston rod to accommodate the stationary portion of the LDT. Some proprietary designs get around this, but having to “gun drill” the piston rod has become a given for most applications where integral mounting of the LDT has been specified.

This deep-hole drilling unit can bore a hole up to 12-mm in diameter and 1,200-mm deep in a piston rod to allow mounting a linear-displacement transducer inside a cylinder.

The practice has become fairly routine for many machine shops, but if you make your own cylinders, it’s another step in the product process that involves placing an order, tracking shipping and receiving, and following up if something goes wrong. If you make quite a few of your own cylinders, another alternative could be to acquire your own deep-hole drilling machine.

Traditional deep-hole drilling machines can be expensive and difficult to operate, but Somex, a member of the Suhner Group, now offers customized deep-hole drilling machines capable of boring up to 12 mm diameters and as deep as 1,200 mm. These modules can be integrated directly into transfer machines, special-purpose machines, or conventional machines, such as turning machines. Somex routinely conducts tests with actual tools and materials to verify a machine’s design and performance. Tests are done at the factory using specific production tools under real production conditions.

Traditional deep hole drilling typically requires either a pilot-drill 1½ times the diameter or a drill guide bushing, which is then followed by the deep-hole drilling process. The Somex design, however, combines the guide bushing with a chip basket, allowing both items to travel in unison. The movement of the guide bushing is air-driven, which helps provide closer contact to the part while preventing coolant from escaping. Longer deep-hole drilling applications may require incorporating a support bushing to stabilize the deep-hole drilling tool.

For more information, visit Suhner Industrial Products, Rome, Ga.

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