Removing Broken Pieces
Page 78
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BROKEN taps, reamers, drills. set screws, pins or dowels firmly fixed in their holes can be removed without risk of damage to the hole with the newly introduced Dohm Disintegrator.
Spark erosion is used with this machine to destroy the core of the broken part so that it collapses. This is done without rotary cutting, chipping or any other form of mechanical action, so that there is no danger of damage to the original hole, even where it is threaded.
The equipment consists of a power unit, a work head, which is connected to the power unit and to a water supply, a hollow electrode, fitting into the work head, an earth clamp, and a special stand. A splash guard and sump are also supplied.
Where large and heavy castings or forgings are involved, the machine can be taken to the job.
In operation, the appropriate electrode is fitted to the work head and with the power switched on, and the water running, the operator makes electrical contact between the electrode and the broken tool, the water acting both as a coolant and to wash away the disintegrated particles.
Various sizes of electrodes are available for use with different hole sizes—the standard range covering 1.1.6. in. to I in. The equipment is said to work equally well with ferrous and non-ferrous metals, and there is no transfer of heat to the casting or forging and, consequently, no risk of affecting the hardness or temper of the part.
As an indication of the rate of operation, the Disintegrator is claimed to remove a ile,-in.-diameter high-speedsteel tap, +-in. long in 1 minute 35 seconds.
Full details are available from Dohm, Ltd., 167 Victoria Street, London, S.W.1.