Progress in Honing-Machines and the Honing Process 280060
CYLINDER finishing by rough and finish-boring with wide tools, which was thought good enough during the first dozen years of the automobile-production period, was supplanted by reaming and grinding. Later, cast-iron and copper laps were used, but all these methods were slow and did not produce the fine finish for which a demand developed.
Experiments were begun about 1920 with the process known as honing. Five years later the company with which the author is connected converted one of its drilling-machines into a single-spindle honing-machine. Other companies made similar conversions. The first honing-head was introduced in 1923.
Not until three years ago, however, did honing begin to be regarded as a real production-method possibility. Since then, very rapid progress has been made and numerous improved machines, honing-heads and honing-stones have been produced. The machines described by the author are driven by electric motors and the spindles are now reciprocated hydraulically by means of an oil-pump and a reciprocating valve-control.
Although honing is a phase of grinding, it has important superiorities, which are described by the author. Wide variation exists among different users of honing-machines in the matter of rotary and reciprocating speeds, but a peripheral speed of 200 to 250 ft. per min, and a reciprocating speed of 50 to 60 cycles per min. are confidently stated to be best.
One great problem has been to obtain stones of the correct grit and composition for the work to be done. Making of the stones is a new process, and uniformity is not yet assured, but conditions have improved within recent months. Considerable experimenting remains to be done along this line.
Honing is declared to be a metal-removing as well as a finishing process, and the latest experiments indicate that honing rough-cast surfaces may become a successful operation. Tests made during the last few months show that steel, in all degrees of hardness from cold-rolled to glass-hard tool-steel, can be honed successfully as a commercial operation.
Many new applications of the process are developing from week to week, and it is being used on a wide variety of work, from finishing steel bushings 1 in. in size to cast-iron cylinders 15 in. in diameter by 3½ ft. in length. Time-saving is one of the greatest commercial advantages of the process, and several examples of its speed as compared with internal grinding are given.
In conclusion the author points out that, for realization of the most successful development of the honing process, cooperation of the makers of the machines, the honing-heads and the stones is necessary.