The free-wheel parts electrolytic-polished is of great use for the decrease of rolling friction and increase of anti-corrosion.
This report describes the following items.
(1) Design and trial manufacture of special jig which is able to polish all parts of these somewhat complicated rings at one time.
(2) The result and proceeding of experiment for mass production by the apparatus with the above-mentioned jig and electrolytic solution consisting of orthophosphoric acid-acetic anhydrid-gelatin.
(3) and others.

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Researches on "electric spark machining" by mechanically up and down vibrating electrode were made with the circuit used by Dr. B. R. & N. I. Lazarenko (U. S. S. R) (fig.1). As shown in fig.2, the vibrating electrode and its holder are nearly balanced with a counter-weight, so with the advance of machining, the vibrating center of electrode, i. e. its holder, descends automatically, and machining is made automatic simply. With this automatic machine, the conditions to raise the machining speed were sought, when the work pieces of mild steel were machined in a dielectric fluid bath of petrol chiefly. The main results obtained are as follows.
(1) The smaller the sectional area of electrode is, the shorter the necessary working time becomes.. So it is preferable to use a hollow electrode. And it is otitable that the wall of electrode is made 1. 5mm thick. (fig.3 & 4)
(2) The maximum working speed can be obtained, if the counter-weight is adjusted so that the mean working current may show 30, -40% of the short current V_o/R (fig. 5).
(3) The greater the frequency of electrode vibration is, and the smaller the amplitude of electrode is, the faster the machining speed becomes (fig. 6). By this fact, the machining efficiency may be better, when the electrode is not vibrated.
(4) Unless "arc discharge" takes place, the smaller the resistance R in charging circuit is, the faster the working- speed becomes (fig.7).
(5) For the electrode material, brass is the best, and copper follows (Table. 1).
(6) For the dielectric fluid, whale oil, petrol and rape-oil are good, but from the view point of easy filtering of used oil, petrol is the best, and water is also useful economically (Table. 2).

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