1953 年 69 巻 780 号 p. 199-202
As the arst step to determin6 the workability of coal face underground, resistant forces to cut the coal blocks taken as samples were measured by our newly designed resistance lndicator. From that experimental results, we learned that the amounts and the properties of two components of the cutting resistance force-nalnely the main and the subordinate components. Then these values were compared to the hardness of the coal, obtained by a Screlometer as well as by our own designed hardness.tester. By these, we found that the properties shown by the three measurements closely consist.