Railway and Locomotive Engineering . econd section of the Su-perior Council of Waters, and which willsoon be submitted for the financial ap-proval of the Council of Administrationiof the railways. September, 1921 RAILWAY AND LOCOMOTIVE ENGINEERING 255 New Method of Making Hollow Drill Steel There are various methods of makinghollow drill steel. That in general usein the country is to use a drilled billetwith a sand filled core. Another sys-tem, which is that generally used inSweden, is to roll the drilled or piercedbillet over a projectile or ball as inordinary pipe manufacture. In the Swedish
Railway and Locomotive Engineering . econd section of the Su-perior Council of Waters, and which willsoon be submitted for the financial ap-proval of the Council of Administrationiof the railways. September, 1921 RAILWAY AND LOCOMOTIVE ENGINEERING 255 New Method of Making Hollow Drill Steel There are various methods of makinghollow drill steel. That in general usein the country is to use a drilled billetwith a sand filled core. Another sys-tem, which is that generally used inSweden, is to roll the drilled or piercedbillet over a projectile or ball as inordinary pipe manufacture. In the Swedish material, a peculiarcondition is present. The hole is badly end, as shown in the engraving and thencogged down to billets about 2j/2 They are then cleaned, chippedand reheated and rolled to the size of thefinished bar. In the case of a 1-in. hexa-gon, for example, this leaves a hole 5/16in. in diameter. After rolling, the bars are cut to therequired length and the sand extracted bymeans of a sand blast working at a high. PLUGGED HOI-LOW IXGOF READY FOR ROLLING decarbonized by the method of manu-facture. A question that seems worthy ofdeep consideration is this: Is this de-carbonized core an advantage or dis-advantage? If it is an advantage, whynot duplicate this by controlled prac-tice and not haphazard means of manu-facture? If it is a disadvantage, whythen is it that steel of this character hassuch a good reputation for being a goodgrade hollow drill steel? There is noth-ing in the steel that can be discernedmicroscopically or by analysis thatproves it to be superior to hollow drillsteel of good manufacture made bymethods that prevent decarbonizationof the hole. Therefore it is fair toassume that the decarbonized wall ofthe hole is an advantage. On investi-gating this subject it was found that hard-ened bars with this decarbonized holedo not become so intensely hard on theinside, neither are they so prone tocracking. Bars with radial cracks areof course bad, no m
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