Fi 21 \ hob-grinding uachine oi 1933, showing 



use of the master screw with .1 cnodiftei but without 

 ch;m u Carl G. Olson's \ V patent 1901926. 



Figure 22 A mm -bak di \ ti 1 to modify the effective lead 

 of a master lead screw without introducing a complex 

 mechanism which would be both difficult to make and 

 to operate within the required close limits. Carl G. 

 1 Hson • 1933 1 S patent 11101926. 



longitudinal movement ol the spindle, .1 tool holder for 

 supporting a grinding wheel in operative position with 

 respect to the work supported b) the spindle during the 

 and longitudinal movement thereof 



Even before this patent was applied for, another 

 patent was pending for- the purpose of modifying 

 the pitch of the lead screw without the use of change 

 gears in spite of the wide acceptance of such gear 

 mechanisms for over a hundred years. 



Figure 21 shows a plan view : of the machine, and 

 figure 22 a detailed view of the sine-bar mechanism 



actuated In the mastei screw, 6, to 1 lif) the 1 ffi 



pitch of the lead screw in accordance with the realities 

 of practice as Mated in the preamble of the p; 



I his invention relates to material working machines, 

 and particularly to machines sui h as hob 

 and the like, wherein the work is reciprocated through 



the agency of a lead screw. 



1 S patent 1901926, filed February 16, 1928, issued to 

 1 G Olson of Chicago, Illinois, March 21, 1933, and assigned 

 to the Illinois Tool Works, also of ( I 



PAPER 37: SCREW-THREAD CUTTING BY THE MASTER-SCREW Ml rHOD 



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