TR3 (IADC  1-2-1)
  Soft to Medium Formations
The TR3 is the fastest drilling bit produced by Throop. This bit model is designed with long "A" shaped teeth, widely spaced and fully hard faced from crest to root for maximum penetration rates. In formations that range from moderately soft to medium soft. This design is most effective in formations with compressive strengths under 5,000, such as shale, clay, red bed, medium limestone and unconsolidated formations. The TR3 also features the absence of deletions on the gage side of teeth on the heel row of the number two cone. This insures maximum gage life along with tooth life in more abrasive formations.
Effective operating weights are from 1,000 to 3,000 pounds per inch of bit diameter with corresponding rotary speeds of  200 to 50 RPM. 

 

TR2 (IADC  2-1-1)
  Medium to Medium Hard Formations
The TR2 offers the combination action of chipping, crushing and gouging/scraping provided because of reduced cutter offset.  The teeth are shorter "A" shaped and more closely spaced teeth than those of bits designed for softer formations. Long crests in the outer row teeth have self sharpening hard facing applied for maximum penetration and longer bit life. This design will most economically drill medium and medium hard formations and was designed to replace the softer formation bits in the strata where shale alternates with streaks of limestone and sandstone or where gypsum tens to ball up between the teeth.
The most effective weight range varies from 1,000 to 5,000 pounds per inch of bit diameter, while rotary speeds of 150 to 50 RPM give best performance. Rotary speed should be decreased as weight is increased.    

TR1T (IADC  3-1-1)
  Medium Hard to Hard Formations
The TR1T operates best in hard abrasive formations such as hard sandy limestone, limestone interspersed with cherty streaks, broken shale, dolomite, granite, and abrasive sand. This bit is especially constructed to withstand the stresses imposed in drilling hard formations under heavy weights. The gage teeth are "T" shaped and hard faced with tungsten carbide. There are no interruptions on the heel row teeth and the inner row teeth are short and closely spaced for maximum strength. Other features include balanced bearing design and extra thick cone shells. The most economical bit performance is obtained with weights of 3,000 to 8,000 pounds per inch of bit diameter. Corresponding rotary speed should range between 100 and 40 RPM. It is recommended practice that the rotation speed should decrease when increasing drilling weight.  

TR1H (IADC  3-2-1)
 Very Hard Formations
Hard, abrasive formations requiring maximum resistance to gage wear are best drilled with the TR1H bit. The bit provides the necessary chipping and crushing action on bottom and drills efficiently in formation such as siliceous limestone, dolomite, sandstone and granite. The gage surfaces of the cones have webs joining adjacent heel teeth, which insures great resistance to wear. Inner row teeth are short and closely spaced to withstand maximum stress.
This bit is designed to drill most efficiently in hard formations with weights ranging from 3,000 to 8,000 pounds per inch of bit diameter. Rotary speeds should decreases from 100 to 40 RPM as weight is increased.