End view showing involute groove 98 Machinists' Levels with Ground and Gradua ted Vials 4-18"/100-450MM These levels have ground and graduated main vials. All sizes have a cross test vial except the 4" (100mm) model. The 12" (300mm) model also has a plumb vial and the 18" (450mm) size has a double plumb vial. These vials are adjustable to a positive setting and are housed in a satin chrome finished brass tube with a friction-fit closing cover to prevent breakage. The base of the levels features an involute groove running the length of the base, which provides a reliable seat for round work such as pipes or shafting. With the cross test vial, it is possible to simultaneously level in both directions. This prevents inaccuracies in the main vial reading caused by canting the level sidewise on round work. The 6" through 18" (150-450mm) main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42mm per meter). There are five, six, or seven lines on each side of the bubble, depending on the base length. Machinists' Levels 98 Machinists' Levels with Ground and Graduated Vials Without Case In Finished Wood Case Tube and Plug Assemblies Size Description Cat. No. EDP Cat. No. EDP Part No. EDP in mm 98-4 50440 4 100 Without cross test vial 98-6 50441 PT99430 64497 6 150 With cross test vial 98-6 W/SLC 66935 With cross test vial, Standard Letter of Certification* 98-8 50442 PT99431 64498 8 200 With cross test vial 98-12 50443 98Z-12 50444 PT99432 64499 12 300 With single plumb vial and cross test vial 98-12 W/SLC 66934 98Z-12 W/SLC 66933 With single plumb vial and cross test vial, Standard Letter of Certification* 98-18 50445 98Z-18 50446 18 450 With double plumb vial and cross test vial To guarantee extreme accuracy, the length of your level should not be longer than the work you are leveling. * Includes redemption card for Standard Letter of Certification (SLC) 371 starrett.com M achinists ' L evels