The Bridge and Joint Micrometer (BJM) was discontinued on March 30, 2015. It was manufactured by Equipment Development Services in Schenectady, New York, USA. The information below is only for reference:
Bridge and Joint Micrometers are necessary tools used in turbine alignment and repair. The Joint Micrometer is used to measure the elevation difference between two joints and the Bridge Micrometer is used to measure heights of protruding pins, depths of key-ways, height of keys, etc. The Bridge Micrometers are made in two sizes, the smaller with a 1.50 inch leg opening and the larger with a 4.00 inch leg opening. All micrometers have 1.000 inch travel heads which read in thousandths of an inch.
The bodies of both the Bridge Micrometer and the Joint Micrometer are made of 6061-T6 aluminum alloy and have been hard-coated to approximately 70 Rockwell C to resist abrasion. This gives the tool lightness, which allows excellent tactile feel. They also have hardened and ground replaceable wear pads to ensure long life and accuracy.