Thomason 1965, p. 53: "The sleeve, endplates, and cylinder were constructed of beryllium with machined tolerances of 20 micro inches in roundness and 20 micro inches/inch in squareness." Thomason, Herman E. (September 1965). General Description of the ST-124M Inertial Platform System (Report). NASA. hdl:2060/19650024833. NASA TN-D-2983; 65N-34434. This has clearer figures than most of the PDF documents about the IU, providing the best views of the insides of the gyros and gas bearings.
Thomason 1965, p. 53: "The sleeve, endplates, and cylinder were constructed of beryllium with machined tolerances of 20 micro inches in roundness and 20 micro inches/inch in squareness." Thomason, Herman E. (September 1965). General Description of the ST-124M Inertial Platform System (Report). NASA. hdl:2060/19650024833. NASA TN-D-2983; 65N-34434. This has clearer figures than most of the PDF documents about the IU, providing the best views of the insides of the gyros and gas bearings.