Blocks should be free from dirt, nicks, burrs, and corrosion before being used. Nicks, burrs,
and light corrosion may be removed by stoning the blocks. (See procedures for stoning gage
We recommend washing gage blocks in mineral spirits. Chlorinated solvents should be avoided
because of their health hazards. Alcohol is not recommended because it is a fire hazard and it
may leave the blocks so clean they may be susceptible to corrosion. Mineral spirits leaves a
slight oily film that provides some short-term protection against corrosion. This slight film does
not interfere with the use of the blocks.
Place the blocks in a shallow pan that is either made from stainless steel or is porcelain lined.
The pan should be deep enough to completely cover the gage blocks. At the bottom of the
pan, we recommend a waffle rubber mat to protect the blocks from scratching. The mat will
keep the blocks away from dirt and grit that may collect at the bottom of the pan.
Allow the blocks to soak in the mineral spirits for several minutes before proceeding to allow the
solvent to soften any caked-on dirt and grease.
Use a soft bristle brush to remove any heavy grease or oils from the surfaces of the blocks.
Then wipe the blocks with a soft cloth to remove any remaining dirt or grease and to dry the
blocks. No dirt should show on the cloth.
In addition, the through hole for square gage blocks needs to be thoroughly cleaned. A small,
thin bottlebrush can be used for most blocks up through 4 inches. For longer blocks, a gun-
cleaning rod for a .22 caliber rifle is very useful. Allow square blocks to sit upright on a soft
cloth for several minutes to allow any excess solvent to settle out of the hole.
Allow enough time after washing the blocks for the blocks to thermally acclimate before using
the blocks. (See Recommend Thermal Acclimation Time.)