CLEAN IT UP AND WRING IT DRY

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CLEAN IT UP AND WRING IT DRY George Schuetz, Mahr Federal Inc.  There’s probably nothing in your shop that is made to the same high level of precision as your gage blocks, with their manufactured tolerances closer than a few millionths.  The Hubble Space Telescope gets mirror envy when it thinks about the smoothness and accuracy of a common gage block.  It requires just a few, but nonetheless important, care and maintenance measures to retain that extraordinary precision for years.  Cleanliness is critical; it is Rule Number One.  Never wring, or use in any other way, gage blocks that have been exposed to chips, dust or dirt.  Blocks that have been exposed to cutting fluids must be cleaned, without fail, prior to wringing, or the metal particles held in suspension will surely wear the blocks’ surfaces.  To clean blocks, use filtered kerosene, a commercial gage block cleaner or some other high-grade solvent that doesn’t leave a residue.  Wipe them dry with a lint-free tissue.  Even if you are taking “clean” blocks from their storage box, clean them again.  They’ve probably picked up lint or dust while in the case.  Wring blocks together “dry.”  Rubbing them on your palms or wrists will deposit oils that may assist in bonding the blocks during a wring, but it may also transfer dirt and moisture that can damage the surfaces.  If you can’t get a good wring dry, use a commercial wringing solution, available at most trade stores.  Don’t allow gage blocks to remain wrung together for long periods, because they can become permanently fused to each other.  If you use the same setup day after day, make sure you separate and then wring them daily.  Frequently inspect the blocks for nicks, scratches or burrs, and repair or replace any damaged blocks before using them.  One advantage of combining blocks by the method described in last month’s column (by “zeroing” the dimensions in order, from the smallest decimal place to the largest) is that wear is randomly spread among the entire series of blocks.  But if even one of those blocks is damaged, then you will end up randomly transferring scratches among your entire collection.  When you are through, make sure you always clean the blocks before putting them away in their case, and coat them with a non-corrosive oil, grease, or a commercial preservative.  If you don’t coat them, they will rust, even in the box.  Just think what corrosion will do to the surface of blocks when you are wringing them.  Regard the case as part of the working system of gage blocks.  Return blocks to the proper slot in their case as soon as possible.  Beyond protecting them from dust, the case ensures that the blocks don’t get tossed haphazardly in a random box, where they can easily damage one another.  The labels on the case are much easier to read than the numbers etched on the blocks themselves, so you will spend less time looking for the right block.  And you will be able to see immediately from the empty slots what blocks are in use or missing.  Keep the storage case scrupulously clean, both inside and out.  This will serve to remind you and other users that the gage blocks are not just hunks of metal.  We are talking precision instruments here, and they must be treated as such to retain that precision.  Finally, don’t loan out individual blocks.  The minute a set is broken up, all of the above points are likely to go for naught.  You can no longer control the conditions under which those blocks may be used, and they may return to haunt you by transferring dirt, corrosion, or scratches to your other blocks.  That is, of course, if they return at all.