Micrometer Reconditioning Tools — Flat Parallel Lapping Tools

It is a well established fact that gray cast iron is a superior material for use as a lapping tool. Flat parallel disks of gray cast iron are used to recondition the worn surfaces of the anvils and spindles, of micrometers, and the parallel measuring surfaces of laboratory measuring machines.

It is desirable to have these gray cast iron disks large enough to give a reasonably long service life, but they should be small enough to be easily manipulated by hand. The Bal-tec flat parallel lapping tools are standardized at two inches (2.0”) [50.8mm] outside diameter. These tools are lapped flat and parallel within less than twenty millionth of an inch (0.000020”) [0.5 micrometers].

The large surface area of these two inch diameter tools is so great when compared with the small area of the end of a micrometer spindle that the spindle and anvil of the micrometer sees almost perfect geometry. To recondition a micrometer, the yoke or frame of the micrometer is clamped in a vise. It is a good practice to put several layers of paper between the micrometer frame and the jaws of the vise.

In use, a thin layer of three micron diamond lapping compound is applied to one surface of the parallel lapping tool that doesn’t have the small letter “B” marked on it. Never apply lapping compound to the “B” surface. Apply a very light pressure by closing the micrometer or measuring machine on the lap gently. You should still be able to move the lap between the micrometer-surfaces without having to use much force.

Draw the cast iron lap back and forth between the surfaces of the spindle and anvil in a figure-8 motion. Try to use the entire surface of the lapping tool to spread any wear that results evenly over the entire surface of the lap. Periodically remove the lapping tool and inspect the spindle being lapped. When the micrometer-surface being lapped appears to have cleaned up 100%, remove all the diamond compound from the spindle and the lapping tool with a tissue wetted in isopropyl alcohol. This will leave an invisible layer of diamond shards embedded in the surface of the lap the first time you do it.

Put a drop of light oil on a piece of tissue paper. After the oil on the piece of tissue has soaked in for a few minutes, touch the oil spot with one of your fingers and rub the dry surface of the lap until it changes color. Do the same to the other side of the lap. This coats the lap surfaces with a minute layer of lubricant, so the lap will slide smoothly between gage surfaces. Now use the diamond-charged surface of the cast iron lap only to finish-polish the micrometer, or measuring machine, surfaces.

Use the same procedure to lap the other micrometer surface by flipping the lap around.

WARNING: Never apply any diamond compound to the “B” surface.

Please see also, our web page: "The 8 inch Diameter Flat Lap."

The price is $137.50.

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