"Projects" at georgesbasement.com

9. Overhauling a Bausch & Lomb toolmakers microscope protractor eyepiece.
When I received this ex-USAF eyepiece, it seemed to be hopelessly stuck and useless for its intended purpose, so the seller and I struck a deal that I would pay for it only
if I could make it work again without ruining it in the process. This note shows how my successful disassembly and re-lubrication of the eyepiece made it good as new. Whew.

When it arrived, the two knurled rings were stuck.
Eyepiece on a B & L TMM.
Plywood grippers: Bottom at left; Top at right.
Bausch & Lomb TMM eyepiece
Eyepiece on a Bausch & Lomb Toolmakers Microscope
Plywood clamps used to grip the main sections
To see the gummy remnants of the original lubricant, right click the image of the two plywood grippers above.
To remove the bottom section, I used the bottom gripper and a wooden parallel clamp as described below.
The only defect is a tiny chip on the
right angle prism, invisible during operation.
Removing the eyepiece bottom sectionMy first step after removing the vernier reader (shown at right) was to use the grippers to grasp the two knurled rings and then twist them relative to each other, which eventually loosened the top section (the smaller ring at left). Then I used the bottom gripper to grasp the bottom section as shown at left and then simultaneously twist and lift the bottom ring to extract it.  I held the parallel clamp in a heavy vise, which greatly simplified this step.

I applied forces on the order of twenty foot pounds of torque and twenty pounds of axial force.  Making the grippers and disassembling the eyepiece took about ninety minutes.
Vernier reader and other pieces
Before you can separate the bottom section from the body of the eyepiece, unscrew the locking clamp's tiny lever, shown above right.
The scales read in degrees and minutes, with the upper scale ruled in 1/3 steps.
The lower scale is a vernier that divides each 1/3 step into twenty parts.
The bottom's line is the one marked "0".
The bottom also carries the 40 - 70 sector.
The upper section rotates the plain line.
Vernier scale on the bottom section
Vernier scale - different reading
Crosshairs - top section
Crosshairs - different reading
One important function of these crosshairs is to align with the flanks of a screw thread so that the
X-Y table of the toolmakers microscope can be used to measure the pitch and pitch diameter of the threads.

This is an older eyepiece than a second one that I have, which has a cylindrical finger hole.
In this view, the bottom section of the eyepiece is locked in position.
B & L protractor eyepiece in its original box
ASssembled, fully functional TMM eyepiece
The center optics enable the crosshairs of the eyepiece to be rotated to align with the enlarged image of the toolmakers microscope's objective lens,
and the off-axis optics facilitate reading the mirror-imaged and inverted degree wheel of the larger knurled bottom section.

This eyepiece will work on any microscope that has a 23 mm eyepiece tube.  About two dozen cotton Q-tips and 2 cc. of paint thinner were expended in this process.