Return to Bearing Replacement Article

This is a brief discussion of how to
bore the declination bearing holes to
receive the needle bearings.

Both fork arms can be removed from the telescope and the bearing holes bored open to receive the new needle bearings.  The original holes are nominally 1.1 inches in diameter. Each of these holes has a nylon insert which should be removed and discarded.  Clean the residual grease from the bearing hole.  The fork arm can be mounted as shown in the photo on the flat bed of a small milling machine.  The existing hole should be carefully centered under the milling spindle.  A boring tool should be used which is set to a diameter of 0.003 inches under the outside diameter of the needle bearing to be used.  The bearings I used were 1.330 OD.  I used a fly cutter set to 1.3 inches.  The setup with the cut started can be seen in the photograph.

The Aluminum casting used for the fork arms is soft and very easy to cut.  There are however lots of voids.  These do not affect the outcome.  After the arm is bored, I used a bearing scraper (hone is ok) and opened the holes to fit the bearing snugly but to a finger push fit.  This took just a few minutes of scraping.


The photograph below shows the bearing partly inserted into the fork arm opening.  After it is confirmed that the bearing is a smooth fit, it can then be coated with medium loktite (blue) and pressed into place with the inside surface flush to the fork arm. Once this is done, the bearing must be firmly packed with grease and the telescope is ready for reassembly.

The bearing replacement operation turns out to be a very easy to accomplish.  I have done both a 10" and a 12" LX200 with absolutely no problems.


Return to Bearing Replacement Article

Go to Home Index for Doc G's Info Site