Introduction: Sears Radial Arm Saw Upgrade
My Sears radial arm saw was made in May 1972. It was about to be replaced by an upgraded model. The chief difference between mine and the upgraded model was the motor carriage suspension track on the arm. Mine used a milled “V” in both sides of the arm. Carrier bearings with a convex face rolled against the sides of the “V” channels.
I recently added the “newer” steel rod ways with the new style concave bearings to my older saw. I had thought about doing that for a long time. The tipping point in my decision came after I did a lot of work with a wire wheel. The wire wheel I bought from Sears when the saw was new was US made and very well balanced. The replacement wheel I bought many years later carried the name of a respected US toolmaker, but was made in China. It was not balanced. The motor carriage was not securely locked down on the arm and the out of balance wire wheel beat a bump into my cast iron arm before I realized what was happening. I tried a couple of sound approaches for getting rid of the bump, but they were not satisfactory. I went shopping on eBay and bought the Craftsman steel rods needed for the ways and the matching concave bearings.
The photo shows the “new” rod ways and concave bearings on one side of the saw arm. The second image is a drawing of the original "V" channel on the arm and the convex bearing. The third image shows the machined rod in the "V" groove with the newer concave bearings.
Step 1: Drill and Tap for the Steel Rod Ways
Use a suitably sized clamp to hold the steel rod ways in place in the "V" channels. Drill and tap for hex socket screws to hold the steel rods in place. I bought the screws at a local hardware store. While there is a recess for the screw heads, the motor carriage bearings will not slide over them. I tried grinding the heads to fit the contour of the steel rods, but was beginning to grind away too much of the hex sockets. When I must remove the motor and its carriage from the arm, I clamp the rods as in the first photo, and remove the screws.
Step 2: My Big Surprise
I always imagined this upgrade would be only a matter of removing the bolts with the original bearings and putting the bolts back with the new bearings. No, the distance between the bolts with the old bearings is narrower than with the steel rod ways and the new bearings. I made some errors, but you will benefit from what I learned.
The distance between the centers of the original holes for the old bearings was 4.67 inches (118.6 mm). The distance between centers on the new bearings is 5.33 inches (135.4 mm). Two of the bolts have a cam for adjusting the tension of the bearings against the steel rod ways. There is some tolerance for error, but not much.
As noted in the text boxes on the photo, I had to add two washers between the motor yoke and the bottom of the new bearings. See the text boxes in the photo.
Step 3: The Carriage Lock
I had to make some adjustment to the thin steel that is between the carriage lock screw (used for rip cuts) and the cast iron arm. Mine was also wearing from decades of use. Because I have a welder, I welded a thin piece of steel the same gauge over the spot where the locking bolt screws against the thin steel. I removed the motor carriage from the saw arm. Then I separated the upper part of the carriage from the lower part. I used a punch and a hammer to drive out the body of the carriage lock. See the text boxes.
Step 4: Minor Adjustments
I put the carriage with the new bearings onto the new ways. I tightened the cam bolts to make them snug, but was careful not to overtighten them. Still, the carriage moved smoothly over most of its travel, but was too tight at the column end. I decided to stroke the rod ways with an oilstone. It made a big improvement. I removed so little material that it probably does not matter if I removed material evenly on both sides, on top and bottom, etc.
Step 5: Decorative Covers
I want to use the decorative covers that came with the saw, but I need to make cutouts to make space for the new bearings. I may shape sheetmetal enclosures to fit over the bearings where they extend outside the old decorative covers and attach those covers with short sheetmetal screws. (I still have the mounting hardware, although it was removed for these photos.)
I like the smoothness of the motor carriage as it slides on my newly improved Sears radial arm saw.
An afterthought—I looked more closely at the original carrier bearings. Turning them with my fingers shows they feel rough, as if dry or nearly worn out. And, it was 35 years ago that I had replaced the motor bearings. I tried removing the seals and packing them with new grease. There was some damage to the seals in the process. I have ordered new motor bearings. Nothing is forever. These saws are great, but bearings do dry out and do wear out. If there is or may be one of these saws in your life, give some consideration to the condition of any ball bearings on the tool,