Sears Radial Arm Saw: Egg-shaped Indexing Holes





Introduction: Sears Radial Arm Saw: Egg-shaped Indexing Holes

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Sears 10 inch Radial Arm Saws were very popular for many years. The motor yoke is shown below with modifications this Instructable will describe.

The center hole suspends the weight of the motor and yoke from the carriage on the saw arm. The four smaller holes you see in the photo receive the indexing pin to lock the yoke in the crosscut, inrip, outrip and accessories positions.

After years of use the indexing holes become a little oblong or egg-shaped. Some of the holes wear more than others because they get more use. You can align the saw to make an accurate crosscut, but the blade will heel in the ripping positions. I thought for a long time about how I could restore the accuracy of all of the holes. The key was to make each of the three holes used for precision settings (crosscut, inrip, outrip) capable of independent alignment. That can be accomplished with two pieces of strap iron, four 10-32 screws, and four nuts.

For further explanation, imagine you are looking at a clockface in the photo. 12 o'clock is at the top of the photo. The accessory indexing hole is at 1 o'clock. The inrip indexing hole is at the 4 o'clock position. The crosscut indexing hole is at the 7 o'clock position. The outrip indexing hole is at the 10 o'clock position. When you are ready to do the alignment, you will begin with the outrip hole, no matter how much wear it may have endured and how egg-shaped it may be.

Then you will align the strap iron plate you will make that lays above the crosscut indexing hole. Finally, you will align the strap iron plate for the inrip hole.

Step 1: Remove the Motor Yoke From the Saw Arm

Remove the the side covers (plastic parts with the word "Craftsman" on them). Right under the end of the arm is a hex head Allen screw that keeps the motor carriage from rolling off of the end of the arm. Remove it. Carefully cradle the motor in your hands while removing it from the arm. It may be more convenient also to disconnect the electrical cable that goes from the switch to the motor. (The screws in the photo are not factory original. Neither is the on/off switch. My saw was purchased in 1972.) Loosen the spoon paddle (not visible in the photo) that locks the yoke in position and unscrew the threaded plate from the center bolt in the carriage. Lift the carriage from the yoke.

Step 2: Make Two Strap Iron Plates

Use two pieces of strap iron 1/8 inch thick and 3/4 inch wide. They are each 3 7/8 inches long. Drill a 3/8 inch hole in the exact center of each piece. Drill two 1/4 inch holes equidistant from the 3/8 inch hole so they are (center to center) 3 5/16 inches apart.

Grind a concave in one side of each piece of strap iron to make space for the machined ring on the bottom of the motor carriage. You can see a wear pattern from it in the first photo.

Step 3: Drill Mounting Holes in the Yoke

I did this modification a number of years ago. I did not want to disturb my alignments in order to take photos, so I made a drawing.

Put the chuck end of a 3/8 inch twist drill through the hole in one of the strap iron pieces. Insert the same end of the bit into the crosscut indexing hole on the yoke. Press the strap iron down on the yoke surface and turn it so the flat side of the strap iron is parallel to the side of the yoke. Carefully mark the centers of the 1/4 inch holes for drilling holes in the yoke.

Drill holes straight down through the yoke. The holes should be correctly sized for a 10-32 thread tap. Tap threads in the holes. (The drawing shows the holes you will drill. Note the black dots on either side of the indexing holes for the crosscut and inrip positions.)

Place a lock washer onto a roundhead 10-32 screw and thread it up from the underside of the yoke. Tighten it. Do the same with another screw in the other hole. Put a 10-32 nut onto each screw, but do not tighten the strap iron plate down too firmly, yet. Grind or otherwise cut the length of the 10-32 screws so their ends are flush with the top of the nut.

Repeat the process in the previous three paragraphs for the inrip hole and its strap iron plate.

Step 4: Alignment

Put the carriage back together so the yoke is attached to the carriage. Give some attention to how tight to make the threaded plate before putting its set screw back in place. You want the spoon handle that locks the yoke to hold the yoke firmly without over-tightening. Cradle the motor in your hands and slide the carriage back into the roller ways on the saw arm.

As noted in the first step, turn the yoke to the outrip position and drop the indexing pin into its hole. Align the saw so the blade does not heel and kick up splinters at the back end of the blade on either one side or the other.

Move the saw to the crosscut position. You will need to lift the indexing pin a bit higher than before to clear the extra thickness of the strap iron plate. That is a small price to pay for having a very accurately aligned saw again. Align the yoke. You will not use the bolt heads you see in the photo on either side of the indexing pin (center of the photo), even though that was the procedure before your modification. Now you will make your adjustments for the crosscut and inrip positions by loosening the 10-32 nuts on the strap iron plate (as shown in the photo). 10-32 screws are a bit smaller in diameter than the 1/4 inch holes you drilled, so you can move the plates enough to restore accurate alignment. When finished make a test cut and check for blade heeling. It takes some time, but work with the adjustment process until the saw does not heel.

Repeat the process for the inrip position.

You now have a saw that allows you to align independently each of the three indexing holes used for precision setups and cuts.



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    I realize this is a bit late, but I just found out about it myself. There is a free safety upgrade kit for many Sears radial-arm saws available that makes the saw much less scary to use. Check for details.
    I got the kit for my 20-year-old saw. The kit comes with a new blade guard, handle, and as a pleasant surprise, new table boards, which mine desperately needed. It comes with complete instructions that supplement the saw's manual, and installs quick 'n easy. By all means, order and install this kit when you have the saw apart to fix the egg-shaped indexing holes, and it'll feel like a new tool again.

    4 replies

    Thank you for the information. My saw was made in 1972, so it is approaching 40 years in age. Although it was sold without a blade guard, the site you gave tells me no kit is available for my saw. That is after entering my serial number.

    Sorry about that. I'm sure your saw has some kind of blade guard, just not the new, fancy, lawyer-approved one. It even came with an extra part to make it meet OSHA rules for industrial use, but also makes the blade almost impossible to change. I'll only put that bit on if I start a woodworking business and the OSHA inspector twists my arm real hard.

     I should have responded earlier.  My saw has the standardcast blade cover that shields the top half of the blade.  It can betilted so the front rides just above the work piece.  A strong hexrod with anti-kickback paws can be lowered so the paws ride lightly onthe work.  But, it does not have the additional free-moving sideshields of clear plastic or of flat steel.  Those became standard afew years after I got my saw.  As noted below, I keep my hands ahealthy distance from the spinning blade and remain very vigilant whenusing the saw.  I have never had even a "close call."  

    Discussions about blade guards remind me of a radio broadcast I once heard about extra safety features on automobiles, like ABS brakes. While these are designed to provide extra safety margins, drivers felt safer and took extra risks as a result so that the drivers were not safer. If an extra blade guard protects against an accidental encounter of a body part with a spinning blade, that is a good thing. But, if people simply use them to justify engaging in more risky practices, that is not good. I try to maintain a very healthy fear of a spinning blade and keep my hands away from any possible way of being injured. So far I am injury free and hope to stay that way.

    I assume you are talking about welding the strap metal pieces to the yoke and making them permanently affixed. I see three problems with that. 1) Strap iron is mild steel and the yoke on these saws appears to be an aluminum alloy. Those are dissimilar metals that cannot be welded to one another. 2) Anything permanent like welding eliminates the possibility of making further fine adjustments when one of the holes acquires more wear than its neighboring holes and needs to be tweaked. and 3) Even if the metals were not dissimilar and would accept a weld, the process of welding often causes metal to move a little from intense heating and subsequent cooling. Any precision in the adjustment could be lost through expansion and contraction in the welding process.

    sweet instructable man. i dont have a radial arm saw(the only tool i dont have) but this looks like an ingenious fix for a problem :P (carpenters forever!)

    3 replies

    Thanks for your comment. A lot of people have these saws. You may find one for sale at a good price one day and decide to get one. Check my Instructable on Jointing Boards without a Jointer to see another use I get from my radial arm saw. I am always concerned that something in an Instructable I authored will not make sense to the reader. I am glad you found it clear enough.

    I totally didn't realize you were the same person who did the other instructable (i have it favorited), Im always looking for the older power tools (i got a 20 year old power planer and I just had to replace the works better than any new one. lol

    I am relatively new to Instructables and want to find really good Instructables from the past. I have experimented with the Randomizer. That works pretty well. I have also clicked on a poster's name when someone has an Instructable I like to see what other things he might have posted. It is a little like going to a movie unknown to you that has some actors you know have done good work in the past. Anyway, thanks for the positive reception you gave the Instructable on using a sanding drum for jointing. I am trying to post some really useful things I came to over the past forty years.