19-Precision Evolution February 15, 2024
This tool that was developed by Percy Root in the early 1900’s for use on our original reel grinders. It measures off the reel shaft using a stop. It was more than adequate for the conditions at the time and has been copied by other grinder manufacturers for the last century. I added a dial indicator to it in 1991 which helped improve the precision.
The problem with measuring one end at a time is that point you would measure on the shaft was not the focal point of the adjustment resulting in both ends of the reel shaft moving whenever you made an adjustment. This required you to go back and forth until both ends read the same. In 1994 I developed the above tool, the dual dial indicator alignment tool. Before you placed the reel on the precision surface of our Peerless 2000 Reel Grinder, you would calibrate it with two 1-2-3 blocks, setting both indicators to zero. A 1-2-3 block is a precision ground block that is 1 inch by 2 inches by 3 inches. Once calibrated, you would place the reel on the grinder then place the alignment tool on both ends of the reel shaft. you would then adjust the front roller until both indicators had the same reading. This was a big improvement because you only had to make the adjustment once.
Just one problem. You would be measuring off of the reel shaft. That was okay up until the 80’s but increasing demands and lower height of cut made this technique obsolete. I was doing a demo on an old Toro with a .030” eccentric adjustment on the bed knife. I did not find out until after I was done grinding that the reel shaft had about a .060” wobble in it so I had ground a cone into the reel of more than .030”. This meant that the bed knife ran out of adjustment before it would cut all the way across. That was the last time I measured off of the reel shaft. I stopped at the first hardware store I could find and bought a seamstress tape and had better results. I then bought a Pi Tape® but it is made of spring steel and would vary wildly depending on how hard you pulled on it. So I merged the two and came up with our patented Reel Diameter Tape™. A simple device that is the most precise, least expensive you can get for measuring reel diameter and shape.
*Pi Tape® is a registered trademark of Pi Tape Texas