Mark42

I have a few of the old "blue" Ryobi 14 and 18 volt tools and regularly clean and lube them. I noticed that most of the 5 1/2" 18 volt circular saws have half of the gear case cast metal, and the other half is the blue plastic housing that also supports the large ball bearing of the blade shaft. The exception is the R10631 model. It has a different motor, about 25% more gear tooth contact, and a full metal gear case (both halves) that incorporates the big bearing and screws to the plastic housing. So the R10631 drive train from the motor to the blade is entirely comprised of metal parts that sit in the plastic housing. Compare that to the P501, R10632, and R10633 that all support the big bearing with the plastic housing, half the gear case is the plastic housing, allowing flex of the gear box and misalignment of pinion and shaft gears under load. I can not find any documentation that describes why the R10631 is a better design, or it being a heavy duty model, etc. Also noticed that the R10631 is the only model without a red RYOBI label on the blade cover. Instead RYOBI is cast into the aluminum blade cover and is aluminum color. Anyone know why this model was manufactured with a better gear case and drive train? Thanks, Mark. R10631 two piece totally enclosed gear case. P501, R10632, R10633, etc gear case. RYOBI emblem is cast into blade guard in R10631.