I picked up a Blue-Point air ratchet from an estate sale a couple weekends ago for $5. I knew it had some kind of issue because the throttle lever laid flat against the body as opposed to sitting away from it like normal. For $5 I decided to pick it up.
Once I got home, I hooked the air ratchet up to my compressor and the ratchet immediately started spinning. It spun up but didn’t really go that fast. I put a socket on it and used it to drive a nut down. The air ratchet got the nut pretty tight which told me it was in good condition. I looked over the air ratchet to try to find a part number but couldn’t. Odd. Reviewing it again, I noticed a small hole and stud on the “neck” of the air ratchet where a tag may have once gone. I also found a Snap On date code on the end of the air ratchet in the shape of a “M” missing a leg. You can see it in the picture above. With all the info, I headed in to look around online.
I headed to Snap-On’s website, as they’re the owners of Blue-Point, and discovered that Blue-Point still makes an air ratchet that looks very similar to mine. The current model is the AT700F. They also had a parts diagram which would be useful soon. I looked up the date code and it showed my air ratchet was made in 1985.
I decided to disassemble the air ratchet to clean and figure out what was wrong. It came apart pretty easily. There’s a large nut in the middle that separates the air ratchet into two pieces: head and body. The body was disassembled by removing the planetary gear assembly, threaded ring, and drive assembly. The ring was very tight and required the use of some large Channellocks with some rubber to keep from damaging the threads. I also disassembled the trigger mechanism and immediately found the problem. The valve was missing. The lever pushes down a pin which should push the valve down allowing air to flow. On the other side of the valve is a spring that pushes the valve back closed as the lever is released.
The part I’m calling the drive assembly contains the rotor and vanes. I separated the rotor from the top bearing and found it to be pretty clean inside as can be seen below. The rotor has vanes which loosely fit in the rotor allowing them to slide in and out. The rotor fits inside the cylinder which has a hole in it that is off center. As a result, at one point around the cylinder the vane is pushed completely into the rotor and 180 degrees away a vane is fully out. Thus, as air comes in it presses against the vanes spinning the rotor and driving the tool.
I cleaned the drive assembly with some degreaser and oiled it before reassembly. The rest of the parts were looked over, cleaned, and oiled or greased as was appropriate. I don’t have any pictures of it but I also disassembled the head. There’s a snap ring on the bottom around the ratchet assembly that can be removed to take it apart.
I looked around further online and found a description of the missing piece. It was described as a T shaped part. That makes sense. Snap On, as always, has parts you can buy to repair their tools. My valve was available from them for $4.95 which would almost double the cost of my air ratchet. Can’t have that. So, I did some measuring and came up with a design for a replacement valve. I whipped it out on the lathe pretty quickly. The metal stock I had which was closest to the max diameter of the part didn’t turn that well and left a bit of a rough finish. I had a small peg from parting the piece off and ended up leaving it on. It doesn’t interfere with the valve functioning correctly and simplifies installing and removing the valve.
Below is the throttle assembly. The pin can be seen inside the hole in the bottom of the air ratchet.
I put it all back together and now have an air ratchet that doesn’t run all the time. Yay. I tested the air ratchet tightening and loosening some nuts and bolts. It seems to operate as expected and has good power. I also found out from the specs online that the air ratchet’s free speed is 165 rpm which explains why it seemed to run so slowly. The next day it was great to have the air ratchet while removing the numerous bolts holding on my transmission pan.