Adapter to Drive Your SBC WVO Gear Pump with a Drill

Does your drill wobble when you use it to drive your SBC WVO gear pump? I have one drill that always works well, but my other drill needs to be secured just right or it wobble right off of the pump. The problem is how the three jaws in the chuck grab the slot in the pump shaft.

I made a drive adapter based on my motor shaft coupler. I used a 3/8" NPT pipe nipple, a left over 1/2" bolt and two 1/8" roll pins or spring pins (see my 3$ coupler article for details about the parts).

Use a 1/2" bit to drill out the 3/8" pipe (any 1/2" I.D. metal tube will work). Insert the threaded section of the 1/2" bolt (or any 1/2" O.D. rod) into the pipe and center it. Drill a 1/8" hole through the pipe and rod. Secure them together with a 1/8" roll pin. Drill a 1/8" hole about 3/8" in from the end of the pipe opposite from the rod (see pic). Drill through the first layer of the pipe and slide the pipe onto the pump shaft. Use the slot in the shaft as a guide for the bit as you drill through the back side of the pipe. The slot will ensure that you drill straight through the pipe. Insert the other roll pin in the hole you just drilled. Check the location of the pin by placing the pipe back over the pump shaft. The pin should slip into the slot on the shaft. If it doesn't line up, just tap the pin out of the pipe, rotate the pipe 1/4 turn and try again. The roll pins should fit tightly into the holes, but if they are not you can hold them in place with a few wraps of tape. Cut the head off of the bolt and you're done.

Now you have an adapter that can be secured into the chuck of any 1/2 drill without wobbling. The other end of the adapter will slip onto the shaft of your pump. If you only have one pump or just want to secure the adapter to the pump, you can pin it like you did with the bolt. I have a couple pumps so I like having the ability to quick change the drill to any pump.

I made a simple bracket to secure the drill to the pump with a piece of 3/8" threaded rod. You can use zip ties(cable ties/wire ties), a u-bolt, banding strap etc. to secure the threaded rod to the handle of your drill. Or just let the drill rotate until it hits the rod and stops. I have details and a pic on my blog.

You could use a lathe to turn down the 1/2" bolt or make something to shim a 3/8" rod into the 1/2 I.D. pipe. You can make a shim by threading a couple nuts on a bolt and grinding them down or just wrapping some good old duct tape around the bolt (but it might not last too long). The 3/8" bolt would allow you to use a drill with a 3/8" chuck to drive the pump.