John's Power Steering Pump

John Zimmerman, along with his son Bob, is in the home stretch of a long restoration of his Buick Riviera, which he has owned since the mid-60's. A couple of weeks ago, it finally returned to Bob's shop with a show-quality paint job by Horsepower Enterprises in Lancaster.

Now for the "simple" task of putting it all back together! John asked my help with his power steering pump. The shaft was quite worn, and the pulley didn't fit right. Even a replacement pulley didn't fit well. My first attempt was to create a spacer with an internal taper to match the worn shaft, and that ended in failure and frustration.

Then, Bob realized they had a second pump from a parts car, and he was able to salvage a good, straight shaft from that. My task was to make a custom sleeve that married the 0.560" shaft with the 0.622" bore in the pulley. That means that the walls of the sleeve would only be around 0.030" inch - 30 thousandths.

I started by turning a brass rod to be a good slip fit in the pulley, and then drilled it to 1/2" - that's 0.500". After that, I used a tool called a boring bar to enlarge the hole to fit.

Measuring an inside diameter like that isn't the easiest thing, but fortunately I had borrowed a set of telescoping bore gauges from a friend at Make717. These clever devices (left photo) have "anvils" that are spring-loaded, and you slip it into the hole, and tighten a knob on the end to lock it in place (right photo). Upon removal, you can use a caliper or micrometer to measure the actual diameter.

It took a while, but eventually I had a good sliding fit on the shaft. Notice I tested it while the workpiece was still in the lathe, in case I needed to go farther.

I moved the work to a collet chuck in the milling machine, and milled a slot to allow clearance for the Woodruff key that secures the pulley.

I returned to the lathe to cut the sleeve to precise length, and with a little clean-up I had the finished piece:

It was a good fit in the pulley - you'll probably have to expand the picture to even see it in there:

And the shaft fits just right - success!

You can see in the photos - in the earlier failed attempt, the piece jammed and I chipped the paint on the pulley, which had just been professionally painted by Horsepower Enterprises. John is never going to let me forget that one!