Jack Repair

I was doing some automotive work last weekend when the release mechanism on my jack broke.  I had jacked the car up and placed jack stands under it.  When I went to lower the jack, which requires twisting the handle, there was a little bit of resistance and then the handle spun freely.  Hmm, not good.  I used another jack to free my broke jack and was able to get the car safely back on jack stands.  I inspected my jack and found that the universal joint had broken.  My jack is an aluminum Craftsman jack and they felt like saving an ounce by making the U joint out of aluminum as well.  This doesn’t seem like the best decision in my mind.  Anyways, seen below is my broken universal joint.  The square end on the left fits inside of the jack handle and rotates the valve on the right side of the pic.  The U joint has two pins of different sizes and the body piece that the larger pin went through broke.  I looked online but Craftsman didn’t offer a replacement part that didn’t involve buying the cylinder.  Guess I’ll make a replacement part.

JR1

To start I chucked up a piece of 3/4″ steel rod into the lathe to drill a hole through it.  Before drilling, I used a center point to start the hole.

JR2

Next, I drilled to an appropriate depth with the lathe.

JR3

I cleaned up the surface with a few light cuts to eliminate the mill scale.  The original part was 3/4″ diameter.  So, my part will be a little smaller but made of a stronger material.

JR4

Here’s my piece once I’d parted it off the lathe.

JR5

From this point, making the part will require drilling three holes through the part.  Two holes are for pins and the other hole is to remove a large amount of material to form the U.  I used my height gauge (Thanks Gill!) and some Dykem to scribe the location of the holes.  I also used a small machinist square to scribe a vertical line to align the two pin holes.  Finally, I lightly punched the hole locations to keep my drill bit from wandering.

JR6

Here’s the point I’d use a mill…if I had one.  Since I don’t, it was off to the drill press that did a good job.  I oriented the part as best I could under the drill bit and proceeded to drill the two pin holes.  JR7

I rotated the pin 90 degrees and drilled out what would be the bottom of the U shape.  After drilling I noticed that this hole wasn’t exactly 90 deg from the two pin holes.  This was unfortunate, but not bad enough to trash the piece.

JR8

I held the piece in the vise and used a hack saw to remove the material between the large drilled hole and the end.  Then, I used a file to round over the edges and clean up the inside of the part so that the cross journal block would fit.

JR9

I dressed the ends of the pins I’d removed and then reassembled the universal joint with my arbor press.  Once I was satisfied with how everything fit I peened the ends of the pins to keep them in place.

JR10

I reinstalled the part back into the jack, bled it, and gave it a couple test releases.  Success!

JR11

Now back to putting the transmission back in the car.

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3 Responses to Jack Repair

  1. Gill McLane says:

    Extremely well done repair David. Next time bring it over to cut the middle part out on the bridgy. You should consider posting this write up (better yet a link to this blog) to the Home Shop Machinist forum. I think others would appreciate it also.
    Gill

    • davidjbod says:

      Thanks! I’d considered coming over to use your mill but don’t want to get into the habit of borrowing it every weekend! I still need to sign up for HSM.

      David

  2. Craig Aumack says:

    Please tell me you didn’t adjust either of the screws in the last photo….

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