Materials I purchased:
Hitch pin $2.00
Nylon washers $0.50 each
Used jack $10.00
All of the other items I had laying around my shop.
This is the floor jack I started with, sold under a number of brand names but they are all very similar. It's shortcoming is that it is so compact that it doesn't get under the car far enough.
First I removed this circlip and pin so that the head of the jack would flop forward and give me access to the circlip underneath (see next step)
Removing this circlip and short pin allowed me to separate the two circular pieces that make up the pad of the jack. The larger one is welded to the frame which is okay.
I bought a 1/2 inch diameter hitch pin with multiple holes pre-drilled in it to replace the short pin that originally went through the two circular pieces. I put a nylon washer under the head of the hitch pin and one where it passes through the circular piece, a cotter pin holds these in place. There is no load on the pin so a cotter pin is adequate.
This where I start to fabricate things. The aluminum plate is 1/4" thick and 2" X 3". The steel saddle is from a used jack purchased at a local auto recycler, it matches the saddle on my factory jack. The steel saddle has two 90 degree bends in it done with some heat and a vise. (apologies for not having a before photo of the saddle) Originally the parts of the saddle with the bolts through them would have been on the same plane as the sides of the saddle. I drilled 4 holes in the plate to match the holes in the saddle and tapped them M6x1.0 to accept the 4 socket capscrews and bolted it together. The large hole in the centre is 1/2 inch to fit over the hitch pin in the previous steps. On the underside I used my belt sander to make everything flush (pic 3)
I slid the fabricated saddle and aluminum plate over the hitch pin so it now rests on the large circular piece which is welded to the head of the jack, this will carry all of the load. A 3/32" hitch pin clip holds the saddle in place but everything can still rotate.
This the jack in use on my car at the factory jacking points. I swap my own summer and snow tires and this makes the job a breeze.
I also wanted to use the jack on my motorcycle for doing some work, the plate in the photo is another piece of 1/4" aluminum plate, 2" x 3" attached to a piece of 1/2" hardwood, maple is what I had on hand. The hitch pin was cut off so it is flush with the top of the aluminum/hardwood piece but is still long enough to allow the saddle to be attached. This piece allows me to jack up the bike under the engine to change a front tire or jack the rear tire and wheel assembly into place to allow me to line up the axle, brake caliper etc. and not struggle with the wheel assembly. As shown I can use it with the aluminum plate facing up, the hardwood is more than strong enough as long as I'm not lifting my car with it like this. This is my first Instructable and I hope my text and photos are clear and that someone may find this helpful.