Sunday, September 12, 2010

A Floor Jack Hanger

I like tools to be hung up where I can see them, and get at them instantly. Rummaging about for things in drawers and cubbies is a nuisance, and the last time I had to retrieve my floor jack from its lair I decided that's about enough of that -- it's time to make this thing a hanger.

That steel strap will serve as material for the actual 'hook'. And since nothing goes to waste around here, I'll use that wretched chunk of 2"x 4" for part of it.

First thing to do is to saw that wood into a presentable rectangle, 1 1/16" thick. Resawing 'trash' wood like this often reveals some quite spectacular figuring. That chunk of wood was once part of a living tree, and I think you can really see that in this result:

So I have my neat rectangle, 1 1/16" x 3 1/4" x 5".

The steel strap is salvage. In a former life it was a shipping restraint for a Qume daisywheel printer . I have about a dozen of them, and I'm ever so glad I thought to snag them when I had the opportunity. They're very useful material.

They're galvanized mild steel 1 1/2" wide by 17 3/16" long overall. The length available between the two punched holes is 14 5/8". The thickness is 0.079" (about 5/64" or 2mm for all practical purposes). And stating a sheet metal thickness brings me to the subject of sheet metal gauge numbers. A wee digression is in order.

Sheet Metal Gauge Numbers

I dislike sheet metal gauge numbers for the simple reason that no one ever specifies which gauge they're referring to. There are at least four. There are six wire gauges that I know of.

Here's what "Machinery's Handbook, 21st Edition" has to say about gauge numbers:

"Much confusion has resulted from the use of gauge numbers, and in ordering materials it is preferable to give the exact dimensions in decimal fractions of an inch."

Amen to that. If I ever do state a gauge number in this blog, I'll specify which gauge I'm referring to, and I'll still include the actual thickness dimension.

With that out of the way, it's time to form a hook for the jack's 14mm diameter front axle to hang by. I've squared off one end of the steel strap to get rid of the portion with the punched hole. Now I have to rig a means of bending it into a hook shape. Here's what I came up with:

Crude and primitive, but it worked. (That 's 1/2" threaded rod.)

Two things about this setup were key to it succeeding:

a) The hardwood blocks for the c-clamp to seat on. The upper ends of the threaded rods had to be absolutely immobilized. The hardwood blocks made it possible to install the c-clamp squarely and securely.

b) A very firmly tightened vise. It's a good practice to periodically attend to a vise-screw's lubrication, especially at the 'head' of the screw where it bears on the front jaw. The force load at that point is enormous, and the bearing surface under the screw-head is relatively small. The screw-head needs to be well lubricated to rotate freely under load, and let you apply all the torque you can to good clamping effect.

If you look closely at the lower edge of the steel strap right at the front jaw of the vise, you can see that my forming job didn't come out dead straight. That was fairly easy to correct by clamping the short end of the hook in the vise and levering the long end to correct the flaw.

The rest of the job should be fairly straightforward -- cut the hook to a suitable length; lay out and drill screw holes as required; assemble and install.

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And voila, here's the jack hanging on the wall where I can get at it right quick:

The three screws attaching the hook to the wood block are N0. 12 x 1" pan head sheet metal screws. The two Tapcons are 1/4" x 1 3/4" hex heads. That's a very secure installation.

I counterbored for the Tapcons' heads because the 1 1/16" thickness of the wood block was too much for a 1 3/4" long Tapcon. Tapcons are supposed to achieve 1" of penetration into concrete for a correct installation.

If it looks to you like the Tapcons' heads aren't centred in their counterbores, it's because they're not. Getting holes drilled accurately placed in concrete is diabolically difficult. I had to drill 5/16" holes through the wood block to give me some adjustment latitude for plumbing the block, and it's still not perfect. That's the one flaw in this installation; otherwise I'm quite pleased with it.

I have the feeling, though, that I may have tempted fate here. The truck is liable to reward my work to make the jack readily accessible by coming up with a flat tire.

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It was really bugging me that I hadn't got this mounted perfectly plumb. I clamped a length of 1" x 2" hardwood to one side of it, parked a small level on its top surface, loosened it off, levered on it to 'adjust' it and tightened it back up. It's ok now. I feel much better.

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