looking at moving hardness tester with air, looking for input

preface, I tried to do a search and I found a bunch of too much not dealing with what I wanted.

I have a 4'X8' surface plate. I want to make a head board for it that would have doors that I can close to keep dust off my center gages, dhg's, etc. Without a good place to store/use my hardness tester I figured I'd put in on a plate I can float it in to its hole in the head board or out to use it. I'm guessing it weighs a little over 200 lbs. I have an air supply close I intend to use that is 1/4" line at 90psi.

Before I start drilling holes I figured I'd ask for guidance on how I should fix this problem I'm working on. I will use a pressure regulator to dial in just enough air pressure to safely move the hardness tester. I need to go out to the shop to double check the size of plate I will end up starting with. An estimate would be: I'll use a aluminum plate 1/2 or 3/4" thick and about 9"wide X 20" long. I'm pretty sure I have a plate that will work that is surface ground.

With all of the above info, I'm looking for advice/guidance/info on things I should and should not do making this plate.

Thanks in advance
Rosie

Rosie - Some automotive head machines use an air table to allow the head to be moved under the spindle to position the valve guides to be machined. One table I looked at was about 12 X 30, had only one air port directly in the center, and had two grooves in the underside crossing that hole at 90°. the 2 grooves were approximately .100" deep X .250" wide, and extended about 2/3 of the width and length of the table. Both the moving and stationary table were cast iron, not that that matters here.

PS - cool idea.

Mud
your input is precisely why I put this as a question. Some thing as simple a thru hole and a couple slots would be made so much quicker.
Thanks

If there are any Ideas better I'm still open to thoughts. This is on my list of "to do's" for early next week.

Rosie

Rosie,

You may want to consider another material besides aluminum for this job. Sliding aluminum around on a surface plate can make a mess, and its kind of difficult to clean off the smudges of aluminum too.

I understand that the idea is to float on a cushion of air, but there will likely be some sliding if you cut the air supply as you near your desired position on the surface plate.

You could put a layer of thin (.015) self adhesive UHMW on the bottom, cutting out around the air grooves. We do this same type of thing on some of the machines we build. We use large electromagnets to hold and position part of the machine. The magnet has lands milled in the bottom that we pressurize with air to float it into position. One thing to consider would be to have several evenly spaced, spotfaced "lands", and each one fed through an orifice. This will serve to ensure that the plate does not rock to one side, opening up a large gap, and allowing the air to freely escape. It will also help keep things quiet, as you really only need a tiny amount of air to float an object that is as light as that.

It is a very clever idea by the sounds of it, please post pictures when you build it.

Jon

Long ago I did something like this.
IIRC; the trick is to have a small orifice at each pad or foot. That way, as soon as it levitates, the pressure will drop, and maintain an air film. Each foot will reach it's own "perfect" pressure based on the air gap.

If you have a large feed tube to several feet, one will levitate, and drop the pressure. While all other feet remain in contact.

DJ

Proto,
I'm going to see what I have for plastic. I'm guessing I don't have a chunk big enough in house. I will shoot out a couple pics. My inspection room is almost clean enough to show, and I've been waiting to show off a little. The head board probably won't be built until late Feb or early March. I've got a lot on my plate right now.

Rosie