Tool & Die Vacuum Question

"I'm trying to build a vacuum fixture for a sheet metal job. How much vacuum is needed to hold down a sheet 12.0x16.0x.032?"

You will need a welded steel box of 1/2" thick stock with the top surface-ground.

An area slightly smaller than the 12 x 16 work piece is drilled with a rectangular pattern of 1/8" holes on 1/8" c. to c. over the entire area into to vacuum chamber below. Use a Roots Blower as a vacuum pump. You are looking for a low gauge pressure, not a laboratory "high" vacuum.

The shop I was associated with part time had tried to use a large noisy vacuum cleaner and complained about the noise. The Roots Blower pulled a better vacuum and had the benefit of being much quieter.

Hold it down to do what? Is it steel, aluminum, SST? If you are machining aluminum an aluminum fixture with an "O" ring groove around the perimiter and a rectangular grid pattern will work just fine. The aluminum plate should be at least 3/4in thick. You can pipe tap the bottom of the fixture to attach your vaccuum hose.

Is it steel, sst, or aluminum? What are you going to do with it? Machine it? Most machine shope make vaccuum fixtures out of 3/4 to 1inch aluminum plate with an "O" ring groove around the perimiter and at the location of each hole. You cut a grid pattern for the vaccuum based on the shape of the part, drill and tap a hole in the bottom of the plate for a pipe fitting for your vaccuum hose and that is about it. An air pressure operated vaccuum pump is usually enough or a refridgeration pump is even better. If you are going to drill a lot of holes in the part vaccuum may not be the best answer, in which case there are other tooling setups that would work. I would have to see the part to advise.