Want to try vacuum clamping again...

[LazyMan]

I purchased a vacuum pod system a while ago but never got it to work properly for unknown reasons.

Anyways I am seeing some people make there own with success. I want to make my own but I have been scarred from my own experience and I have never seen one in real life. To me its almost a mysterious subject.tr I want to hold hard wood that would be 8x8 inches so I would have 64sq inches of area to work with.

I need to know if this can work, and work well. My machine feed rates would not be beyond 150 ipm and would be around 60 IPM for vcarving, and no deep passes. Is the wood going to move around and leave chatter marks? I have read through the threads here (particularly Greolt's,) and still cant seem to figure out what I need. I see talk about using a compressor to do this or converting a compressor to vacuum pump. How do you do this? I just do not know much about compressors and pneumatics. What CFM and pressure would I need? Anyone got recommendation for a compressor. Are there any smaller vacuum pumps for sale at a reasonable cost?

Some of this stuff may seem very basic to others but I am stumped on this vacuum clamping stuff. I am trying to create a production process and vacuum clamping would be ideal. I am willing to spend a good amount of money IF I know it will work.

[ger21]

This might help a little.

http://www.joewoodworker.com/veneeri...umclamping.htm

[LazyMan]

Thanks,

I have come across this site a few times but never realized they sold kits with a vacuum pump. I think I am going to get the Excel 5 vacuum press kit with the vacuum clamp kit. I will probably cut my own actual vacuum pod with a grid in it. Does anyone have any experience with it by any chance?

[BobF]

Atmospheric pressure is about 15 psi. With 64 square inches you could get 64 * 15 = 960 lbs of clamp force with a perfect vacuum. Ok, so you can't get a perfect vacuum, but some vacuum pumps can give 26 inches of mercury or so. Thats a lot of clamping force. Vacuum cleaners can't give anywhere near this force on a small area. If your seal is not good, your vacuum clamp won't be very good either.
surplus center used to have a good selection of pumps for a good price.

[LazyMan]

Well 900 lb wood be great but some how I doubt I would get even half that. Realistically how much force do you think you could get if you were trying to hold down a solid surfaced piece of maple wood for example?

[ger21]

Depends on the size, and how good the seal is. With a good seal, you should be able to get maybe 8-10 lbs/sq. in. Without a good seal, it could be much less.

I'd guess he's getting at least 300-400 lbs in this pic.
http://www.joewoodworker.com/veneeri...ping/idiot.jpg

[BobF]

With a good vacuum pump, you can get enough force to hold a bowl on a wood lathe with a vacuum clamp of 3" diameter and sometimes less.
Maple is fine grained not that porous. With a good seal I would bet the 10 lbs Gerry mentions is doable. That gives you 640 lbs.
On another site there are members making vacuum chucks from pumps like this.
https://www.surpluscenter.com/item.a...-1669&catname=

[Geof]

When machining plastic on a vaccuum platen I have found that it can be held down okay, i.e. it does not lift off during cutting, with a modest vacuum but sometimes it will slide because the vacuum clamping force is not enough to get a good frictional grip. Putting fixed stops around the perimeter to stop sliding can make a big difference.

[ger21]

www.allstaradhesives.com sells a stick on "friction tape" called Z Grabber to help prevent sliding. You use it inside your gasket around the perimeter of your part.

[Drassk]

You can get 27mm hg consistently on wooden pieces (ebony, mahogany, maple) so long as they're thick enough that the air doesn't suck right through the workpiece. On pieces thinner than 0.1" suck-through starts to become an issue.

If you stop the part from moving laterally, vacuum is enough for just about any sort of woodworking you can think of. Almost 100% of my fixturing here for guitar parts is vacuum.

[LazyMan]

Thanks guys!

Definitely going to use some type of sand paper type "friction tape."

[jdell42]

Does anyone have experience with this kit?

http://www.m-powertools.com/products...h/big-mach.htm