Let's see your vacuum tables !

[cyclestart]

Up until now I've been holding down material with wood screws or 'fences' (trap the wood with other pieces of wood). A T-Slot table might be an improvement but you still have to mind the clamps.

Two questions:
For an 18"x18" area would a venturi design with a small air compressor work OK ?

The size of the vacuum chamber in the table, does size (volume) matter ? I'd like to cut the chamber(s) in a 1" thick sheet of material.

[ger21]

Two questions:
For an 18"x18" area would a venturi design with a small air compressor work OK ?

You'll need a perfect seal, or the part will never get sucked down. If you're cutting MDF, the vacuum will suck through the MDF. How fast it goes through, I'm not sure. I should probably make a small fixture and hhok up My venturi and see how it holds MDF.

The size of the vacuum chamber in the table, does size (volume) matter ? I'd like to cut the chamber(s) in a 1" thick sheet of material.

Not volume, but surface area inside the gasket seal. Vacuum holding force is measured per square inch. The more square inches, the better. With no leaks, and holding a non porous material, you can probably get about 10 lbs/in^2. So a 10"x10" table can get you up to 1000 lbs of force, provided there are no leaks.

[restless1]

smaller unit i am working on..

12X12" area

[cyclestart]

Wow, that's much prettier than any mechanical thing built in this shop

It looks like aluminum top and bottom. What was used as a gasket ? Were there pictures taken before assembly ?

I dismissed vacuum as too expensive before finding this cheap venturi system:
Project: V2 Vacuum Press - About the Project
It looks like it should work, if not for a whole table at least for a fixture.

ger21
I don't cut much mdf so far but tomorrow who knows.

[restless1]

i cannot take credit I purchased the table itself from here

Standard

mounted it to my aluminum table base can remove it when need be...
it came with gasket material for an overlay..

[SteveS]

Check out this build I posted some time ago. I used it for couple years with just a shop vac. As it worked out I just put sections of cut up bicycle inner tubes over any holes not covered by the wood be held down.

Once the shop-vac was on I could not physically move the wood.

http://www.cnczone.com/forums/cnc_wo...ble_build.html

A couple oops moments with the Z axis created slots that caused too much leakage. The design was suppose to have a sacrificial top board, but I got in a hurry. It lasted quite a while.

I have now gone to tabs or cutting to leave a skin. That works for most of what I do now. It is on the list to rebuild the vacuum though.

Steve.

[Phife]

I have the largest venturi Joewoodworker sells. Its not the best for vacuum hold down because i cannot flow enough CFM. I ended up using several vacuum pumps and they work much better.

Save your money and go the pump way, a compressor can work if you can reverse the reed valves. Otherwise it will work for a bit if you reverse the intake and exhaust but you will eventually bend the reed valves and it wont work again.

Vacuum pumps can be bought for $25-50 on ebay. Thomas brand vacuum pumps.

Look in the Hold down and Fixture forum for more info on vacuum tables.

[cyclestart]

Phife
I spot a fellow Canuck The shipping on those pumps is a big ouch unless the seller wants to work with a guy on the delivery details. My router is simple and cheap. I'm trying to stick with that theme btw I took a look at your machine and it's in a whole different class. Industrial grade.

SteveS
Now we're talking my budget What's the smallest piece (surface area) that system can hold down ? A downside is the shop vac runs full time, on the other hand the router is an ear plug zone in either case.