Vacuum Chuck

[cypher]

I have seen many homemade vacuum chucks using shop vacs and others usine vacuum pumps. I have some plans that i want to modify to fit on my lathe but my question is . . I have seen some vacuum pumps on e-bay and other sites and i am curious how many CFM are required to safely vacuum chuck bowls? I know it will depend on the size of the bowl but an average range would be nice. I am trying to decide if is worth buying a pump of just simply making one using my shop vac. Any help would be appericated.

[Gil Jones]

I think much will depend on your system leakage.
I watched a 4cfm, 1/4hp, Gast vacuum pump do a find job in a vacuum chuck system. I am going to use an old refrigerator Freon compressor, and see how that works before I invest in a pump.

[JackoH]

I use an old household vacuum clesaner with few prioblems, on a chuck designed by, and bought from Vic Wood several years ago. If the bowl is not to stable, support it with the live centre in the tail stock 'til the last minute then either turn off the remaining stub verrry carefully or remove and sand by hand.

[rsser]

Same as JackOh.

You need a bit of leakage (or bleed) or else you can burn out your shop vac. In my case, 850w vac and two holes in the cuff at the headstock end of about 1/8" each.

[hughie]

Cypher,

Its not so much about CFM as this refers to volume. Or how fast the pump can evacuate a given volume
But rather negative pressure ie -kpa 0-100 or inches of mercury Hg 0-32''. You could have 100CFM -10kpa and it would be useless or 1CFM -90kpa and be really effective.
Most vac pumps are very expensive so running with Gils idea would make more sense in the short term.
For a simple 240v pump you easily spend around $900 to $1500 and it would be very ordinary and not to fancy on the quality $1500 and up would get you something more reliable. Not with standing garage sales and second hand machinery places. But take someone along who is familar with vac pumps or has a good mech. background.
hughie

[JackoH]

Don't make it so bloody complicated.
Improvisation is much more fun!

[rsser]

Esp. when you lever the bowl off the faceplate right at the end of all your work (1x), or collapse the bowl with excess pressure (zero x, cross fingers). Or even better, turn off the vac forgetting to hold the bowl in place (1x, DOH!).