vacuum chucks

Re: vacuum chucks

Leo Van Der Loo

>Hi Dennis

That question is something like how much can I load on a vehicle ?

Answer, it depends.

Your vacuum question's answer is also, it depends on :

Size of turning, size of chuck, the turning's (bowl) length, balanced or not, RPM's, etc., the most important one though is the area of your chuck.

A more precise answer needs better input.

Have fun and take care

Leo V

Re: vacuum chucks

Fred in NC

>Dennis, all the answers to your questions came up very recently in this forum. I suggest you use the search facility at the top of the page, using just the word "vacuum" and you will have enough reading for a while.

The force holding a bowl against a vacuum chuck is proportional to the inches of vacuum AND the area (suface size) of the bowl. So it takes less vacuum to hold a larger bowl. The formulas have been posted recently as I said above.

Re: vacuum chucks

Peter Teubel

>Assuming light finishing cuts...

Depends on the size/weight of the piece. I've turned a 14" bowl with only 5"hg using a 6" vacuum chuck. On the other hand, I feel aprehensive if I have less than 20"hg holding a 6" bowl using a 3" vacuum chuck.

Re: vacuum chucks

Mark Kauder. Phenix City, AL

>An example of what the other guys are saying. I used a vacuum chuck to turn the ends of some small 1.5" diameter eggs - it was pulling at least 20" of vacuum an the hold was tenuous at best - you could pull the egg out with you hand.

On the other hand, yesterday I was turning the bottom of an 11" bowl, and at 6-7" of vacuum you could not budge it.

Mark

Re: vacuum chucks ???

Darryl Hansen

>Question not an answer. Isn't the holding power of a vacuum chuck driven by the area within the chuck that is at a vacuum? By that I mean you use a material between the chuck face around the circumference of the chuck and the item. The vacuum is drawn in the space inside the material. Isn't that the area that should be used to determine the holding power of the vacuum. If you have a bigger chuck and hence a bigger area within the walls of the padding material you will have more holding power. I don't believe it is the area of the bowl itself that maters is it?

Re: vacuum chucks ???

Jim Pugh, Ohio

>You are correct. It is the diameter of the chuck, actually, the point on the chuck that is in contact with the bowl/platter/other, that establishes what area the vacuum is working on.

I think that Area = pi x Diameter. In this case Diameter is not the outside diameter of the chuck but as mentioned above, the point at which the chuck surface is contacting the bowl. This can vary all over the place depending on the size of the bowl and whether you have the concave surface in contact with the chuck or the convex surface.

Another thing to keep in mind is that the strongest hold is within the diameter of the chuck. If you start working outside the chuck diameter, ie on the rim area of a larger bowl, you need to be very gentle with your touch. Even sanding too agressively can lever the piece loose from the chuck. Luckily it generally won't fly away, just relocates off center.

Re: vacuum chucks ???

John Lucas

>You are correct sir. you win the bonus round. I frequently use a 3" vacuum chuck to hold bigger bowls because I made this one 6" deep and it lets me reach way inside. I don't have a lot of holding power but then I always use the tailstock until the last possible moment.

Re: vacuum chucks ???

Fog Tanner

>its pi (3.1415965) times radius squared for area. Pi times diameter = circumferance.

Re: vacuum chucks ???

Dennis Bilevich PRESCOTT AZ

>Thank you all for the replies to my question regarding vacuum chucks. So I will assume that my vacuum pump that will pull 20" of mercury should be sufficent for any size chuck that I use.

Thanks,

Dennis

Re: vacuum chucks ???

Greg in Oshkosh

>The force holding the bowl on is equal to the area times the pressure. So the area is Pi*r*r and the pressure is 15lbs times the " of Hg divided by 30. A complete vacuum is 30"Hg.

Re: vacuum chucks *LINK*

bill noble

>the vacuum you need depends on the size of the item and the forces you will apply. you may find my article on the subject helpful, see either my web page (www.wbnoble.com_) or the tips section of www.woodturners.org. hope this helps


http://www.wbnoble.com