Vacuum Chuck ?

Ned Bulken

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Lakeport NY and/or the nearest hotel
OK,
Stu's recent post of his Ginko bowl has me scratching my head.

I'm a Long way from needing one, but I sure would like to know How a vacuum chuck works. Obviously you apply vacuum to the plate and the workpiece is held on by the vacuum, there are vacuum router pads which allow clamp-less routing, but that I know of they have a constant source of vacuum. How the heck do you apply and keep vacuum on a bowl that is spinning at several hundred to several thousand RPM?
 
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................. How the heck do you apply and keep vacuum on a bowl that is spinning at several hundred to several thousand RPM?

Ah.......... carefully............ :D

basically the headstock in "most" lathes are drilled through for a knock out bar, to get things like your drive center out, so that becomes the pipe that the vacuum travels to the plate or vacuum chuck. The hose from the vacuum pump to this tube is usually attached via a bearing that fits into the handwheel on the lathe, there is a pipe or nipple in the middle of the bearing, this is where the hose attaches, the bearing spins, the nipple does not. Make sense yet :D :dunno:

Cheers!
 
Actually with my set up, I'm more worried about collapsing the bottom of the bowl, I think they call this "Funneling" it........ :doh:

Seriously, I know that the vacuum chuck is not as secure as say my Titan chuck with them spigot jaws on it, but there is a LOT of vacuum on the bowl.

Surface area of a sphere....
[FONT=Century Gothic, Arial, Helvetica]surface area = 4pr2[/FONT]

So if the bowl is a perfect sphere (and I know it is NOT) and 8" in diameter 4x3.14x4squared = 50.265 (about) so half of that for the half bowl is about 25 square inches of surface area, so if I'm pulling 20" of mercury........ ah.......:huh:

Dunno, would that be 20 x 25 500 pounds...?:huh:

Well, all I know is that it would take a REALLY huge catch to remove a bowl from my chuck, and as I'm just finishing off the bottom of the bowl, I don't think I have much too worry about........... unless I make the bottom to thin, thus "Funneling" it........... :doh:

Cheers!
 
Hey Ned, just wanted to show you, and everyone else, the neat factor on these vacuum chucks...........

little_hat_sucks.JPG little_hat_sucked2.JPG little_hat_sucked3.JPG


That is the little hat from one of my snowmen, I wanted to sand the underside of the hat a bit, and thought........"hey........ I got a vacuum chuck......" :D

and the next two pics, are a piece of hardwood, not light, is also held on the hat by vacuum, the wood that hat is made from is Hard Maple, not exactly porous wood, but there is enough vacuum there, through the wood, to hold that piece of wood on the hat, no rubber seal either.

LOVE this vacuum chuck! :wave:
 
Stu

If I recall correctly, you have a dedicated pump for that chuck, would a vacuum cleaner work? (maybe not as well?)

Jay
 
Sure Carol, it is just a piece of MDF, I think it is 21mm thick, with a thin piece, maybe 4mm, of semi soft foam on the face. I'm going to replace the semi soft foam with something a bit harder, this stuff is too soft.

Works like a charm, as you can see :D

I'd like to make some other chucks too, some bell shaped ones etc, but for now, this works well.

Cheers!
 
Yes Jay, I have a nice big vacuum pump, pulls lots of vacuum.

The vacuum adapter for the DVR is actually designed for use with a vacuum cleaner, or shop vac, but I tired it and it sucked only a little bit.....:rolleyes:
 
But the DVR vacuum attachment can take a pump as well.

So I guess if I'm going to go this way I get a "twofer" get a good pump and I'll be able to use it with a vacuum bag as well.

Lots more to learn!

Jay
 
Actually Jay, they say to NOT use a vacuum pump with their adapter, as it might suck the ball bearings and such out of it.

Oneway makes a good one, if this one fails, I'll be getting the Oneway unit.

Cheers!
 
A vacuum pump is next on my list. I have been eying em for about two months now and have bid a couple of times, even as recent as last night. I can't believe how lucky you were Stu to get that unit for the price you got it. I will probably get a smaller unit that runs about 200W (1/4hp).
 
Yeah, I know I was lucky, but I was looking for nearly a year, and I must have bid on at least a dozen or so desirable pumps, but got out bid. One reason I got mine at such a reasonable price, 11,800 yen, plus shipping, or about $100 US, is because of the size of this unit, it is easily 3 times the size and weight of most of the other pumps, so I do not think it is really "portable" :D IIRC it weighs in at 27 Kg, or about 60 lbs, overkill, you bet :thumb:

Cheers!
 
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