Question regarding vacuum chucking

[govarney]

Gidday,

I am looking to use the builtin vacuum system that comes with my stubby. Problem is I've never used a vaccum chuck so I need some help.

I guess the main question is how much vacuum is required. Can I just connect a household vacuum cleaner or do I need something more powerful.

I been doing a bit of research and quite like the idea of a venturi type pump but alas has no idea whether it is suitable or not.

I've looked on a few woodworking shop websites and while a lot sell vacuum chucks/systems and haven't seen any that recommend a vacuum pump/system.

Any advice/help most appreciated.

[steck]

Hi,
I use a Vicmarc Vacuum chuck on my lathe with an old old vacuum cleaner and it works well.

[hughie]

Hmm dunno if a venturi would give enough and they can expensive to run. Vacuum cleaners work, bare in mind it might not have a extensive life. But still if you buy a a few second hand what the heck :U
I have a vane vacuum pump 240volt excellent for the the chuck, perhaps a bit dear for the average turner.

Perhaps look around for a second hand one, they are very easy to fix or rebuild.

[rsser]

I used a domestic vac on my Stubby; drilled 2x 1/8" holes in the cuff as some air has to come through to cool the motor.

[Texian]

Most folks in the U.S. apparently use the 1/4 hp. sliding vane pumps, probably like Hughie's. With the inlet blocked these will pull 25" hg or more, but these systems require a bleed valve to limit the vacuum applied to the work (like Ern's vent holes) to avoid collapsing the piece.

Any workpiece requires a certain clamping force holding it to the chuck, first to simply hold it there, and second to create sufficient friction between the work and the chuck to resist the force of the turning tool. This clamping force is the product of the pressure different between the inside and outside of the work (delta P) and the area (A) of the chuck. With a sufficiently large chuck, relatively little delta P is required, as might be supplied by a shop vac. With a small chuck, a large delta P is required, as might be supplied by a sliding vane pump pulling 20" hg vacuum. Beyond this the vacuum source must be capable of a flowrate equal or greater than any leakage in the system or through the workpiece, at the required vacuum. The shop vac would excel in flowrate capability, although it will not pull much of a vacuum.

Bottom line, shop vac will work on relatively light weight work pieces if a large enough chuck is used.

But you knew all that.

[turnerted]

I use an old vacuum cleaner on my homemade vacuum chuck .Remember to leave a centre mark on your tennon as it makes it much easier to centre your bowl on the chuck .

Ted

[Mulgabill]

Exactly as steck said. Not a problem even with larger bowls etc.

[TTIT]

Gidday,

I am looking to use the builtin vacuum system that comes with my stubby. Problem is I've never used a vaccum chuck so I need some help.

I guess the main question is how much vacuum is required. Can I just connect a household vacuum cleaner or do I need something more powerful.

I been doing a bit of research and quite like the idea of a venturi type pump but alas has no idea whether it is suitable or not.

I've looked on a few woodworking shop websites and while a lot sell vacuum chucks/systems and haven't seen any that recommend a vacuum pump/system.

Any advice/help most appreciated.I scored a small vac' pump for the right price from my SIL when he upgraded to bigger units (auto-sparky - uses them on air-cons) and hooked it up to the built in system on my Stubby. Running at about 20 to 25Hg holds just about anything and if you turn thin enough it will start pulling air right through the timber and let go (DAMHIKT :B ). Can't speak for the cleaner type vac's - never tried it :shrug:. Some basic shots of my setup on my website here (http://www.ttit.id.au/gadgets/gadgets.htm#Vacuum).
I've seen pumps like mine go for as little as $180 on Ebay but call your local auto-electrician and see if he's got any old rigs he's not using :;

[govarney]

Thanks for your advice guys. I ended buying one of those shed vacuum cleaners from Aldi's. A few parts from Bunnys and bingo I have a vacuum system. (I'll take a couple of photo today and post just in case someone else is interested).