Puzzled by vacuum chucks

[Graham]

I know some of you here use them.

I have been watching some youtubes about building one that attaches to a shop vac and I am perplexed. I have a Camvac set up next to the lathe, if I cover the end so there is no air supply for it to suck then it will fairly quickly cave in the filter bags cage and presumably do an imitation of the fabled ouslum bird...... But blocking of the air supply is exactly what makes a vacuum chuck work so what gives

[Paul Hannaby]

The filter bag collapses because there isn't enough air flow to keep it inflated.

[john taylor]

MOst, if not all, systems that are designed to be run using a vacuum cleaner have some sort of bypass vale so that while keeping the vacuum at the chuck it will allow enough air through to keep the vacuum cleaner happy. 

From what others have said a Camvac or similar is not suitable for this sort of thinf and you will be much better off using an ordinary Vacuum cleaner.

Or the best way is to buy a vacuum pump, they can be had for about £150 upwards on Ebay and have a system which is designed for the job.

john

[Graham]

Hi John.
Is the problem with the Camvac the way the filters are designed ?

Any idea what size of vacuum pump would be needed ( i.e cubic feet per minute ) ?

[Paul Hannaby]

Somewhere around 8cfm would be ideal.

You might find this article useful.

[Graham]

That is a good article Paul, many thanks for the link.

[GwilymF]

I have a vacuum chuck set up using a household type vacuum cleaner and it works well. Most cleaners have a simple air release valve at the top end of the hose operated by thumb and this is what I use to control the amount of vacuum. It is essential that there is a flow of air or the vacuum cleaner will burn out.
Gwilym

[Graham]

I have had a look on a certain internet auction site for a vacuum pump but there are various types like refrigerant pumps etc. I have no clue about such things, is there a specific type of pump I need ?

[Andy Coates]

Try here:

http://www.bobchapman.co.uk/html/for_woodturners.html

[Les Symonds]

Try here:

http://www.bobchapman.co.uk/html/for_woodturners.html

....brilliant article, Andy. I've always looked upon them as being a bit too 'specialised', but this has changed my mind. Maybe I'll have a go at one of these, one day.

Les

[edbanger]

Hi Graham

I brought one of the units that work off the air compressor so I did not have to buy a pump and it works fine, I think that it was about 250.00

A couple of the members of our club came up with vacuum chucks at the last meeting, and one is very simple, a refrigerant pump we were told would suit the bill no problem so long as it can get up to the require pressure.

Follow this link to the clubs newsletters and look at the July one http://www.gardenofenglandwoodturners.org/club%20newsletters%20.html

Ed

[Graham]

Andy - Many thanks for the link. Bob has written an excellent series of articles.

Ed - Thats a really good club newsletter. And the info I needed, refrigerant, makes the choice a lot easier. Thank you.

[Turners cabin]

selfless plug but have you seen theses http://www.turnerscabin.co.uk/index.php?main_page=product_info&cPath=23_81&products_id=586

[Graham]

Thanks for the link but I think I will have to build my own