Vacuum Chuck

[bertterbo]

I'm thinking of purchasing a vacuum chuck setup. I currently don't have a compressor and have no real need for one, so instead of going the Venturi route, I plan on just getting a vacuum pump as they're much smaller and less noisy. I also have plans to do some wood stabilisation at some point, so that would be another use for a vacuum pump.

My planned parts are :

https://www.turners-retreat.co.uk/vacuum-adapter-kit/p156https://www.turners-retreat.co.uk/vacuum-hose/p395https://www.turners-retreat.co.uk/vacuum-head/p385
And then for the pump, which from my research, needs to be at least 3 CFM, I thought I would go with :

https://vacuumchambers.eu/en_US/p/Vacuum-pump-VP160,-170lmin-6CFM/24
Is this all going to be compatible? will I need anything else? I'm not sure what connections may also be needed?

 

[flh801978]

I have a vacuum setup on my graduate lathe which has a bearing on the outboard end with a large dia 15mm pipe to the pump
i have a bigger pump than that one you linked to when i use it ....but i have one of those too and i have used it to see if it works ( slower to come down to full vacuum)
your lathe has a hollow spindle?
The force on only a 100mm chuck is amazing you cant pull it off
i have 50,100,150 and 200mm chucks

 

[bertterbo]

I have a vacuum setup on my graduate lathe which has a bearing on the outboard end with a large dia 15mm pipe to the pump
i have a bigger pump than that one you linked to when i use it ....but i have one of those too and i have used it to see if it works ( slower to come down to full vacuum)
your lathe has a hollow spindle?
The force on only a 100mm chuck is amazing you cant pull it off
i have 50,100,150 and 200mm chucks

Yep, it has a hollow spindle. It's the Axminster 406 if it helps.

 

[Paul Hannaby]

I'm not sure if the pump spec is correct but it states the maximum vacuum is 5Pa. You would need a vacuum of at least 10"Hg which according to the internet is 33863Pa. That's a big difference to 5Pa...

Once you have all the equipment, you will also need a bleed valve to be able to control the vacuum and a vacuum gauge to tell you what vacuum you are pulling. You would also need the pipe work and probably a connector for the pump to be able to connect everything together.

One thing to watch out with the holdfast chucks is not to use too high a vacuum. If you do, the rubber seals compress to the point where the plastic body of the chuck creates indentations in your workpiece.

This might be of some use - Make your own vacuum chuck | Paul Hannaby Woodturning

 

[bertterbo]

I'm not sure if the pump spec is correct but it states the maximum vacuum is 5Pa. You would need a vacuum of at least 10"Hg which according to the internet is 33863Pa. That's a big difference to 5Pa...

Looks like it's measured in thousands, as other sites list it as "5Pa/0.05Mbar"

0.05Mbar == 5000 pascals

0.05Mbar == 1.47 inches of Mercury

So still pretty far off 10.

Are you sure it needs to be at least 10? Even the £300 vacuum pumps still say around the 5Pa mark? some even less.

 

[Paul Hannaby]

A total vacuum (at sea level) is 29.7"Hg. Most decent vacuum pumps will reach around 25"Hg. For a 6" chuck I adjust the bleed valve to give around 15"Hg. Using the graph in my article, 1.5"Hg would equate to only around 5lb holding force which is nowhere near enough.

 

[graduate_owner]

To flh801978.

Hi, I am thinking of making up a vacuum chuck for my graduate. Can you post (or email me) pictures and details of yours please, especially details and dimensions of the 'swivelling' bit? Many thanks, in anticipation.

K

 

[Yorkieguy]

Bob Chapman, who is a member of this forum (and West Riding Woodturners Group which meets at Bingley), was for many years a well-known and highly-regarded professional demonstrator on the 'club circuit' until he retired. Bob made his own vacuum chuck some years ago and provided details of how he went about it.

You might find these articles of help and interest:

www.bobchapman.co.uk/-1-_Making_a_vacuum_chuck.pdf

www.bobchapman.co.uk/-4-_Vac_chuck_modifications.pdf

About Bob:

www.bobchapman.co.uk/index.html

Bob's contact details on this forum:

Bob Chapman

Hope that might help.

Every success with your vacuum chuck project.

David.

 

[Bob Chapman]

Well, thank you David (Yorkieguy) for your compliments. Having seen Paul Hannaby's excellent contribution I didn't think mine could add much to what he'd already said, but it is nice to be remembered!
One thing I might add is that vacuum power is not well understood and, as both Paul and I point out, it is proportional to the area of the chuck. I once sold a perfectly good vacuum pump to a chap who contacted me a day or two later saying it was useless because it 'didn't suck'. Of course I gave him a refund and took the pump back. It still worked perfectly.
I suspect (but can't know for certain) that he'd switched it on and put his finger over the inlet pipe, experienced almost nothing and decided the pump didn't work. What he hadn't taken into account was the area of the inlet - a pipe perhaps 1/8 inch diameter or so. The vacuum pressure on such a small area would be tiny, just as he'd experienced. Connect it to a chuck with a diameter of, say, four inches and the power is enormous.
I only mention this because that initial 'put your finger over the inlet' is an obvious and compulsive thing to do, but beware your expectations - don't think you're going to feel much!

Bob

 

[bertterbo]

Well now I am a little confused.

This video shows him using a very cheap 3CFM pump that he says works fine.

Looks to be this one, which has no mention of Pa or HG. So can you can low CFM with high HG?
https://www.testequipmentdepot.com/.../vacumaster-single-stage-pump-3-cfm-15310.htm

 

[flh801978]

I have one of the little ones as well as a larger gast pump here’s the label and that will easily pull down to 15 inches
My gast pulls to 24

 

[flh801978]

This for GO is my connection for the outboard of a graduate

 

[flh801978]

So you have a LH threaded boss then a pair of 2RS sealed bearings a spigot glued into the bearings with loctite then a triple outlet connector with inlet pipe gauge and relief valve.
Ian

 

[Bob Chapman]

A high CFM number doesn't give you a better vacuum, it just does it quicker. A 3CFM pump will be fine. It shifts 3 cubic feet of air per minute. The total volume of your vac chuck system is a small fraction of a cubic foot. You'll achieve the necessary vacuum within seconds.

 

[Paul Hannaby]

Where higher cfm comes in to play is where the wood (which is often porous) is leaking air and reducing the vacuum. A higher cfm pump will maintain the vacuum better than one with a lower rating. Even with an 8 cfm pump, I still find occasionally I find pieces of wood which won't hold on the chuck due to the porosity of the wood. Sometimes that can be got around by covering the wood with clingfilm but that only works if you aren't trying to work on the area where the clingfilm is!

 

[bertterbo]

I think I am just going to go the Holdfast Vacuum Generator approach.

 

[Tris]

I'm just at the thinking stage of building a vacuum chuck set up having been given a pump and 6" diameter x 2½ft long piece of solid pvc to turn the chuck from.

My question is: how much effect does the depth of the chuck 'cup' have? I built a Longworth style chuck some years ago and had to use a spacer block on the faceplate to prevent it fouling the motor. The Jet 1442 has the motor in a most awkward place, so I wondered whether to make a deeper cup to allow clearance.

 

[flh801978]

These are my vac chucks
You can see the depth and the length of the fitting…biggest 200mm small 45mm

 

[Tris]

Thanks for posting those pics, looks like I can get enough depth to clear the motor with no problem then

 

[Lazurus]

I made my own set up to suit my VB36
https://www.ukworkshop.co.uk/threads/vb36-vacuum-chuck-and-rotary-adaptor.110814/