Vacuum chuck relief valve

[Mike Vickery]

Alright one more vacuum chuck system question.
I read somewhere that it is better to use a needle valve than a ball valve for the relief valve.

I noticed that the needle valves cost quite a bit more. What are you guy's using and do you have any problems with it.

Not a 100% I am going to make the system, but am planning on running it by the wife this weekend. Don't mind spending a little more money but would hate to just waste money. From running some numbers these systems have a way of adding up.

[Jim Becker]

Your dealing with varying vacuum and the precise control you have with a needle valve vs a ball valve is significant.

[Bill Blasic]

Needle Valve will give you precise control.

[Richard Madison]

Mike (and others),
The uninitiated (and the ignorant) want to know, whatstheneddlevalvefor? Is it to limit the amount of vacuum applied to the workpiece in order to keep it from imploding? If so, how do you decide how much vacuum is enough?

[Mike Vickery]

Mike (and others),
The uninitiated (and the ignorant) want to know, whatstheneddlevalvefor? Is it to limit the amount of vacuum applied to the workpiece in order to keep it from imploding? If so, how do you decide how much vacuum is enough?

Yes it is to adjust the amount of vacuum so you do not implode as well as to allow just a small amount of vacuum so you can center the piece before you turn the vaccum up to actually turn.

From what I have read most turn at around 16 to 18 on the vacuum, but since I do not own a system yet this is just hear say. I think a lot of it is guess work and common sense. Lower vacuum on really thin pieces, more on very heavy solid pieces. But like I said I am just guesing so maybe someone that actually uses one will chime in.

[Dario Octaviano]

Mike,

If you do proceed with yours, please share where you bought your components (esp the valve). You seem to (always) have the knack on finding great deals. ;)

I have most parts/components waiting to get assembled...can you tell I am procrastinating on this? :o

[Stuart Johnson]

I use a ball valve and do not have any problem. I don't see any need to pull an exact vacuum.

[Larry Marley]

I also use a ball valve without a problem, but now you have me thinking...

I use the ball valve for a quick vacuum release as well as the control for max vacuum on the work. I can see the value of having one valve for total vac and one for quick release for positioning so I can return to the same setting without readjusting as vacuum increases.
Does this make sense?

[Stuart Johnson]

Larry, I might be missing something but why are you concerned about returning to an exact vacuum? I use a low amount to adjust the bowl and when done turn it up to around 16 or so. If it is a real thin piece I'll use a a lower amount of vacuum and very light cuts.

[Larry Marley]

Stuart,
I am doing the same as you.
I only use the vacuum chuck to remove the tenon and finish the bottom. The interior is finished, making for a consistent seal from one bowl to another. If I did this I would just add a second ball valve as a pre set. I agree with you that it is unnecessary. I was just curious if anyone was doing it.

[Richard Madison]

Thanks, Mike. I didn't think about the need to apply just a little vacuum while centering the piece.

[Martin Braun]

To be honest, I don't even have a valve inline yet. I usually don't turn very thin bowls. If I do, they are usually small anyways, and can take higher vacuum. If one has a big, thin bowl, then I would definitely think a valve would be useful. I guess if I needed to vacuum chuck a hollow form, then maybe it would be handy. Maybe what I'm trying to say, is that for most utilitarian pieces, it may not be a big deal.

[Randy Privett]

I use a radiator petcock to regulate the vacuum, just watch the gage carefully.

Randy

[Alex Cam]

The only needs valves I can find have compression fittings on both ends (ala Lowes/Home Depot). Can anyone point me to a source for where they got their threaded valves?

Thanks.

[Mike Vickery]

The only needs valves I can find have compression fittings on both ends (ala Lowes/Home Depot). Can anyone point me to a source for where they got their threaded valves?

Thanks.
I ended up getting mine at the same plave I got my pump.
http://www.surpluscenter.com/sort.asp?UID=2007082812441314&catname=misc&byKeyword=yes&search=needle%20valve

Enco I know also has them.

[Christopher K. Hartley]

I don't use a needle valve and have no problems at all. For the life of me I can't understand the need to be that precise. Mike gave you a great source for all the parts you'll need.:)