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My Vacuum Chuck system

Raul McCai

Raul McCai

Joined
Oct 29, 2014
Messages
469
Likes
90
Location
nj
I've had this twin stage pump for a while. Got it free. Only recently decided to use it.

Here's the pump
https://photos.smugmug.com/Tools-I-made-or-Purchased/i-LSm2SS2/0/b6386067/1920/the pump vid-1920.mp4


The vacuum Rotary Union
https://photos.smugmug.com/Tools-I-...hLPB/0/c69641d8/1920/vacuum coupling-1920.mp4

More of the system connections and gauge etc., I take it up to 1241rpm no complaints
https://photos.smugmug.com/Tools-I-...s/0/8a354362/1920/vacuum at 1241 RPM-1920.mp4

First real use. Worked like a champ.
https://photos.smugmug.com/Tools-I-...0/bc476b23/1920/bowl on vac chuck-01-1920.mp4

I'm surprised at myself that I've never used this pump. I mean I was the Lab manager Engineer for a Ultra High Vacuum Physics Research lab for a university. There's not a lot about vacuum I don't know something about.
 
I am thankful every time I use mine that I have a vacuum setup. It is just about near the top of must haves for my turning.

By the way, I have never had a gauge for my system. I just adjust it until it cracks the wood and then back it off a touch. ;) Seriously, my turnings are not very thin to the point of too much vacuum, so I usually crank it to full pull. (Gast rotary vane pump) What is the advantage of a gauge? It’s not like there’s a formula for bowl size, bottom thickness, species porosity...
 
The biggest advantage of the gauge is to show you leaks. Some bowls leak and occasionally the system. It's nice to know that I actually have full pressure or whatever I need for that size turning.
 
Owen Lowe said:
What is the advantage of a gauge?
Click to expand...

When I am dialing the vacuum back the gauge lets me go to the pressure I want ( whatever that might be and for whatever reason) and then adjust the Parker Needle valve to hold that level of vac at a steady state. I suspect that this is not do-able absent a needle valve if for no other reason the smooth and delicate level of control a needle valve offers.

As to the notion of formula. Well there might be just that. The Youngs modulus for many woods is known (sort of - grains of salt needed cos each hunk of wood is different) and one can roughly calculate the fail point of a thickness of a generic lumber species against the PSI that the vacuum would be exerting across the square inches of surface area given any inches of Hg of pressure. That might inform one of what level of PSI one might want to avoid exerting on any given cross section of wood. I'd consider the thinnest point the weakest. Or, failing that, one could simply experiment with various thicknesses and stress them to failure. If one wanted a general guide one could just fail test a few sections of lumber and record the result.

One of these would be really handy http://www.metal-testers.com/produc...u6ySZRjkKug3lbHNc2nGq6Dl2BUljJ8saAoADEALw_wcB



I gotta agree with you The limited use I've made of my Vac Sysm thus far, the more I like it.
 
Last edited:
Raul McCai said:
I've had this twin stage pump for a while. Got it free. Only recently decided to use it.

Here's the pump
https://photos.smugmug.com/Tools-I-made-or-Purchased/i-LSm2SS2/0/b6386067/1920/the pump vid-1920.mp4


The vacuum Rotary Union
https://photos.smugmug.com/Tools-I-made-or-Purchased/i-HgWhLPB/0/c69641d8/1920/vacuum coupling-1920.mp4

More of the system connections and gauge etc., I take it up to 1241rpm no complaints
https://photos.smugmug.com/Tools-I-made-or-Purchased/i-MjS23fs/0/8a354362/1920/vacuum at 1241 RPM-1920.mp4

First real use. Worked like a champ.
https://photos.smugmug.com/Tools-I-made-or-Purchased/i-T5D7xkn/0/bc476b23/1920/bowl on vac chuck-01-1920.mp4

I'm surprised at myself that I've never used this pump. I mean I was the Lab manager Engineer for a Ultra High Vacuum Physics Research lab for a university. There's not a lot about vacuum I don't know something about.
Click to expand...

Wow! Noting your background as an engineer I can understand your penchant for overkill! Nice...and very serviceable but you could have saved yourself a lot of work.

A few recommendations: 1) You need a remote power switch at your fingertips (a simple fix with several options). 2) Add a ball valve to shut off the vacuum without turning off the pump. 3) Move your needle valve (or add a second smaller one) close to the headstock. Also, from the videos I can't tell how close your gauge is to the lathe. If you're like me, I probably wouldn't be able to see it well enough.

I have the power switch (remote), vacuum gauge, ball valve, and needle (relief) valve all within 12" of my headstock for easy reach. Also, in my set-up I use 2 gauges.....a larger one (4") located on/at the pump, but still in my visual range, and one at the headstock. My pump is about 20 feet from my lathe (for noise reduction....this may not be possible in every situation). Two gauges is helpful (but not really necessary) in determining any vacuum discrepancies. This has served me well for the past 24 years.

Raul, you're welcome to come for a play date....I live about an hour(+) south of you.
 
Tom Gall said:
Add a ball valve & remote switch
Click to expand...

Yah an extrea valve might be good. and a remote switch would save me a walk. I can release the vacuum with the needle valve. it's slow but slow is good. I won't drop work that way.

actually you are only about 43 minutes away.
 
Tom Gall said:
penchant for overkill!
Click to expand...

Don't say that to an engineer. That'll make 'em angry. Maybe you meant to use a phrase like "Industrial" or something like that?
My system isn't over built. Take the 1" hard pipe for exmple. Because I located the pump and reservoir a good long way away from the lathe, the 1" pipe is the absolute minimum pipe size that a wide range of life critical applications might require. 2" or 3" would have been better but I could not fit 2" behind my studs. Most folks would try to get away with hose or half inch pipe but 20 or so feet of hose or small pipe would get them hurt or even killed if they had a problem with a springing leak and a sizeable turning took off at 6 - 700 RPM heading for their skull. The small hose over that distance wouldn't move sufficient air to compensate. The turbulence in a small pipe is a serious limiting factor in any vac system. Ask an HVAC guy what turbulence does in a duct. One 90 degree bend is equal to an additional 20 feet of ducting. It adds up. Enough turbulence can reduce a powerful pump to almost nothing. I experienced this first hand over and over again in high torr vac systems and even on my Shop DC. I have a Felder RL 160. I wanted to build a little hand held sweeper. So I got a couple lengths of 3" Shop Vac ribbed hose and tried it out. The tiny 8 feet of hose and ribs created so much turbulence that my RL was unable to lift things off the floor. Switch to 4" smoother flex hose and all is better even with 20 feet of hose.
 
I thought a vacuum chuck mounted part constituted a closed system so the flow in the lines should be very low, unless the wood is very porous or an insufficient seal is made.
 
Raul McCai said:
Don't say that to an engineer. That'll make 'em angry. Maybe you meant to use a phrase like "Industrial" or something like that?
My system isn't over built. Take the 1" hard pipe for exmple. Because I located the pump and reservoir a good long way away from the lathe, the 1" pipe is the absolute minimum pipe size that a wide range of life critical applications might require. 2" or 3" would have been better but I could not fit 2" behind my studs. Most folks would try to get away with hose or half inch pipe but 20 or so feet of hose or small pipe would get them hurt or even killed if they had a problem with a springing leak and a sizeable turning took off at 6 - 700 RPM heading for their skull. The small hose over that distance wouldn't move sufficient air to compensate. The turbulence in a small pipe is a serious limiting factor in any vac system. Ask an HVAC guy what turbulence does in a duct. One 90 degree bend is equal to an additional 20 feet of ducting. It adds up. Enough turbulence can reduce a powerful pump to almost nothing. I experienced this first hand over and over again in high torr vac systems and even on my Shop DC. I have a Felder RL 160. I wanted to build a little hand held sweeper. So I got a couple lengths of 3" Shop Vac ribbed hose and tried it out. The tiny 8 feet of hose and ribs created so much turbulence that my RL was unable to lift things off the floor. Switch to 4" smoother flex hose and all is better even with 20 feet of hose.
Click to expand...

Raul, like I said ..... "overkill". "Life critical applications" ???.....probably not. But now that you've already gone through all that work & expense (copper pipe & soldering, etc.).....so be it, it's done and it's good! In my 24 years of vacuum chucking I only had one piece come off the lathe.....during a power outage! The lathe shut off and slowed down, the lights went out and left me standing in the dark in my basement shop.... making a "save" nearly impossible. The bowl merely dropped off the chuck, while the lathe was slowing down, and fell to the floor. This probably would not have been a problem for you as I see you have a sizable reservoir tank to give you a little more time. I didn't have one, and still don't, but had just enough suction to hold the piece on a little while longer while the lathe slowed down.

As I stated, my pump is at least 20' from my lathe. I use a good quality 3/8" ID air hose which works perfectly well. Any extra length will just act as a small reservoir. :rolleyes: The actual holding power comes at the chuck, the larger the diameter - the more air pressure/force applied to the piece (assuming you're not trying to hold a sponge :D ). Just like a compressor air hose....doesn't matter if you have a 20' hose or a 200' hose, the pressure at the nozzle is the same once the hose is filled with air (or vacuum).

I also have a homemade rotary union (two actually) that just just slides in or out of my spindle. One second to put it in....one second to pull it out. Quick change for use of other applications.
 
Raul McCai said:
Yah an extrea valve might be good. and a remote switch would save me a walk. I can release the vacuum with the needle valve. it's slow but slow is good. I won't drop work that way.

actually you are only about 43 minutes away.
Click to expand...
Raul- Where do you live? I'm on Wanaque, NJ. Its worth a trip down to Tom's shop. Its been years since I've been there, but Tom is very knowledgeable and willing to share/teach.
 
Bernie Hrytzak said:
I thought a vacuum chuck mounted part constituted a closed system so the flow in the lines should be very low,
Click to expand...

Yipper. But for those moments when it's not - and there are plenty of 'em. Well, small hoses and long small pipes will break your heart every time.
 
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