Vacuum chuck build

[olaf Vogel]

I've wanted a vacuum chuck system for a long time, but was impeded because the spindle on my lathe did not have a through hole. Well, now it does! Yay.

And last week I was innocently perusing Kijiji, when I came across a refrigeration manufacturer that is blowing out their old vacuum pumps. I picked up an Edwards RV8 for, reconditioned, for $100, including hoses and an air oil separator.



(BTW - they have a few more skids of these. If anyone is interested, I'll point you there - no affiliation)

So, I read through carious posts and articles, and am making my showing list of missing parts.
Here's how I "think" it will go together. Please let me know if any improvements are suggested.



The pump will go in the attic, along with the filter(s) and will vent outside.

Air filter - It seems I can use a normal pneumatic air filter, with vacuum, instead of pressure.
Supplied hoses are all quick connect. So I might have Princess Auto make up the remaining, in similar fashion.
Bleed valve will likely be a 1/2" ball valve - I've seen posts where the valve was too small to lower the pressure sufficiently.

Air reservoir tank. Some designs, like Joe Woodworker, has a tank inline, so the pump does not need to run continuously. And I would have to add vacuum switch(es) to turn the pump on/off. Is that advisable? It would be a Phase 2 requirement.

I'm very open to suggestions about alternative solutions.

Thanks

 

[Dwight R Rutherford]

I’d suggest an air filter at the bleeder valve as it will be partially open to regulate the pressure. This will eliminate contamination from dusty shop air being sucked into the pump.

 

[Tom Gall]

Air filter - It seems I can use a normal pneumatic air filter, with vacuum, instead of pressure.

Yes, they will work fine. However, I would check your vacuum reading (gauge) with and without the filter. I helped a friend set up his system and the filter he purchased offered to much resistance and reduced the vacuum considerably. Worked better after buying a different filter. My filter is installed right before/at the pump.

Bleed valve will likely be a 1/2" ball valve - I've seen posts where the valve was too small to lower the pressure sufficiently.

I just use my ball valve for temporarily shutting off / turning on the vacuum (pump remains on). I find that the ball valve is too difficult to adjust as a "bleed" valve. I have a little rotary valve (0º- 90º open/closed) which is very easy to dial in the amount of bleed you need. Don't know what it is called or if they are even available anymore. Any cheap air regulator can be used to dial in the vacuum you need.....not quite as quick or convenient but works well.....just disregard the pressure gauge.

I don't know about your pump but many pumps are continuous duty and can run for long periods. I've had occasions in the past where my pump would run for 3-4 hours at a time without shutting it off. Unless your electrical power goes out frequently you probably don't need a reservoir tank.

My set-up has the pump about 20-25 ft. from my lathe (original pump was very noisy...new one is quiet), but all the "controls" are right next to my headstock. This set-up has worked very well since I re-configured it when I got my "new" lathe (1996).

I'll try to include a scan (drawing) ..... no promises!!!

 

[olaf Vogel]

Dwight - good point about where to put the filter. I got the flow direction wrong on my diagram, at the valve part.

the filter he purchased offered to much resistance and reduced the vacuum considerably. Worked better after buying a different filter. My filter is installed right before/at the pump.

OK - I'll test the filters and see.

I just use my ball valve for temporarily shutting off / turning on the vacuum (pump remains on). I find that the ball valve is too difficult to adjust as a "bleed" valve.
View attachment 28384

So a valve like this?
I remember using that to adjust the vacuum on my old 1990's Celica, so that I could fool the ECU and increase the boost on the turbo.
They can be very accurate. But one post suggested the flow rates wasn't enough. I guess a bit of trial and error will tell.


Thanks for the feedback!

 

[JeffSmith]

Olaf - I realize this is a little late, but you didn’t need to drill your spindle - Vicmark have an adapter that doesn’t require a thru-hole. Its a nicely made unit. A friend bought one a few years back. Works fine.
As for your system - it looks like it should work well. I’m using a gast pump (bought for a song as retired, unused stock from a surplus outfit disposing of hospital surplus - $85) housed on the cart my grinder is mounted on in a filtered compartment away from the grinder down low. The manifold with supply hose, vacuum gauge and bleed valve are mounted on a magnetic base that sits on the headstock ready for use when needed, but out of the way. Power switch is on a pendant that stays on the side of the ways. Works great, and it is relatively unintrusive.
An air filter at the inlet of the pump seems to work fine - haven’t put one on the bleeder valve - seems like overkill to me. The element in the one at the pump has only needed changing a couple of times in the last 6 or 7 years....

 

[Karl Loeblein]

Tom, I'm still in the planning stages so I've got a few questions about your diagram:

• What is the purpose for the compressor line?
• Has there been any problems using an air hose for vacuum lines? Is your air hose the stiff plastic kind (vice rubber)?
• What size lines and hardware did you go with (i.e. 1/4 or 3/8)?
• Is the regulator and filters made from a vacuum or compressor system, or do they work with either?

Thanks,
Karl

 

[Tom Gall]

So a valve like this?

That might work...I assume the size is actually smaller than the picture. You may have to block off one of the openings (horizontal) if it allows too much venting. The only down side might be the barbed fittings which means you would have to add a piece of hose which would add length and flexibility .....possible resulting in a two-handed operation (no biggie I guess!). I prefer a direct attachment with a 1/4" NPT fitting.

Mine is only about 2" long (guessing!) with a small rotary, unmarked wheel that goes from fully closed to fully open every 90º in any direction. On my mini-lathe setup I just used a cheap air pressure regulator....rotate the knob to adjust the amount of bleed. I rotated the pressure gauge 180º so I don't have to look at it!

 

[Tom Gall]

What is the purpose for the compressor line?

Karl, the compressor line is totally unnecessary for most applications.....in fact, I may be the only guy that has one!!! I did shows for 23 years thru 2006, and used vacuum chucking on almost every item I made (some totally made using vacuum). Many items were semi-production type (batches of 10-20 at a time) and I was always in a hurry with the process. A few of the items required sealing an interior (unseen) surface and then reverse mounting (usually before the shellac sealer was cured) to seal the exterior surface. Most times the vacuum chuck would stick to the uncured surface and couldn't be removed easily without fingerprints on the newly sealed surface. Open the ball valve partially to the compressor and "Pop"...off it comes! It also works great for cleaning dust out of your spindle!!! Just be sure to turn off the ball valve to your vacuum pump before opening the compressor valve! DAMHIKT.

Has there been any problems using an air hose for vacuum lines? Is your air hose the stiff plastic kind (vice rubber)?

No problems for 25 years. I used HD rubber hose because that is what I had. Any length is fine you don't have to shorten your hose(s). I don't believe the stiff plastic kind was available back then.

What size lines and hardware did you go with (i.e. 1/4 or 3/8)?

I have 3/8" ID hose. Larger ID would work but is much more $$$ and isn't necessary ... the 3/8" works just fine. I wouldn't use 1/4" ID hose. All the hardware (tees, couplers, elbows, barb and/or air fittings and quick-connects [not necessary but convenient], ball valves, etc.) are 1/4" NPT. My 3/8" hose had 1/4" NPT fittings.

Is the regulator and filters made from a vacuum or compressor system, or do they work with either?

They will (should) work with either. However, you must have a vacuum gauge! Not necessary, but I have two....a larger dial (4") mounted on the pump 20-25 ft. away and in clear sight (used as a reference) and a normal size (2-1/2" ?) mounted near the headstock. These can be used to troubleshoot any vacuum problems with the workpiece but, as said before, is not really necessary. Good luck when setting up your system!

 

[hockenbery]

Open the ball valve partially to the compressor and "Pop"...off it comes! It also works great for cleaning dust out of your spindle!!!

Hmmm?
I use vacuum to hollow balls. Always try the vacuum chuck nearest the diameter of the ball for maximum hold.
Sometimes I add foam to make a too large chuck work. At least three times the chuck and I had a disagreement in size the Chuck was right and the ball got pulled into the chuck. One came out easily the other two wedged the extra foam in against the walls of the chuck.

Compressed air would be an an answer

 

[Tom Gall]

Compressed air would be an an answer

Yes it would. I've had that happen as well...also with some ornament globes and other small bowl/vessel type objects that I mounted for repairs that were too close to the diameter of the chuck. If it is only for occasional use you could just adapt a rubber fitting and an air gun to the hand wheel side. Of course it would have to be held with one hand so you can catch your sphere with the other!

 

[hockenbery]

Of course it would have to be held with one hand so you can catch your sphere with the other!

With enough air pressure we could outdo the potato canons

 

[Bill Boehme]

For the bleed valve I recommend using a needle valve ... it will give you much better control on adjusting the vacuum level compared to a ball valve. It only takes a tiny amount of bleed air to make a big change in the vacuum level. I agree with Dwight's suggestion to put a filter ahead of the bleed valve to keep dusty shop air out of the vacuum system. Also, don't have the bleed valve too close to the vacuum gauge or else you will get a reading that isn't representative of the actual vacuum at the chuck.

Wood is surprisingly porous and a lot of dust will pass right through it so place the filter close to the rotary coupler. Also place the vacuum gauge close to the rotary coupler ... on the clean side of the filter.

You can use any kind of hose that won't collapse under vacuum so air compressor hose should work fine. A hose that is flexible is better than a stiff hose, but any hose that won't collapse under vacuum is going to be somewhat stiff. I used clear vinyl water hose with an ID of about ⅜", but if I were to do it again, I think that I would just go with plain black rubber hose. When designing your system be sure to consider pressure (vacuum) loss as a function of flow rate and hose ID. Keep the distance between the pump and chuck as short as you can. When I originally built my system I used air hose quick disconnect couplings not thinking about the pressure loss through them. As a result of being enlightened by John Giem's article on designing a vacuum system in American Woodturner a few years ago I got rid of the quick disconnects and went with plumbing fittings ... not nearly as convenient, but less lossy when you're trying to eke out all the vacuum you can get.

I don't see any reason to put the pump in the attic. Most vacuum pumps are so quiet that you can barely hear them and the extra hose length just means more $$ and more pressure loss.

Personally, I think that a reservoir is just wasted expense, but if it gives you a warm fuzzy then go for it. It won't hurt anything, but it's a place where water could collect.

 

[Dwight R Rutherford]

Here is a handy chart I use to gauge holding power. It also gives me an idea of how too much suction may be exerted on thin walled items to avoide implosion.

 

[Karl Loeblein]

...I have 3/8" ID hose. Larger ID would work but is much more $$$ and isn't necessary ... the 3/8" works just fine. I wouldn't use 1/4" ID hose. All the hardware (tees, couplers, elbows, barb and/or air fittings and quick-connects [not necessary but convenient], ball valves, etc.) are 1/4" NPT. My 3/8" hose had 1/4" NPT fittings.

... I used clear vinyl water hose with an ID of about ⅜", but if I were to do it again, I think that I would just go with plain black rubber hose....

Tom, Bill, Would you also go with 3/8" fittings wherever possible (i.e. needle valves, filters, pipe connectors, etc...) to keep from reducing 3/8" hose line down to 1/4" in order to avoid any pressure drops? for example, a 3/8" brass needle valve can be found on fleebay cost $13 so it's not more than 1/4" need valve. Why then use 1/4" stuff?​

 

[Bill Boehme]

Tom, Bill, Would you also go with 3/8" fittings wherever possible (i.e. needle valves, filters, pipe connectors, etc...) to keep from reducing 3/8" hose line down to 1/4" in order to avoid any pressure drops? for example, a 3/8" brass needle valve can be found on fleebay cost $13 so it's not more than 1/4" need valve. Why then use 1/4" stuff?​

I think that ¼" hose is just fine if you don't plan on having any unplanned events and everything goes as planned. Probably the most likely unplanned event is lots of air leakage including air that goes through and/or around the rim of the bowl while deciding that tailstock pressure isn't really necessary.

Several years ago my pump had an unanticipated thermal shut down. It took at least a half hour before the motor had cooled enough to restart. It was startling, but everything turned out OK because the tailstock was holding the bowl against the chuck.

Cost would be the only concern about the needle valve since it is only partially opened if at all.

I forgot to mention earlier that I installed a brass T on my Gast pump vacuum port and then put ball valves on the other two legs. One ball valve opens to atmospheric pressure and the other valve connects to the hose that goes to the rest of the system. The reason for this configuration is that my Gast dry rotary vane pump requires a shut down sequence that includes running the pump for several minutes with an open vacuum port, then blocked port, and finally open port. I think that the newer Gast dry rotary vane pumps do not require this elaborate shut down procedure.

 

[olaf Vogel]

So summarizing the comments above, I've made a few changes in my plans as follows:

- it came with about 20 feet of 1/2" industrial tubing, so I'll use that
- use a needle valve
- two air filters (they're only $15 each)
- a 3" gauge near the lathe for adjustment. Ideally another small one next to the pump

The pump in the attic, since most of my mechanicals are there, and I want the space downstairs.

I'd don't really understand the need to keep the hose lengths short. For my compressor, I've run up to 800' of hose, with no noticeable pressure loss. Is that different for vacuum?

Bill, you mention vacuum loss. Assuming the system doesn't leak, the only loss should come from the porous nature of the wood. IF thats that the case, then a larger ID hose should not matter. Am I missing something?

I'd like to keep on quick disconnect, at the lathe. Otherwise all connections will be permanent.

As for shut down processes - the manual recommends closing the value, before shutting down, to keep the oil from being contaminated.
But, if there are two filters before the pump? And this pump came with a huge oil reservoir (it was used professionally in a refrigeration shop)

 

[Larry Copas]

A ball valve right at the adapter makes it so easy to to position the work. I used this one from McMaster Carr.

https://www.mcmaster.com/4757k52



I also plumbed in a reserve tank because I use my pump with a bag for veneer work. Almost instant vacuum which is also nice on the lathe at times.

 

[Bill Boehme]

I would put one air filter close to the rotary adapter and the vacuum gauge right next to it. The other air filter should be on the atmosphere side of the needle valve and not as you have it illustrated ... in other words, you want clean air passing through the needle valve. It would be best if there were several feet of hose between the vacuum gauge and the needle valve to get a more accurate reading . You really don't need the gauge at the pump especially if it is only visible from the attic. If you want to know the vacuum at the pump, you can close the needle valve and plug the line to the rotary adapter. If you want to do a system leak test, you could install a ball valve at the pump, close the needle valve, and plug the line to the rotary adapter. With the pump running, close the ball valve and then see how long it takes for the vacuum to bleed down. There probably will be a slow leak at the quick disconnects and at the air filter.

Bill, you mention vacuum loss. Assuming the system doesn't leak, the only loss should come from the porous nature of the wood. IF thats that the case, then a larger ID hose should not matter. Am I missing something?

Think of water flowing through a pipe. There is a loss of pressure that is a function of the diameter of the pipe and the flow rate. If the flow rate is very low then there won't be much pressure loss. If the pipe diameter is very large then there won't be much pressure loss. With a vacuum system the situation is similar. But, there's a couple pump performance parameters that haven't been mentioned yet, but are more significant with respect to pressure drop:

• Blocked port vacuum -- this is the vacuum with zero flow.
• Open port flow rate -- this is the total airflow when the vacuum port is completely open to the environment and the vacuum is zero.

If you plot vacuum vs. flow rate it is essentially a straight line between these two data points. For example, my pump has a blocked port vacuum of 26 inHg and an open port flow rate of 4.5 CFM. If I can only get 13 inHg then I know that the total leakage is 2.25 CFM.

 

[Dwight R Rutherford]

Here’s my set up, pretty simple. Note the filter at the bleed valve.

 

[William Rogers]

My system is also simple. I use a Thomas pump. I have three of them where two are used to aerate my lake rebuilding one while one is in service. Those pumps run 24/7/365 and go about two years before I rebuild. I use one for my lathe. 98% of the time I want a full vacuum, just when setting up or if i have a thin turning do I want less. I have a ball valve and works just fine bleeding off vacuum. A needle valve would be more precise, but I'm not looking to make real fine adjustments. I have one gauge that i can easily see near the pump. With these pumps you do need a liquid filled gauge because of needle bounce. I use a inline gas filter and the clear reinforced tubing. I have a remote switch I can set on my headstock.

 

[Tom Gall]

Tom, Bill, Would you also go with 3/8" fittings wherever possible (i.e. needle valves, filters, pipe connectors, etc...) to keep from reducing 3/8" hose line down to 1/4" in order to avoid any pressure drops? for example, a 3/8" brass needle valve can be found on fleebay cost $13 so it's not more than 1/4" need valve. Why then use 1/4" stuff?

Karl, I don't think going larger is necessary....but definitely more expensive! Any 3/8" hose I've ever found has 1/4"NPT fittings. Even if you wanted to retrofit the hose to 3/8" fittings I don't think you can find a fitting (i.e. a barbed fitting) that will fit the ID of the hose. If you step up to a 1/2" hose they have 1/2"NPT fittings (???) and then you can go with all 1/2" or step down to 3/8"....at a much higher cost! All the 1/4" NPT brass fittings (tees, elbows, ball valves, etc.) can be found locally at most hardware/ big box stores at reasonable prices. Larger sizes are more difficult to source and will probably cost 50-100% more. As stated before, I've been using my system for 25 years and it meets all my expectations.

Re: your concern about pressure (vacuum) drop would be negligible if any at all. Also, you can use any length of hose (even coiled up to get out of your way).....think of it as a mini-reservoir tank! I would guess that the difference between a 25' hose (what I use) and a 50' or 100' would only take 1-2 seconds longer to come up to full vacuum. The only vacuum drop would occur if you had a power outage! Only happened to me once....but the lathe shut off....the vacuum lasted a few seconds before dropping the workpiece....and I was standing in the dark in my basement shop!

If you can't find a suitable "bleed" valve (or air regulator) locally here's a link to one for $6. You can remove the gauge and plug the port if it bothers you....or just turn it around.

https://www.surpluscenter.com/Air-P...1-4-NPT-Mini-Air-Regulator-w-Gauge-4-1780.axd

 

[olaf Vogel]

Thanks for the feedback guys. I did a bit more research.

Here's the article by John Giem that Bill referenced.

Interesting reading. The key point IMO, is that total leakage of the system must be less than the pump can handle. And enough flow in the pipes.
Which I interpret as: with a big pump, you can get away with a lot. Maybe that accounts for the variety of solutions.

In my case, the pump is rated at:
5.9 cu ft / min
Ultimate pressure: 2 x 10-3 mbar / 1.5 x 10-3 Torr (which I don't know how to convert)

Re: quick disconnects. Mine came with them, and the fridge shop needed the lowest absolute vacuum. It seems there are QD's specifically for vacuum:
https://www.torrtech.com/Pages/QDs1.htm
I personally have no experience though. I'll likely put one QD at the headstock so the barb can stay in the spindle.

Bill, I understand your point about pressure loss vs pipe diameter. But I assume that effect is the highest at the chuck.
I.e a 4" ID chuck will have a much lower pressure than in the pipe. And once the system is down to the desired vacuum, I assume the flow rate is lowest.
So as long as there is sufficient flow in the pipe (and pump capacity), then I would assume that's all that matters.

 

[Bill Boehme]

?... I don't think going larger is necessary....but definitely more expensive! Any 3/8" hose I've ever found has 1/4"NPT fittings. Even if you wanted to retrofit the hose to 3/8" fittings I don't think you can find a fitting (i.e. a barbed fitting) that will fit the ID of the hose. If you step up to a 1/2" hose they have 1/2"NPT fittings (???) and then you can go with all 1/2" or step down to 3/8"....at a much higher cost! All the 1/4" NPT brass fittings (tees, elbows, ball valves, etc.) can be found locally at most hardware/ big box stores at reasonable prices. Larger sizes are more difficult to source and will probably cost 50-100% more. As stated before, I've been using my system for 25 years and it meets all my expectations.

The numerical size of NPT fittings (¼, ⅜, ½, etc) seems to have little to do (more like nothing to do) with the actual size in inches until you get to pipe sizes of 14 inches and larger. In actuality, ¼ NPT couplings are probably the exact right size for 3/8" ID rubber air hose ... at least that is the lesson that I learned many years ago when I bought a bunch of ⅜ NPT air hose quick disconnect couplers. When I received them I was stunned because they were huge compared to what I was expecting. That was about forty years ago and since then I've tried to give them away to friends and relatives, but nobody will take them once they discover how big they are. So they are permanent residents in my rollaround tool chest.

 

[Tom Albrecht]

So what is the most commonly available filter?
Is a filter necessary if there is one built into the pump, like a Gast?

 

[Timothy White]

The numerical size of NPT fittings (¼, ⅜, ½, etc) seems to have little to do (more like nothing to do) with the actual size in inches until you get to pipe sizes of 14 inches and larger. In actuality, ¼ NPT couplings are probably the exact right size for 3/8" ID rubber air hose ... at least that is the lesson that I learned many years ago when I bought a bunch of ⅜ NPT air hose quick disconnect couplers. When I received them I was stunned because they were huge compared to what I was expecting. That was about forty years ago and since then I've tried to give them away to friends and relatives, but nobody will take them once they discover how big they are. So they are permanent residents in my rollaround tool chest.

Bill:
NPT and PIPE measurements are ID (inside diameter) schedule is wall thickness. Tubing measurements are usually OD measurements in smaller tubing. Pipe sizes are consistent across the board no mater the material they are made of. Tubing can be ordered with specific OD and ID. For example 6”OD 4”ID. Pipe size is defined by its ID no mater the material it is made from. Air hose clear tubing copper tube aluminum tube etc. ad nausium. Are generally identified by their OD.
this has been a major point of confusion for me for a long time.

 

[Bill Boehme]

So what is the most commonly available filter?
Is a filter necessary if there is one built into the pump, like a Gast?

The cotton felt filter inside the Gast rotary vane vacuum pump is there to catch large things that might get sucked in and damage the Kevlar™ vanes or aluminum housing. They are way too porous to catch fine wood dust. The filter that I use is the same as I use with my air compressor. I have a 5 micron cartridge in my filter, but I suppose that a 40 micron element might be acceptable. Wood dust is abrasive so we should do what we can to keep it out of the pump.

 

[Joseph Maiorano]

I may be a little late to the party......

Carl Ford has a good article on vacuum chucks. You can find it here http://www.carlford.us/pages/jigs_tools/jigs_tools.html just scroll down to vacuum chucks.

Hope this helps.