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Thread: Vacuum pumps

  1. #1
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    Vacuum pumps

    Rob Keeble asked me to say a few words about vacuum pumps and using them.

    There are several ways to generate a vacuum but I'm only going to discuss pumps. There are different kinds of pumps - some are designed for pulling a very deep vacuum, some are for medium vacuums, and some will pull a lot of air but not a very deep vacuum (e.g., a vacuum cleaner). For veneer work, you want a pump that will pull a medium vacuum.

    In the US, vacuum is often measured in inches of mercury, with 29 inches indicating a pretty compete vacuum (29.92). For veneer work, I usually use about 22 inchHg.

    To discuss volume of air: once you have the bag evacuated, you don't need a lot of volume. The reason for larger pumps (volume) is to get the bag pulled down quickly. If you have a pump with a 1/2 cu foot/minute capacity, it'll take a long time to pull the air out of the bag. You can use a vacuum cleaner to suck most of the air out, then switch hoses to your vacuum pump, but most people don't want to go through all that. They'd prefer to just hook up the pump and go. I find that a 3 cubic foot/minute pump works well.

    Continuous or intermittent pump? either works and the continuous is a bit less expensive. The advantage of the intermittent is the noise (it goes off), especially if you're working in the shop while pressing. Also, a very minor issue is that the intermittent pump may last a bit longer. My pumps are intermittent.

    Here's pictures of my pumps - I have two. The first is on a dolly because I teach veneering and take it to class. The second was installed in my shop to generate a vacuum manifold that I could tap into for veneering or vacuum chucking for turning. The kit for each came from Joe Woodworker. The pump for the smaller one came from Joe Woodworker and the larger pump I got on eBay.

    Questions?

    Mike
    Attached Thumbnails Attached Thumbnails Vacuum-pumps-001.jpg   Vacuum-pumps-002.jpg   Vacuum-pumps-003.jpg   Vacuum-pumps-004.jpg   Vacuum-pumps-005.jpg  

    Vacuum-pumps-006.jpg  
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  2. #2
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    Is a vac pump absolutely necessary when veneering ??? I'd like to give it a try but don't want to invest in any more tools that I may not use very often. (I don't believe I said that )
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  3. #3
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    Thanks for taking the time to post this. I would like to have a vacuum pump for two reasons. To stabilize punky wood for turning and for a vacuum chuck on my lathe. I think I read I need a medium size one(?). The darn things are expensive, least the ones I have seen. I've read where you can make one from something off of an old refrig. I've never found any plans or instructions. Is it a wise thing to do if I knew how to do it?
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  4. #4
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    What is the pvc chambers for?
    Are the gauges so you can regulate the amount of vac?
    Why would one want to regulate the amount of vac?
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  5. #5
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    Mike, I don't know much about vacuum pumps but I will say....WOW...you have a very clean shop floor!
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  6. #6
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    To add to Bob's question...I received some great 5x8 veneer and am interested in some 2-3 cigar humidors. Some of the veneer received is amazing!! At the same time, I just spent my billions on a grizzly sharpening system and a Jet 1642EVS. What would be a good wood to adhear this to given a spanish cedar lining...without a vacuum?
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  7. #7
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    Quote Originally Posted by Bob Gibson View Post
    Is a vac pump absolutely necessary when veneering ??? I'd like to give it a try but don't want to invest in any more tools that I may not use very often. (I don't believe I said that )
    There are other ways to press veneer. You could build two torsion boxes, or just use a couple of pieces of MDF and put cauls across them to get even clamping pressure. If you do much veneer work, you'll eventually get a vacuum system because it's much easier.

    If you use MDF make sure you use waxed paper or plastic between the MDF and your veneer so you don't glue the MDF to the veneer.

    Quote Originally Posted by Paul Douglass View Post
    Thanks for taking the time to post this. I would like to have a vacuum pump for two reasons. To stabilize punky wood for turning and for a vacuum chuck on my lathe. I think I read I need a medium size one(?). The darn things are expensive, least the ones I have seen. I've read where you can make one from something off of an old refrig. I've never found any plans or instructions. Is it a wise thing to do if I knew how to do it?
    You can use the compressor off a refrigerator but the volume is very low. It definitely would not work for vacuum chucking.

    Quote Originally Posted by Chuck Thoits View Post
    What is the pvc chambers for?
    Are the gauges so you can regulate the amount of vac?
    Why would one want to regulate the amount of vac?
    The PVC chambers are to store vacuum so the pump doesn't have to run so often. It works on the same principle as an air compressor. On an air compressor you have a tank (or a couple of tanks on the small compressors) that store compressed air. So when you use compressed air, the pump doesn't have to run right away.

    An intermittent vacuum pump works the same way. The tanks store vacuum and as the bag leaks, the tanks supply "vacuum" for a while which means the pump doesn't have to start so often.

    There's no advantage in having too much vacuum. If you pull excessive vacuum, your pump will run a lot more and wear out faster (and generate a lot of noise in the shop). As I mentioned earlier, I limit my vacuum to about 22 inchesHg and could probably use less. The gauges allow you to monitor how much vacuum you're pulling.

    Mike
    Last edited by Mike Henderson; 06-25-2011 at 03:25 AM.
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  8. #8
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    Both of those are nice-looking rigs, Mike. Mine is a continuous run setup. I'm only using it for vacuum chucking on the lathe, so it's typically only engaged for 5 to 10 minutes at a time. (I keep the tailstock in place as long as physically possible, so the actual vacuum time is usually pretty short.) If I ever start doing veneer work, I'll adding the tanks and controls so it can run intermittently.

    I didn't realize the Joe Woodworker plans provided for the continuous/intermittent switching capability. Is that essentially a backup in the event the vacuum-sensing regulator controls stop working?

    Quote Originally Posted by Chuck Thoits View Post
    ...Why would one want to regulate the amount of vac?
    In addition to what Mike mentioned, for turners it's useful to be able to dial back the vacuum a bit when using a vacuum chuck on thin or fragile pieces. It's pretty easy to suck the bottom off a bowl if it's thin.
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  9. #9
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    WOW Thanks Mike. I really did not expect a post so soon. Thank you very much.
    Could i ask you on the medium vac pump what exact pump make and model are you using ? This would provide some specific specs to reference to for a medium setup.
    I need to digest all you have said and come back with specifics.


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  10. #10
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    Quote Originally Posted by Vaughn McMillan View Post
    Both of those are nice-looking rigs, Mike. Mine is a continuous run setup. I'm only using it for vacuum chucking on the lathe, so it's typically only engaged for 5 to 10 minutes at a time. (I keep the tailstock in place as long as physically possible, so the actual vacuum time is usually pretty short.) If I ever start doing veneer work, I'll adding the tanks and controls so it can run intermittently.

    I didn't realize the Joe Woodworker plans provided for the continuous/intermittent switching capability. Is that essentially a backup in the event the vacuum-sensing regulator controls stop working?



    In addition to what Mike mentioned, for turners it's useful to be able to dial back the vacuum a bit when using a vacuum chuck on thin or fragile pieces. It's pretty easy to suck the bottom off a bowl if it's thin.
    Ah, I forgot about that switch. Thanks for reminding me, Vaughn. Yes, that's for when I use the rig for vacuum chucking. You can't have the pump turn off when vacuum chucking.

    It's just a modification to the wiring. You have a vacuum sensor in the wiring that turns the pump off when you reach a certain amount of vacuum. I just put a switch across the sensor which shorts it out when turned on, so the pump runs continuously.

    I'll expand on what Vaughn said about adjusting the vacuum for vacuum chucking, however. Since you run the pump continuously when vacuum chucking, you have to add a bleed valve that sucks some air. You adjust the bleed valve to adjust the amount of vacuum at the chuck.

    I don't do a lot of turning so I was answering the questions for veneering. Vacuum chucking is a special application and you need to do additional research before using a system for that. I'm not a good resource for information on that.

    Mike
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