View Full Version : Vacuum Generator vs. Vacuum Pump Systems
Ned Ladner
I've read through numerous threads about vacuum chucking systems, including those operating with vacuum generators such as the Holdfast, and those powered by vacuum pumps such as those manufactured by Gast.
i would like to get the pros and cons of both systems based upon experience and, thoughts on how the two systems compare to each other as related to performance, reliability and cost.
Thanks in advance for your comments.
Josh Bowman
I have a gast pump and its upside is....uh........ well, it's not small, it's not quite, it is self contained, but I do like it. We use lots of venturis/air ejectors (vacuum generators) at work, they are noisy and hog air. I can't speak to the type that oneway sells, but it has to have some noise and has to have an air supply that meets its SCFM requirements. These vacuum generators can't produce the same total vacuum that a pump can, but really you only need 17" Hg to hold a piece of wood on a decent size chuck. Generally the venturis draw down faster than a pump, but only go so far. The nicest thing about the venturis is no moving parts! If you're starting new and have a decent air compressor, the verturi (vacuum generator) might be the way to go. I know John Keeton has one and seems to like it the last I heard.
Roger Chandler
I have the Holdfast as well........I like it because it was economical and it was ready to set up which was a simple process and came as a system.......I did not have to gather all the parts, assemble and hope for success.........the compressor I already had and that was a big consideration........
It does a good job and noise only comes from the compressor coming on and off.......which if you have a good sized one [mine is a 25 gallon, 5 hp.] then it is not too frequent.......every 10 or 15 minutes.....depending on the pourousness of the wood.......I have gotten 26 hg in vacuum on a few woods [denser ones].......most are around 18-22 hg .......adequate for my uses so far.
Jeffrey J Smith
I've got a Gast pump on my system, I find that it works great. My experience is a little different from what I've seen in some of the posts. I've got mine in a semi-enclosed section of the rolling cabinet that holds my grinder, and I can hardly hear it run. It draws down quickly and, with a good size chuck, can easily peg my gauge on the woods I normally turn.
The only drawback to a quiet pump is that, in the event that the thermocouple kicks in on a particularly hot day, without a reserve tank in the system, you can find your lathe turned into a launch site (don't ask how I discovered that). With either a generator or a pump, I'd recommend a reserve tank in the system.
Thom Sturgill
I started with a Holdfast on a Jet 1220. Did not like the through the head adapter and I was using a pancake compressor (all I has at the time) located in the lathe base. NOISY!!!
When I bought my Jet 1642 I had it in the back room of the rental house I was in - the small lathe was in my daughters garage across the street. I set up a vacuum pump and bought one of JTs adapters - much better than the through the head version. The dedicated pump (not a GAST) is small and quiet. I could run it without disturbing others in the house. Now I have a large shop and large compressor so the Holdfast with the better adapter would work fine, but I still use the small pump on the large lathe with the Holdfast dedicated to the small lathe. Maybe I'm just too lazy to reconfigure a working setup.
John Keeton
As Josh noted, I do have the Holdfast system and it does a great job. It is compact, simple, no maintenance, costs less than the pump system, and sets up quickly. I store it in a cabinet, though one could leave it in place. Personally, I don't like having extra "stuff" on the lathe all the time. I easily draw 23" on good wood. The Holdfast chucks do a good job, as well. However, unless they have redesigned them, you will want to "ease" the sharp edges on either side of the foam seal to avoid marking the piece.
Fred Belknap
John I was having the same problem with the hard plastic marking my turnings. I covered the foam rings in the vacuum chuck with some stick on foam from Walmart and it has worked fine. Mine will draw about the same as yours on good wood but most of the time a little less. I still use the tail stock as long as I can. I leave mine hooked up on the wall beside the lathe, it just takes a minute to attach to the lathe. I have used it a lot and it has done the job.
Jim Burr
I'm heading to the Holdfast...I'm not an engineer sopre-made is best! I've been using a refrigerator compressor picked up for $40.In my stabilizing tank, it pulls -28-30" mg...that discussion has alreadytaken place. I'm having a lash with that and a bleed valve to hold more in the15-20 range. It’s not fast, but neither am I!
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Sourcing a vacuum system should never be done on a whim. The investment not only has an initial purchase cost, but also an ongoing financial impact from operations and upkeep. When choosing among alternatives, you’ll find manufacturers of both Venturi vacuum systems and motor-driven (mechanical) vacuum pumps.
To get you familiar with your options, Venturi generator manufacturers include companies like Air-Vac Engineering, Gast, SMC Pneumatics, Thomas, and PIAB. While Becker, Busch, Travianni, G-D, Dekker, and Gast are examples of mechanical vacuum pump manufacturers.
No one benefits in the long run if you end up with a vacuum that isn’t right for your business, so take time before coming to a final decision.
Here are seven things to compare before purchasing a vacuum system.
OEMs often supply Venturi vacuum systems. And it may seem like a deal at first, as the upfront cost is less than a mechanical vacuum pump, saving you a small amount on the initial investment.
However, there are additional costs, such as maintenance, that come with a large air compressor. And more importantly, depending on the size and type of Venturi vacuum, the energy needed to run the supporting compressor is between eight and 17 times the required horsepower of a standalone mechanical pump.
For example, a Becker Model KVT 3.100 uses a 5 HP motor, whereas the comparable Venturi generator uses between 40 and 50 HP worth of compressed air. That’s eight times more electrical costs to run the Venturi than a mechanical vacuum pump!
Do you realize how huge that is?
Energy prices have risen year-over-year for more than a decade, and using a system that chugs electricity will, inevitably, get more costly as time goes on.
While the actual Venturi suction system has no moving parts, the compressor that runs it has plenty (significantly more than a mechanical pump). Of course, an increased load on the compressor will require more frequent maintenance procedures, meaning replacement of all those wear parts and increased oil changes.
If your in-house air compressor is close to using its full capacity, an additional compressor (and air dryer, filter, and regulator) will need to be purchased to satisfy the requirements of a Venturi. That is not an economical option.
While a mechanical vacuum pump generates heat, a Venturi’s compressor will generate about 8-10 times more, at 2,546 BTU/HP, because its motor is 8-10 times larger.
A Venturi generator needs to vent air, creating noise levels almost 16 times louder than a mechanical vacuum pump. Yes, a vacuum pump makes noise, too, but it can be remotely located if desired.
A Venturi vacuum system must have compressed air piped to it, which is extremely costly to install unless the machine is pneumatically operated and piping is already in place. A mechanical pump goes under or next to the equipment it supports, thus eliminating any piping needs.
If your shop air compressor fails for any reason, the primary source of your Venturi vacuum is out of commission. The resulting downtime will cost you in production loss and work hours. With a mechanical vacuum pump, you only need one backup pump for all of your machines to ensure uptime.
As you can see, a Venturi vacuum generator may sound good at first, but it will come back to bite you in the company wallet. Over time, mechanical vacuum pumps are more reliable and end up costing you less—so choose wisely.
Click the button below to see our selection of trusted Becker mechanical vacuum pumps.