DIY vacuum chuck questions

[Pete Staehling]

I have tinkered with making a couple vacuum chucks, but so far have not found them to hold well enough in their current configuration and with my shop vac. I have not yet set up the lamp all thread and actually put a vacuum on the chucks when on the lathe. Trying them directly on the shop vac hose has not made the set up look promising enough for me to proceed as is.

They hold fairly loosely and do not seem like they will stay centered well. I tend to think maybe the problem is the poor vacuum of the shop vac. Am I kidding myself on that? I am willing to buy a real vacuum pump or improvise one from a refrigerator compressor, but would hate to go through the trouble or expense to have the chucks not work well any way.

It seems like they would work fine as long as I used a live center along with them, but at that point i don't see much or any advantage over a jam chuck.

Comments or suggestions?

[Paul Williams]

I recently made a vacuum chuck. My connection seals with O-rings on the inside of the spindle shaft and with a flat foam against the handwheel. I purchased the cheapest/smallest Harbor Freight vacuum pump. This of course requires filtering the oil from the exhaust or piping it outside. The pump will not stay ahead of even the smallest leak, but after achieving good seals on the spindle connection and all of the pipe joints it holds very securely.

I have no information regarding using the shop vac, but I would start by making sure you have zero leaks in your plumbing and a good seal to your bowl. Also some woods are porous enough that your vacuum source may not be able to stay ahead. As a test, I would coat a test piece with any good film finish and then try to hold it.

Good luck, building the system was fun and using it is better than all of the jam chucks and other methods I used before.

[Brice Rogers]

With a perfect vacuum (around 29.5" of mercury), you will have about 14.7# of force per square inch pushing on your work piece. But I suspect that with a shop vacuum you might only pull less than 5" of mercury. So you have roughly 2.5# of force per square inch. If your vacuum head has 5 square inches, then there is only going to be ~ 12 pounds force total. Not enough - - as you found. For a practical system, you probably need to be pulling at least 15" of mercury.

Some suggestions: (1) get a real vacuum pump with a decent CFM (I'd guess that 3 CFM is minimum and is a lot more than a common refrigerator pump can do), (2) get a vacuum gauge so you can figure out the vacuum and track down things that are leaking and (3) make sure that your sealed bearings are doing the job they are supposed to do. Some "sealed" bearings are of the non-contact variety and are essential not fully sealed. That is, they leak like a sieve. Shielded bearings are even worse. I recently learned that a person can buy oil seals that could be used with garden variety bearings.

After a bunch of disappointing results, I went to frugalvacuumchuck dot com and I ended up buying both a vacuum pump and a pair of really good sealed bearings. It made a world of difference.

[Pete Staehling]

Thanks. Very helpful. I had been skeptical about the shop vac idea from the start, but have read where some folks said it worked well for them.

In my testing so far, at one point, I attached the 2-1/2" vac hose directly to the chuck (not on the lathe). In that mode I figure I surely had tons of flow to overcome any leaks, but not nearly enough vacuum. Maybe I'll have to spring for a real vacuum pump with enough CFM.

I'll keep the bearing seals in mind as I proceed and replace bearings or add seals as needed.

[Jeffrey J Smith]

Using a shop vac for vaccuum chucking is/was pretty common in Australia and New Zealand - you might check with them (there used to be a couple that monitored this forum). Raffan used one for quite a long time. That said, regardless of the vaccuum source, keeping leaks to a minimum is critical. The wood should always be the weakest link.
I live very close to sea level - within 20 feet or so, and have chased down any leaks in the system. With the Gast rotary vane pump and a JT Turning Tools adapter (came with my lathe), I can regularly peg the gauge when using this setup. Finishing the bottom of an alder bowl the other day, the pressure dropped to a little less than half on the gauge. Alder is a relatively soft wood with open pores. I could feel the vaccuum through the bottom. With a 4” chuck there was still plenty of hold to complete the bottom. The minute I started sanding, the dust sucked into the wood and brought the pressure up to near normal levels. It pays to have a filter in your system before the pump.
Just a note - the same system with the Thomas Reichle rocking piston type pump (I think this is the type of pump Frugal uses) brings about 80% of the pressure. I used this pump for years before finding a good deal on a Gast RV pump. The rocking piston is now used for a carving stand that uses the same chucks.
By the way, if you’re considering using a shop vac, you might want to plan on putting it outside. The 16 gallon Ridgid vac I’ve got seems to have plenty of pressure, but the noise will drive you out of the shop. The Gast is much easier to live with and the rocking piston is nearly silent by comparison.
I was soimpressed with the JT adapter, I bought their chuck adapter that uses 2” PVC pipe adapters (available in sizes up to 6”) for chucks. it works great and is easy to change from one size adapter to another when needed. Used to make wooden chucks, but these are so much more consistant and easier to use I haven’t used the wooden ones in several years.

[Brice Rogers]

Pete,
At some early point, you'll want to check your bearing seals. I bought sealed bearings from a reputable source and they leaked like a sieve. Now, when I check a bearing, I'll press it against my lips and use a finger to plug the center hole. If I can blow into it or suck through it, it is a leaker. If you have a high volume pump, perhaps it can overcome some of that.

I bought a Thomas pump from frugalvacuumchucks dot com and it was a fresh rebuild. When I got it, it could draw about 24 or 24.5 inches of Hg. Now that I've used it for about an hour it is drawing 25.5 to 26 inches of Hg. At my altitude the theoretical max vacuum is around 28" of Hg. (In Denver the max vacuum would be around 24" of Hg. ) So my "suction power" is around 12 or 13 psi. That is quite decent. When I multiply that times the square inches of my small vacuum seal that it about 65 pounds of force and with my larger vacuum seal it is around 130 pounds of force. So, I am very pleased with my vacuum pump.

The bearings from frugalvacuumchucks seem to be very good in sealing.

BTW, as Jeffrey mentioned, the porosity of the wood can be a factor in the amount of vacuum you can draw. One way around that is to seal the wood inside. Another way is to wrap some plastic film over the wood on the chuck. Sometimes even squirting with water can help.

[Pete Staehling]

The shop vac was, for me, just an experiment to try out the idea of vacuum chucks with minimal investment. My shop vac is crazy loud. No way to I want to use it on a regular basis other than for a proof of concept or trial.

[Thomas Canfield]

My location is about 1700' so vacuum is reduced a little on my Frugal Vac. I like the fact that it produces a small popping sound above 20" Hg vacuum and quite different below 15" Hg indicating a loss of vacuum from start and warning to back off and get ready. It has been a good warning indicator. The higher vacuum allows using a smaller diameter vacuum chuck to fit smaller pieces and still have a good hold. I can't imagine the diameter of chuck required to use with a shop vacuum on a bowl say 10" diameter. The good thing is being able to use the live center to make the vacuum chuck a jam chuck for all but the small center nub under the live center to give additional safety using the vacuum chuck.

[John K Jordan]

Joe Woodworker offers some vacuum pumps. I bought one and it works well.

https://www.veneersupplies.com/searc...acuum+pump+cfm

Much of his web site is focused on veneer and veneer pressing, but he also has good info on building a vacuum chuck system and offers all the pieces you would need. The parts I got were high quality. The bearings, for example, were well sealed.

https://www.joewoodworker.com/veneer...umchucking.htm

JKJ

[Pete Staehling]

Thanks again for all the info.

I did a bit more testing and decided that my current chucks will work well at least in the larger size. My little 6 gallon shop vac doesn't seem to have enough suction to work with the smaller chuck I made, but the bigger one shows promise. My hope is that with a better pump I will be able to use the smaller size too, but if not I can live with it.

I decided to just take the plunge and buy a pump from "The Frugal Vacuum Chuck". It is ordered so I plan to wait until it comes to go any further.

[Alex Zeller]

They do make air compressor style vacuum pumps. They use a venturi effect so there's no moving parts. The downside is that your compressor is running. But sawdust won't be an issue. They are kind of noisy like a blow gun and if you put it outside it'll draw in moisture from the air and freeze (acts just like the cooling coil in an air compressor).

[John K Jordan]

...venturi... They are kind of noisy like a blow gun.

The venturi vacuum generators must not all be created equal. A gentleman brought one to the club to demonstrate vacuum diffusing and it was very quiet. I could ask him for the brand and model if there is interest.

JKJ

[Pete Staehling]

No experience here, but I read that the venturi ones were fairly quiet other than the fact that the compressor will be running at least some of the time. I considered one, but decided against it.

[Alex Zeller]

The only style I've used was one for a 55 gallon drum vacuum cleaner. I wouldn't call it loud but it wasn't quiet like a vacuum pump. A paint gun isn't that loud so I can see how a small air powered vacuum pump may not be. Of course you still have the noise of the compressor if it's near by.

[Pete Staehling]

When I ordered the vacuum pump from "Frugal Vacuum Chuck", I didn't order tubing or anything else. Not sure if that was a mistake, but I am now looking at buying it locally. My plan is to duplicate what they picture as their kit on their site for the general setup. Barb fittings and ball valves seem to be generally available and I probably have some of that on hand, but I am unsure what tubing to use. Do I need to use something specifically designed for vacuum or will the clear vinyl reinforced hose that seems readily available work fine?

I am also assuming that 3/8" lamp all thread is the way to go from the bearing in the chuck to the hose where it exits the hand wheel.

Suggestions or comments?

Edit:
Just heard back... He has none of the "Good Used Pumps" and refunded my money. Some glitch on the site allowed me to order an out of stock item. I am deciding between ordering a rebuilt one and the super frugal kit. So some of the questions in this post may be moot.