Plumbing a Vacuum System for Your Wood Lathe: The Manifold

OK, you’ve purchased or built a vacuum pump for the vacuum chucking system on your wood lathe. Now you have to get the vacuum from the pump to the lathe and also control how much vacuum you need for each application. A few standard plumbing fittings and valve (or valves) combined with a few air line fittings, filter, a gauge and air hose, and you’re in business. One more thing — and this may sting a bit —  a rotating vacuum adapter for your lathe.

Basic components of vacuum sysem

Components of a vacuum system manifold are shown in the photo above from the left, rotating adapter, dust filter, inlet T with control valve and gauge.

Flexible hose

A regular air hose is suitable for any flexible hose in the system and as there is no significant flow of air, 1/4″ diameter is sufficient. A decent quality hose will resist collapse better than the very cheapest grade, so use mid-grade at least.

You will require something long enough to get from the pump to the manifold and a short piece from the manifold to the rotating adapter on the outboard end of the spindle. Friction loss shouldn’t be an issue in a length up to 20 feet, so it’s possible to locate the pump away from the lathe to reduce the noise and keep dust and shavings off the pump. Because the manifold is right at the lathe, the short flex line from manifold to adapter can be less than 2 feet.

Because you are using air hose it goes without saying that by using the quick connect fittings that go along with it where necessary will make life easy when setting up and breaking down the system.

Manifold

The manifold is an array of components that allow you to control the vacuum at the lathe.

For stability and easy access, it is handy to mount the manifold to the lathe itself. I welded a bracket on the piping, but there are ready-made brackets available that will do the same job. The size of the piping is best determined by the size of the accessories (valve, filter, gauge) again, because the flow is almost nil size is not an issue. The piping in the photo is 3/8″ black iron, though 1/2″ copper pipe would be fine if you’re more comfortable with that.

The line from the pump attaches to the manifold, which has a valve in-line for controlling the amount of vacuum as required. My personal choice is a quarter-turn ball valve because they have a very positive seal. In the photo below you can also see the gauge (barely) and in-line filter. More about both of those later.

Often a second valve is placed in the manifold to dump the vacuum to remove a piece from the chuck. I have found this to be unnecessary since there is usually enough leakage in the piece to draw the vacuum down all by itself — it just takes a few more seconds after closing the vacuum valve.

If you choose to install a vacuum dump valve, it can be installed with a tee anywhere on the manifold, venting to atmosphere. Alternately, to control the vacuum level you can use one valve but vent it to atmosphere, basically providing a controlled leak. If you’ve gone to the trouble of making a pump with a tank and vacuum switch, you have just made all the extras on the pump a waste of time and money.

Vacuum manifold

Gauge and filter

The gauge, though not absolutely necessary, is a very wise addition so that you will be aware of any leaks and in the case of delicate pieces, that you don’t apply too much vacuum. It must be an actual vacuum gauge, readily available at many hardware or automotive stores. Cheaper ones will read counterclockwise, but they are fine.

Vacuum reading after taping end grain

My filter is a cheap moisture trap adapted to vacuum rather than pressure, available where air equipment is sold. Typically these moisture traps have a gland type valve on the bottom to manually drain water from the bowl but only seal under pressure (and conversely, leak under vacuum). Simply remove this flexible rubber valve and replace it with some type of plug from the outside. I used one of the red plugs that covered the threaded fittings on the trap for shipping as seen in the photo on the below (cover removed). The filter simply allows dust and shavings to drop out of the flow into the bowl and settle in the bottom: nothing fancy.

filer with cover removed

You can see from the photo below that it is effective in keeping these gritty bits from making their way to the pump. By the way, almost all the shavings come from the hollow spindle, so if you blow that out prior to installing the rotating adapter you will reduce the problem immensely — I always forget.

Dust from filter

Rotating adapter

The rotating adapter is worth purchasing rather than making your own. I built my first one, and after some welding, careful turning on the metal lathe, buying two sealed bearings and carefully modifying an air fitting, it still leaked like a sieve. Bite the bullet and buy a rotating adapter. Mine is from Oneway and they sell adapters to fit all thread sizes, left and right. This will probably be the most expensive part of your system and will be about $100.

I made a mount to hold the adapter when not in use (pipe at bottom of headstock) and it is very handy. Alternately, you can install a quick connect fitting at either end of the hose. I was out of quick connects but did have a short piece of stainless pipe.

Alternate view of manifold and rotating adapter

The complete package

The yellow air line in the photos is the line to the pump. It T’s into the vertical pipe nipple just below the control valve — notice the pipe is plugged at the lower end where my original pump was plumbed into the manifold. It then T’s to the gauge on one side and through the filter to the rotating adapter on the other. Because virtually every piece put in the chuck leaks a certain amount of air, the level of vacuum is controlled by limiting the outgoing flow to the pump.

As you can see there is nothing complicated about the manifold. As my kids say, “Easy peezy, lemon squeezy.” There is no requirement for placement of components other than what makes the system handy to your own use. Keep it compact, sturdy and oriented so that it’s simple and ready to use.

On deck

The final chapter of this series will cover making the chucks themselves. If you’ve kept up with this so far, you will have no trouble completing your vacuum chucking system.

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