VACUUM CHUCK

There are times when you need to re-work a bowl after you thought it was finished.  A little touch-up sanding here, a little re-shaping there, fixing a ding somebody put in a piece at an Art Fair.  Or, you might just want a way to hold a piece while you turn off the bottom tennon so nobody knows how you had it attached to the lathe.  I find a vacuum chuck perfect for these applications. 

I've searched the Web and found all sorts of designs that used vacuum-cleaner motors, auto air conditioning compressors, venturi systems using shop air compressors to standard vacuum motor systems that cost upwards of $450.00.  I'm sure all of these systems work to some degree or they wouldn't be on the Web.   But, what I was looking for, was a first class system that had components that were designed and used for their intended purpose and didn't cost a fortune.  Below you'll find the plans for the one I built for around $150.00:

Let me just say at the outset, that this vacuum chuck was built for my lathe.  It may work on your lathe as is or it may require some modifications to suit your needs.

There are a number of major components in a vacuum chuck system.  First, there is the motor and vacuum pump. Second, a mechanism that allows a stationary air hose to be connected to a spinning headstock spindle.   Third, the connecting hoses, filters, gauges and valves to provide and regulate the vacuum realized at the workpiece.  And finally, the chuck itself to hold the workpiece. Sounds complicated but its really very simple.  I'll start at the motor/pump and work toward the chuck. 

MOTOR/PUMP

The motor/vacuum pump I bought was from Surplus Central (1-402-474-4055) (PO Box 82209, Lincoln, Nebraska  68501-2209).  The cost of the motor/pump was about $70.00.  You'll also need two starting capacitors, a vacuum gauge and a filter that fits on the input side of the pump (side towards the lathe).   These items are all available from Surplus Central.  The shipping took the standard UPS ground 5-7 days and the motor/pump came complete with a detailed wiring diagram.  What it didn't come with, was a mounting cradle for the motor (they probably had one but I didn't order it) so I built my own mounting base as you can see below.

I wired the capacitors as shown in the wiring diagram that came with the motor.  The wires are color coded and the process is straight-forward.  I also wired up an ON/OFF switch I purchased at a local hardware store.  Make sure the switch is rated for 120V and 10-15 Amps.  The box is a standard plastic electrical outlet box with a solid cover.  I drilled a hole in the cover to mount the switch.

FILTER, GAUGE, HOSE  AND CONNECTION FITTINGS

On the input side of the pump, I installed a 1 1/2-inch long nipple and a "T" fitting. A 90-degree elbow is attached to the "T" as well as another 1 1/2-inch nipple. The Gauge is attached to the elbow and the filter and a ball-valve shut-off is attached to the nipple as shown.  A standard male air hose connector is installed on the input side of the ball valve.

The hose that connects the pump to the lathe has a standard female air-hose connector at either end attached with small hose clamps. You can use any kind of hose you like but make sure the hose is heavy enough and will not collapse under a vacuum.  I used a reinforced clear plastic hose.  All of this hardware is available from your local hardware store or home improvement center.

HEADSTOCK SPINDLE ATTACHMENT UNIT

There's a gizmo you can buy from Packard Woodworking for about $50.00 that allows you to attach a vacuum hose to your headstock spindle.  I made an equivalent setup for about $10.00.  Again, All of these components are available from you local hardware store with the exception of the wooden piece (which you'll have to turn) and the sealed bearing.  I purchased the sealed bearing from a bearing distributor located in a town near me but I'm told there available from auto parts stores as well. 

The bearing size is not critical.  The only important dimension is the center opening.  This should be 1/2-inch to accommodate a 1/2 brass pipe threaded on one end that is press-fit into the bearing opening.  I had to sand the brass pipe a little to get it to fit properly.  You can use CA glue to seal the joint if necessary.

I turned a piece of 2-inch x 2-inch hardwood into a funnel shape, hollowed it out and drilled a hole in the small end to accommodate a threaded lamp rod.  The hole should be sized so that you can thread the rod into the hole. Once the rod is threaded into the hole, remove it and re-thread it with CA glue to seal the joint.  The length of this rod will have to be cut to fit your particular lathe spindle. 

The bearing I bought had an outside diameter of 1 1/4-inches so I turned a recess to press-fit the bearing in the large side of the funnel-shaped block of hardwood.

On the inboard side, I have a rubber grommet, washer and nut to fasten the rod/funnel block to the spindle as shown below.

Attached to the brass pipe that was pressed into the bearing, is a female-female-female "T" connector and a 90-degree elbow.  Next , I installed a bleeder-valve to "fine-tune" the amount of vacuum available at the workpiece onto one leg of the "T" connector.  This is used to adjust the vacuum so you can change the position of the workpiece on the chuck.  The 90-degree elbow is connected to the other leg of the "T", and finally, a short nipple and another air hose connector is installed.

The chuck shown below is a special chuck I made to finish the bottom on long-neck jars and vases such as the Hopi bowl (sixth in Segmented Gallery).  For general use, the chuck should be shorter but still have a cavity large enough to ensure sufficient vacuum applied to the workpiece.  The longer the chuck, the more vibration you'll have.  I recommend dedicating a faceplate to the chuck.  If you remove and replace the faceplate every time you use the chuck, it won't run true.

This particular chuck is made from cherry, 4-inch PVC drain pipe and some sticky-back closed-cell foam I got from an art supply store.  I turned a piece of cherry into a bowl shape with thick sides and a hole in the bottom for vacuum.   I then turned a rabbit for the PVC pipe.  I turned another piece of cherry with a rabbit for the other end of the PVC.  This second piece is rounded on the face and covered with the sticky-back foam.  The PVC pipe is  glued into the rabbits with CA glue.

For a standard chuck,  just turn the bowl shape as described above but instead of turning a rabbit, round it off and face it with the foam as shown below.  Here I've used laminated birch plywood (to build depth) instead of the cherry.  Also shown  is another chuck I use for finishing the tops or bottoms of box lids.  Like me, you'll probably make a number of chucks for different applications.