Vacuum chuck setup

Originally posted 9 July 2013

We had two demos at our woodturning club this past spring that involved vacuum pumps.  This wasn’t the first time that a vacuum pump had crossed my mind, so when a oil-less pump came up on eBay for a reasonable price, and withing driving distance of the house, I bought it. That was the easy part.

To use a vacuum pump, I needed vacuum chucks. To make vacuum chucks, I needed face plates. I decided to make my own from some nuts and washers ordered from McMaster-Carr, and Industrial Supply house that sells over the internet. The nuts are threaded to fit the 1-1/4x8tpi threads on the headstock spindle

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However, the nuts don’t thread right up on the shoulder of the spindle, and the threads need to be undercut on my metal lathe to allow them to do so.

Once side of the nut (shown above) is faced, and is pretty square to the threads, but the other side of the nut is not square. I also wanted to cut a pilot on the nut for the washer to fit over when I welded it, so it turns into several steps to do everything that I need to do to make the face plate.

I put the known square side toward the chuck and surface off the side with the numbers on it. Then flip the nut over and undercut the threads. Finally, flip the nut back over and cut a notch in the nut to pilot the washer.

Once all that is done, I welded the washer to the nut.

Next, turn the nut back over and cut a notch in the nut to pilot the washer.Once all that is done, I welded the washer to the nut.

I’m not proud of my welds here – after talking to a friend at work, I think I need a new liner in my MIG gun.

Back side – hard to see the curvature of the seam while welding – almost guess work.

After the welding was completed, I ground off the extra weld material from the back side of the washer so the wood will sit up tightly against it. Then I made a simple jig with a couple screws to keep the distance from the edge of the washer consistent and drilled and countersunk a hole off each point of the nut.

I had some mahogany that was given to me by a friend a couple years ago that I cut into rounds.  One of the pieces shown here was actually exchanged for a piece of maple that was large enough for a 6-inch(?) coupler. As shown above, I used the face plate that came with the Nova lathe for one of the chucks.

I screwed the wood to the face plate with hardened steel screws. I put  generous bead of sealant between the faceplate and the wood. I realized that I had not drilled a hole through the center of the wood, so I put it on the drill press  and drilled it out.  On the other one I drilled out the wood before I screwed it down, but I like this method better so will likely do future ones this way.

I then mounted the roughed out wood block for the chuck onto the lathe and…

… turned to shape.  I also opened up the hole in the center a bit.The next step was to cut a groove in the wood to insert a PVC pipe coupler.  The mahogany disk received a 3-inch coupler and the maple disk received a 4-inch coupler.

 

The 4-inch chuck above is shown with a walnut natural-edge bowl is shown mounted on the chuck, being used as a jam chuck with the tailstock holding the bowl in place on the chuck.

With the chucks completed, it was time to turn my attention to the rotary vacuum coupler. The vacuum needs to be transferred (for lack of a better word) from the pump to the lathe, through the headstock to the chuck. The spindle of the headstock turns so a coupler needs to be made so the vacuum transfers from the stationary to the rotating part of the system.  I used two sealed bearings for this that I bought off the internet from VBX Bearings (Google it).

I decided to make the coupler out of osage orange because it is a very stable and hard (dense) wood.

I drilled a 7/8-inch hole in the wood the depth of where I wanted the bearings to seat, then reversed the coupler in the chuck and drilled a 3/8-inch hole from the end into the bearing cavity.

I cut an o-ring groove around the end of the coupler and put a fat o-ring on it that I found at the hardware store.

I lose a little vacuum at the bearing end of the coupler, but there is very little loss of vacuum, if any, between the hole in the lathe end and the end of the spindle where the chuck screws onto the spindle.