This explains how to construct a duplicate of my shop built rotary vacuum adapter for using vacuum chucks on a lathe. Nearly everything is from the shelves at Lowe’s. The rod connecting the chuck and the rotary adapter is lamp rod, 30” long 1/8-ip threaded steel pipe, Angelo brand, part number 70270. Cut it to suitable length for your situation after finishing construction.

The rod screws into a brass fitting which is super glued into the ¾” thick MDF in each chuck. A suitable piece of hard wood could be substituted for the MDF. I have used Brass Reducer Bushings and lamp rod couplings for the threaded insert in a chuck body. Both seem to work well. The bushings will give an absolute air tight seal on the lamp rod but require a 3/8 pipe tap to install. They are located in the drawers of brass fittings in the plumbing aisle, and are part number A-776, 3/8-mip x 1/8-fip. You may find it easier to glue in a coupling from the electrical aisle. The part is Angelo brand, 70162 Coupling 1/8-ip thread. They will be in blister packs hanging near the lamp rod and there are two in a pack. Use thick super glue to bond it in a ½” diameter hole.

The rotary adapter is made from a 1” Adapter, Fem. Schedule 40, white PVC from the plumbing aisle. It is Lowe’s number 23864, and has 1” female threads in one end and 1” glue socket in the other end. You will drill out the glue socket using a Forstner drill bit of the same size as the o.d. of the bearing to make a tight fit on the bearing later.

The bearing is number 99502-H, .625 Bore, Double Seal for Ace Pump. It’s in the hardware aisle in the Specialty Fasteners drawers. I used one bearing in the first several rotary adapters I made, but decided to use two in this last one. I believe that two bearings are superior to one, but the adapters with one bearing have had no failures yet. Use a SMALL bead of super glue to bond the bearing to the 1” schedule 40 fitting you drilled out.

The bearing has a 5/8” bore and the lamp rod is approximately 3/8”. I used rubber “o” rings and rubber grommets to make up the difference and give me some shock absorption. The grommets are 5/8 x 3/8, Lowe’s number 139365, and are in the hardware aisle, specialty fasteners drawers, near where you found the bearings.

Lowe’s no longer carries the “o” rings needed for this project, but they can be found at Menard’s or Home Depot or your local Ace or other brand of Hardware Store. They are the standard #48 ring, size 5/8 x 3/8 x 1/8. For the single bearing installations I sandwiched the grommet between two “o” rings inside the bore of the bearing. For the double bearing installation I still used two rings and a grommet for each bearing, but I also added an extra “o” ring in the middle of the sandwich for a total of two grommets and five “o” rings.

All this rubber inside the bearings is squeezed together by two washers, one on each side of the stack up. The washers are 5/16 Bright Flat Washers, Lowe’s item number 63307, from the hardware aisle. You will need to enlarge and de-burr the hole in the washer to make it a close fit on the lamp rod. Drill it with a 25/64 twist drill and file off the burr on the backside.

Angelo Brand, 70621 Brass Lock Nuts, 1/8-ip thread supply the pressure on the washers. They can be found near the lamp rod display in the electrical aisle. I have always used two nuts jammed together with their flats aligned, on the open side of the bearing. This gives me a wider “nut” to put a wrench onto, if needed, when I am screwing the completed assembly into, or out of, a vacuum chuck. A drop of super glue between the nuts and on the threads of the lamp rod will insure that they stay put and act in unison in the future. The actual pressure on the washers is applied by tightening a lock nut inside the PVC fitting using a deep well socket.

After the nuts are tight, the outboard end of the PVC fitting is plugged with a 1” x ½” threaded bushing properly sealed with thread tape or thread compound. This bushing is white PVC schedule 40, and the Lowe’s number is 51323 in the plumbing aisle.

From this last bushing, you need to figure out how to connect to your vacuum pump. I prefer to use ½” milky white polyethylene tubing and brass compression fittings. The Lowe’s number for the tubing is 22268, and it’s on the plumbing aisle. You may prefer to use a smaller size tubing, or use barbed fittings with hose clamps, or some other method. It’s your choice, but somewhere along the path to the pump you will want to install a vacuum gage to monitor the system, and a small ball valve. Plumb the valve to the open air to give you a controllable “leak” for those times when you want to utilize less than full vacuum on fragile turnings. I found a reasonably priced vacuum gage at www.mcmaster.com. The part number is 3935K32. Two plumbing T’s joined by a close nipple will allow you to put the gage and valve inline.

The last thing you need to fashion is something to keep the lamp rod aligned with the spindle centerline. If it is allowed to move off center while rotating at high rpm’s, it could spell trouble. If you used two jam nuts on the open side of the bearings and one nut on the inside of the rotary adapter, you still have two nuts left in the package. I turned a wood plug to an appropriate diameter and about two inches long. I drilled through it with a 25/64 drill and counter-bored using a Forstner bit so I could mount these last two nuts in the counter-bore with super glue. My lathe spindle’s bore is 9/16 diameter, so I screwed this wood “nut” on the lamp rod and followed it with another “o” ring like I used inside the bearings. After I screw the rod into a vacuum chuck, I turn the wood “nut” on the outboard end of the spindle until the “o” ring is snugged up against the spindle. This is all it takes to line up the lamp rod with the spindle’s centerline and keep it there. When I found out that the club’s lathe had an aluminum handle on the outboard side which had a bore of approximately 1”, I just turned a chamfer on the wood “nut” so it would fit into the handle and perform the centering duties instead of the “o” ring. There is still an ample flat to work against the “o” ring when the rotary adapter is remounted on my lathe. Just do whatever is necessary to insure that your adapter is safe before turning on your lathe.