Introduction: 3D Printed Jigs for Eccentric Lathe Turning

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About: If its practical, I have no use for it!

For Valentine’s Day I wanted to make a pretty wooden pendant on my lathe. There are a lot of instructions and videos on the web teaching you how to do that. They all involve making some kind of jig to create an eccentric hole and pattern. There are commercial jigs available, as well as many ideas for making your own jig from wooden parts. I wanted simple, so here I came up with a design that you can 3D print, mount in your lathe chuck, and make your pendant. I have not seen this idea and design anywhere else.


Supplies

  1. Small pieces of wood for turning
  2. Lathe
  3. 3D printer and filament
  4. Turner's double-sided tape, CA glue, or hot melt glue

Step 1: Overview, the Short Version

My process of making a pendant is like this, with more details in the steps below:

(1) Create a pendant blank from a 1” thick piece of wood using a 1.75” hole saw.

(2) Mount the blank in your lathe and flatten one face.

(3) Make a round waste block just like the blank, and use double-sided turner’s tape to stick the blank to the round waste piece.

(4) Use the centering jig to mount the waste block/blank into the lathe, round the blank, and dome-shape the face.

(5) Sand and polish.

(6) Mount the waste block/blank into the off-center jig and drill the off-center hole.

(7) Create the concave recess around the hole, and sand and polish.

(8) Remount the waste block/blank into the centering jig and part off.

(9) Mount the pendant (backside out) into the centering jig using the spacers. The pendant backside should protrude slightly from the jig while still firmly clamped down.

(10) Clean, sand, and polish the back face.

Step 2: 3D Print the Jigs

3D-print the following jigs from the included files: centering jig, off-center 5mm, off-center 8mm, spacer 2mm, spacer 3mm, spacer 4mm, spacer 5mm. I used PLA filament, 0.2mm layer height, 50% infill. The jigs should be safe to use; but use carefully and at your own risk!

The jigs are sized for a Nova lathe chuck with 2.5" max jaw opening and pendant blanks made with a 1.75" hole saw (1.6" blank diameter). For other jaw and blank sizes it is easy to modify the design and reprint the jigs.

Attachments

Step 3: Make a Blank

Find a pretty piece of wood about 2” square or larger. Using a drill press and a 1.75” hole saw drill out your blank. Be sure to secure the wood piece with clamps while drilling. Your blank ‘plug’ will be about 1.6” in diameter. I glued up some strip laminations of different woods to create an interesting pattern for the pendant.

Step 4: Shape the Front

Mount the blank in your lathe chuck using the centering jig. Flatten one end of the blank.

Next make a round waste block from scrap wood (I used a 2 by 4) just like you made the blank above. Again, flatten one end.

Mount the waste block in the chuck using the centering jig, and use double-sided turner’s tape to attach your pendant blank to the waste block - flat side against flat side. Try to center the pendant blank as well as you can. Use the tailstock to press the blank against the waste block, and let the tape glue set for a couple of minutes. Alternatively, use CA glue.

Now round the blank and shape the front of the pendant into a slight dome shape. Sand, polish, and finish. I go up to 1000 grid.

Step 5: Making the Eccentric Hole

Remount the waste block/blank in your chuck using the off-center jig. Position the blank so that the hole you will drill next is in a desirable spot; this determines how the pendant will hang when wearing it. At low lathe speed drill a 3/16” hole into the pendant. Next shape the space around the hole to create a concave recess. Sand, polish, and finish the concave space around the hole.

You may also cut some off-center grooves the add interest, see the pictures in the introduction.

Step 6: Parting Off

Remount the waste block/blank in the chuck with the centering jig and part the pendant off. I make pendants about 1/16" to 1/8” thick on the rim. Before taking the pendant all the way off clean and sand the backside as much as you can. Unfortunately, as you can see in the picture, the pendant broke off too soon; I wasn't careful enough. No problem, we'll fix it in the next step. The last two pictures above show a cleaner part-off.

After parting off you may have enough wood left on the waste block/blank to make another pendant. I'll show that in step 8 below.

Step 7: Clean Up the Backside

The backside will need to be cleaned and finished after parting off; especially since I didn't do too well in parting off. Use the centering jig and some spacers to mount the pendant - backside out - in the chuck. The pendant may be flush with the centering jig or protrude slightly depending on how thick it is. This is where the spacers are helpful. Just be sure it remains firmly clamped into the chuck. Clean up the back face with a gouge and sand paper, 150, 220, 320, 400 grid and up - your choice. Finish as desired.

Step 8: Making a Second Pendant From the Same Blank

You may have enough material to make a second pendant from the same waste block/blank. Follow the same procedure as above. Since you already flattened and cleaned the backside, only a little touch-up is required on the back. Remove from the waste block with a flat bladed putty knife, peel and clean off the turner's tape, and lightly sand.

Step 9: You Are Done

That’s it. Add some variety by making pendant blanks from different combinations of wood, glued together in various patterns. Cut some off-center grooves during step 5. Laser engrave the pendant with artwork.