Wood U-joint Fidget

This Fidget is a Universal Joint, commonly referred to as a "U-Joint". The U-joint is found in many automotive applications. This is a small handheld woodworking project. The project does not require a lot of resources or skill.

Although the original U-Joint design was not designed to be a wood working project, credit must be given to the author of this FreeCad tutorial that presented it.

(7) FreeCAD 0.19 | Create Assembly Practice 06 | Manipulator WB - YouTube

Since it is a small handheld project, only small scraps of wood are required to make it.

The primary power tools used were band saw and drill press.

The primary wood used is any scraps you have laying around. I used Black Walnut and Maple.

Small pieces of 1/8" and 3/16" wood dowel are also used.

The completed U-joint is the heart of the Fidget, figure #2. The core of the U-joint is shown in print #3. It is simply a small 1/2" x 1/2" x 1/2" block of wood, figure #4. I used Black Walnut just for the cosmetics.

The illustrated parts will be shown with different colors to better show the assembly process.

Drill a 1/8" hole all the way through on two sides, print #5. Drill one hole on any side and then drill another hole on any other side, figure #6.

We need four pins for the U-joint. The pins are made from 1/8" wood dowel, print #7. Each pin is 3/8" long. Lightly round off one end on each of the pins with sandpaper, figure #8. Do not insert the pins in the core yet.

A "Yoke" is used to support the U-joint, figure #9. Note that there are two Yokes required, figure #10. The two Yokes are identical. The Yokes should be made from a good quality sturdy wood because the parts are small and have close tolerances. I used Maple.

Cut the basic block of wood using the dimensions in print #11. The block should look like figure #12.

We need to drill a hole in each Yoke to allow connection to the U-joint. The hole can be drilled on either end of the block as shown print #13. The block should now look like figure #14.

Cut the opening for the U-joint as shown in print #15. Pay special attention to the location of the U-joint mounting hole as shown in figure #16.

Drill the hole in the end of the Yoke as shown in print #17. Drill the hole all the way through. The Yoke should now look like figure #18.

Using print #19, make the final trim cuts. The Yoke should now look like figure #20.

Remember you have to make two of these.

Insert the U-joint core into the Yoke as shown in figure #21. You probably will find that it won't fit. Sand equal amounts off each side of the core until it rotates easily in the Yoke.

The Yoke is complete so it's time to sand all the edges for cosmetic purposes. The ends need to be well rounded as shown in figure #22.

The core should have all of the edges lightly sanded as in figure #23.

The assumption is made that you completed TWO Yokes so it's now time for a little assembly. Do not glue any pins or shafts until the project is complete and tested. You may find that it won't be necessary to glue the pins or shafts because they have a relatively tight fit without the glue.

Insert the core into one of the yokes and line up the pin holes as in figure #24. In Step #2 you made four U-joint pins.

Insert one of the pins into the Yoke with the rounded edge sticking out. The pin should be inserted into the core to the edge of the center hole as shown in figure #25. Do the same thing with a pin on the opposite side, figure #26.

Attach the second Yoke, figure #27. You won't be able to see the center of the core when inserting the pins to check the insertion depth. The amount extending out from the Yoke should match the other two pins already installed.

Cut two pieces of 3/16" dowel 1 1/8" long. Insert one piece in the end of each Yoke, figure #28. The depth is not important since it is temporary.

Now you can test the completed U-joint. Hold one end and bend the other down about 15 degrees, figure #29. Rotate one end. The assembly should rotate smooth without any restriction.

Now that the U-joint is complete we need to add a bracket to mount it in, figure #30. One of the sides has a 15 degree offset to better demonstrate the flexibility of the U-joint.

The bracket is 1" wide so you may have to glue two pieces together to make 1", figure #31. The dimensions for the initial bracket block are shown in print #32.

Note: You will find it to be easier to make the block ~4" long initially rather than the 2 5/8" called for in the print. It will be easier to make the angle cut in the next step and then it can easily be trimmed down to 2 5/8".

Make a 15 degree angle cut on one end of the bracket block as shown in print #33. Photo #34 shows how I made the angle cut. The block should now look like figure #35.

Remove the section of wood as shown in print #36. Both sides and top should be 3/8" wide.

Each leg of the bracket has a hole to support the U-Joint assembly. Each hole is 13/64" to accommodate the 3/16 drive shaft and follower shaft. The straight leg has the hole 1" from the bottom. The angled leg has the hole 3/4" from the bottom as in print #37.

I used a platform to drill the holes as shown in figure #38. Cut two blocks of wood exactly the same size. Stand them both on edge. Place a scrap piece of wood over the top of both side pieces. Place the leg flat on the top surface as shown in the photo and drill the hole. Do the same with the other leg. Make sure both legs are flat on the surface of the platform when you drill the holes.

Sand all the edges of the bracket. Round the sharp corners as in figure #39.

The U-joint was assembled in step 11. Pull the shafts out of each yoke. Place the U-joint in place in the bracket. Insert a shaft into each yoke through the bracket as in figure #40. The shafts should be inserted 3/8" into the base of each yoke.

Rotate one of the shafts to test the mounted U-joint. It should turn easily without any hesitation.

Round off the tip of the follower shaft. The follower shaft is the one that fits into the angled leg of the bracket.

We'll add a small crank to the drive shaft. The drive shaft is the one that fits into the straight leg of the bracket. The dimensions for the initial block for the crank are shown in print #41.

Drill a hole for the drive shaft and one for the crank handle as shown in print #42. Round the ends as shown in figure #43.

Cut a 3/4" piece of 1/8" wood dowel. Round one end. Insert the other end into the crank 1/8" hole. The end should be flush with the side of the crank as in figure #44.

Install the crank onto the end of the drive shaft. It should be ~1/16" from the side of the bracket as in figure #45. Cut off any excess from the drive shaft that extends beyond the edge of the crank.

Your U-joint fidget is now complete, figure #45.