This post describes the process that I used to shim the bearings in my Shapeoko 3 V-Wheels. This process could be used for any V-Wheel assembly whether it’s used on a Shapeoko or some other machine.
The V-Wheels that I received with my Shapeoko 3 were out of tolerance (no fault of Carbide 3D) and the centering ribs were too thin. This lead to the bearings being able to move back and forth in the wheels, causing a loss of accuracy.
Here we go.
First, go to McMaster-Carr and order one package each of the following packages of shims:
- .003″ shims p/n 93574A430
- .005″ shims p/n 93574A432
- .007″ shims p/n 93574A434
- .010″ shims p/n 93574A436
- .020″ shims p/n 93574A438
They come in packs of 25, which is more than enough to do all the wheels on your S3.
Next, disassemble all the v-wheels. I used a socket to support the wheel and a small screwdriver to lightly tap out the bearings. It doesn’t take much force to get them out.
The bearings and existing shims are pretty consistent in their thickness, so you don’t need to worry about keeping them together with the wheels they came with. I just tossed all the parts into a container.
Next, make a copy of this Google Sheet that will calculate which shims you need for each wheel.
You will want a way to mark the wheels so you can keep track of which one is which when it’s time to shim and assemble. A piece of masking tape will work. I used some tags that I bought a while ago. You could write on the wheels with a paint marker if you want.
The spreadsheet is designed to use thousandths of inches with no decimal point. So a measurement of 0.129″ would be entered as 129.
Measure each wheel. First measure the thickness. Enter the value into the spreadsheet in the Wheel Thickness column.
Next measure the distance from the face of the wheel to the rib. This can be a bit tricky, so I repeated the measurement three or four times around the diameter. Make sure you don’t get hung up on the small radius at the bottom of the rib. The numbers should be in the range of 0.127″ to 0.133″. Enter the number in the Rib Depth 1 column.
Repeat for the other side, entering the number in the Rib Depth 2 column.
The sheet will calculate the rib thickness and the shim stack to use to match this thickness. For example, a Shim Stack of 2×003, 1×005, 1×020 means using two 0.003″ shims and one each of 0.010″ and 0.020″.
Next assemble the wheel again using the shims called out on the spreadsheet. You can just press the bearings in with your fingers. I used a wheel bolt to keep the shims centered during assembly.
Once the wheel is assembled you can double-check the fit by measuring the total width across the bearing faces. It should equal the value in the Total Stack Up column.
The last column – Plate Shim – is the amount of additional shim that you should put with the washer between the bearing and the carriage plate to make the V-Wheels as co-planer as possible. You may have to fudge a little one way or another – using a 0.003″ or 0.005″ shim when it calls for 0.004″.
I would suggest using the original bearing shim washers between the wheels and the plates. They are a little thicker than the ones supplied for this purpose, but they are much more consistent in thickness. Mine all measured within 0.0005″ of each other while the supplied washers ranged from 0.032″ to 0.039″ in thickness.
If you follow this procedure your v-wheels should have no bearing slop and be as co-planer as possible.