SolidWorks question: mating flat bearings round holes to C-channel square holes

I’ve been trying to teach myself how to learn SolidWorks and things were going fine until I tried to mate a plastic flat bearing (part 276-1209) to a C-channel. Getting the round holes to line up with the C-channel square holes seems to pose a problem. So I tried little tricks, such as getting the bearing’s little nubs, various faces, edges, etc. to somehow line up with the inside of the C-channel holes. I keep getting errors that suggest the plastic bearings have some kind of angles on their faces (perhaps as part of their design in plastic molding, etc.?). Or maybe I’m doing something really stupid.

Does anyone know how to deal with this? I know Team 3547 “Virus” has some parts they modified to make mating much easier in cases like this, but I’m trying to find a general solution to this problem, if there is one.


You are probably going to want to draw a 2D circular sketch on the metal. Obviously make sure the circle fits exactly inside the hole.

Inventor makes this a lot easier because of the imates. I strongly suggest switching and using the BNS(Jordan’s) library.

The bearings have a slight taper on all sides (called “draft”) which is designed into the part so it can be released from the injection mold during manufacture. After mating the main “flat surface” of the bearing to the vex metal, select only the edge of the bearing (it will be a line) rather than the side surface of the bearing. That line can then be mated to planer surfaces without the errors you’re encountering. To “tabor473’s” comment, the parts I modified with circular features are essentially the same, and that would be the easiest way to do it. If you don’t want to modify standard vex parts, the bearings can be aligned precisely centered over the holes using a “width mate” which you’ll find in the advanced mates. Select two opposite “square hole” sides as the “width selections” and select the round hole of the bearing as the “tab selection”, and the round hole will center itself on the vex metal. Repeat for the other direction.

What I usually do is take one of the bearing block’s holes and tangent mate it to two sides of a c channel hole. Then I use another tangent mate to connect the third bearing block hole to another c channel hole.

This will gets the job done…but realize the round hole will not be exactly centered over the square hole. The “CAD Purists” will have a cow!

Excellent! That sounds cool. I’ll have to learn how to do that. Thank you! That’s the kind of suggestion I was hoping for.

In the meantime, I kluged a solution by creating a “Bearing Alignment Tool”, which is a 3 inch long cylinder with a diameter of 0.180 inches. Because the standard Vex hole is 0.182 inch square, this tool fits fairly tightly into the hole when I make it tangent to 2 orthogonal sides of a square hole. I first insert a couple of these alignment tools into the square holes of the C-channel, and I then make the bearing holes concentric with the bearing alignment tools. After that, I delete the alignment tools. Yes, it’s a tedious approach, and I’m sure it, too, upsets the CAD Puritans, but I wonder if there would be any real downstream issues (interference warnings, etc.) caused by using an alignment tool that way - anyone know for sure?

Thanks, everyone. I’m glad to know there are others using SolidWorks around here.

If you “hide” the alignment tool, then no, but if you delete it, you’ll lose the mates. But using a “tool” isn’t much difference than using the parts with a small cylindrical feature added to each hole.

I just tried your suggestion and it works great! The fit is perfect and it’s easy to do. Thanks again!

I am a novice at this as well but the part library that I have uses the iMates. Highlight the bearing, hold down the left Alt key (if on a PC) and drag the white marker on the bearing to the white marker on the c-channel.

Alternatively you can use the Constrain, select the Insert button, select the hole on the bearing and then the hold on the c-channel.

iMates are a feature of Autodesk Inventor, not SolidWorks. Something somewhat similar is available in SolidWorks called “mate references”, but no one has ever bothered to build a library of parts with them (and I don’t expect one to be built either).

Sorry, I missed the SolidWorks reference.

I have a complete parts library with all circle mates cut into everything for easy concentric mates.
Some complex assemblies are now stored as part files to reduce space also, making it more efficient.

I can release that if people want.

Credit for structure parts goes to Team Virus.

The best and correct way to mate the Bearing Flats to the VEX Metal in Solidworks is as follows:

Start by doing a coincident mate with the flat side of the bearing flat to the side of metal its being installed on.

Then, utilize width mates to finish locking the part in. First, go to advanced mates, then click the width mate button. You’ll notice that in the mates menu there will now be two selection windows. First select two parallel sides from one of the square holes you want to mount to. Once you’ve selected two sides, Solidworks will automatically switch to that second selection window. Now if you click the round face ont he bearing flat that you are mounting to, it will center that hole between the two faces on the square hole. Once you’ve done that first width mate, you can do another width mate on the same square hole but with the other two sides. That will lock that round hole on the bearing flat to that exact hole on the metal. From there you can either do a third width mate on the other square metal hole to the other round hole on the bearing flat (I would suggest this) or you can select the straight edge of the bearing flat and make it parallel to the vex metal.

The right way isn’t always the fastest but I highly suggest using this method over making circular sketches. It is worth it in the long run and once you get used to it it really doesn’t take that long.

Yes, Mr. Mohn (kmmohn), suggested the width mate approach up above and I found it very easy to use. I also agree that using the width mate to “lock in” two holes of the bearing is probably better than locking in only one hole and then using parallel edges or whatever to align the bearing: it’s sometimes tricky on plastic parts to get an edge that can be parallel at the same time it is face-to-face elsewhere on a metal part. This is caused by the plastic mold “draft” as Mr. Mohn explained earlier. It’s a very good “learning opportunity” for kids (and me) to encounter this problem.