Joining Timing Belts for 3d Printers etc.

So you have a timing belt for a 3d printer or something and you need to create a loop or lengthen it.  The first (untrue) thing I’ll say is the same thing everyone else on the internet says, “You shouldn’t join belts they have to be made the right size.”  Right.  Now that’s been said, if you should find yourself needing to do it anyway, here’s how I go about doing it.

What you need:

• Small needle
• Nylon thread (thin and strong is the key here, so it has to be nylon)
• Hot glue (optional but recommended)
• The belts you wish to join.  (duh!)

Start by cutting the 2 ends you wish to join together as neat and square as possible.  The idea is for the teeth spacing to look continuous and normal when you put the 2 ends together.  You can see in the above image I’ve cut 2 pieces of belt to demonstrate.

Next up, start sewing the thread through one side of the belt and tie it off really well.  Then proceed to stitch the 2 pieces together, pulling them close to each other as you go.  I’ve used a criss-cross sort of pattern as you can see above.  The more stitches you do, the stronger the join is going to be.

In the above image you can see the 2 pieces have come together quite well, although the thread is bridging the gap between teeth.  This is fine in most cases, but if you’re being pedantic, you can use a stanley knife or xacto to cut little slits into the teeth to let the thread fall into.  I don’t bother and it works fine for me.

The last step I usually do is to tie off the thread, then apply some hot glue to the join.  For the teeth side, I put a blob of hot glue then press some timing belt on top to kind of shape the hot glue to the shape of the teeth.  On the back I just put a blob of hot glue on the table then smoosh the join down on top.  You end up with something like what’s pictured above.

Finally, I trim the hot glue and excess thread back and I’m left with a nice solid join like you see above.  The strength of the join depends on the nylon you use and how many passes in stitching you make, so it’s up to you to match your needs.