Joining polyurethane belting
A common workshop requirement, especially for small machines. Of course the ends are heated and fused together, but how best to do so?
A couple of factors to consider
- The belt ends must be perfectly aligned, if they are off, the irregularity will create a vibration as it passes over the pulley
- For maximum strength, the melted ends must be held fixed and allowed to cure for 30 minutes. This is from the belt manufacturer, and from experience, one the smallest of diameters this absolutely required to create a belt that doesn’t break.
- You don’t want to get the material too hot else it burns and the chemistry is spoiled. This means no direct flames
The device is simply four pieces of mild steel aligned with dowel pins. the ends of the belt are clamped in the left and right halves, with a gap between the steel pieces.
You leave a little bit of urethane protruding into the gap
A knife is heated by an alcohol lamp. Holding it by hand is the norm, I just used the vise so I could work the camera. Hot knifing of a different sort than that of a misspent youth.
It is easy to use in situ
Clamp and wait 1/2 an hour
Perfect joints result!
with a bit of trimming, the joint is barely visible
