1. First determine to what size you need to enlarge the inner diameter of the tendon tube. Tendon tubes are usually made of rubber or plastic, so they can be expanded more easily by heating or softening.

2. Next, insert the pipe expansion tool into one end of the tendon pipe and gradually expand the pipe until it reaches the required size.

3. Finally, you can try to use manual methods to enlarge the tendon pipe, insert it into the tendon pipe, and slowly rotate and push it in to expand the size of the pipe.