There are a few possible reasons for the flex shaft sheath to melt. The cable inside a flex shaft machine is turning at high revolutions per minute (RPM’s). This can cause some potential issues with the outer sheath.
Every situation is different, and I don’t know what your exact situation is, but here are some general pointers that may help you identify the problem.
The inner cable that spins within the sheath is lubricated with a thick high temperature grease. The outer sheath may have melted for a few different reasons based on this:
- The inner shaft was not greased enough.
- The grease was heated too much and slid away from the area of the sheath that melted.
The most common issue is that the shaft is flexed to sharply meaning that you are applying to much of a bend in the shaft. (This is indicative of the shaft melting at the hand piece.) If the shaft is kinked to tightly the spinning of the inner shaft will create friction. This friction heats up the grease to a liquid state. The grease then will flow away from one area, and this can cause the outer sheath to melt.
Some suggestions for solving this in the future may be:
- To ensure that the position of the motor allows for the shaft to have less of a bend. Some flexing is fine, and they are designed to be flexed. But they do have their limits.
- Check that the inner shaft has sufficient grease applied to it. It does not take a lot, but make sure the entire shaft is covered.
It is always best to keep in mind the amount of time you spend carving with your flex shaft machine. If you do not use it that often you may not need to check the grease as often, but at the same time this may warrant checking it every time you use the tool.
I have found that setting up a Maintenance Schedule for my tools helps me to ensure that I do not run into situations where I have to replace parts or tools.
Pulling the outer sheath off the cable does not take long, and visually inspecting the cable from time to time can really save you some headaches and possible injury in the future.
Most importantly; work within the limits of the tool.
Every tool has a limit, and every time you exceed that limit it places more stress on the tool. Eventually you will have problems.
Finding the limit is not a science, and there are no hard and fast rules to go by. This comes with experience, practice, and patience.