Trumpet Slide Tube Mandrel

This is a quick project that creates a very useful brasswind tool. A slide tube mandrel is used for repairing and rounding inner slides on a trumpet. It is made of a brass 1/2" bar with a threaded rod. 

Photo credits to my bench-mate M. Parks.

I start by facing the brass stock on one side, then de-flashing. The stock is about a foot in length and will later need to be cut to size. 

Next, I begin to turn the stock down to its new diameter, from .500" to .458". This is done using the dial on the cross slide. I remove about .010" at a time until the final pass. Between each pass, I measure the diameter with calipers to confirm how much more material needs to be removed.

After turning, I drill out a hole to be tapped. Then, I cut off the needed part with a hacksaw and face the new side.

Finally, I tap the drilled hole. Additionally, I round the edges of the mandrel with a bevel to prevent any potential marring of the slide's interior

Done!