Second Semester: Week 2

This week I learned about casing repairs. This included thread repairs, casing dents and piston action. First I worked on thread repair. The first thing to do with thread repair is to make the casing round. I did this by finding the correct size dent ball that fits in one of the other casings. This allowed me to start with an undersized dent ball and work up to the correct size because there was a lot of damage.

Damaged thread casing

Some of the threads are blown out and some are dented in

Undersized dent ball that I started with and continued to move
up in size to get to the finished size

After the casing was back to round I checked to see if there was damage to the lead thread. In this case there was no damage and I could proceed by using the cap to chase any damaged threads. I put the cap on and once I felt any resistance I tapped the cap with my rawhide hammer. This allowed the threads to form to the threads in the cap. After chasing the threads to the bottom my thread repair was finished.

Finished threads back to round, threads in the cap fit nicely
and the cap is easy to remove

I also worked on casing dents. Casing dents can cause a piston to perform poorly. When working with a casing dent the first thing is to remove the piston as carefully as possible and not cause more damage to the piston or casing. Once the piston is removed I inspected the dent.

Dent on the second casing below the slide tube

The dent is causing the second piston to get
stuck lower than the other pistons

You can see the light reflecting off the raised area where the
dent is

After inspecting the dent I used a ground casing mandrel that coordinated with the make of the instrument and multiple hammers. I started with the rawhide hammer and a utility hammer to hit the rawhide which was over the dent. Then I moved to the small delrin and I finished the area with a small steel dent hammer.

The finished dent. The high spots have been pushed down and
the piston works in the casing