De-Burring Large Diameter Threads

[NickA]

Does anyone know a good method to reduce the sharpness of large diameter threads that were cut on a single point lathe.

We have a large hydraulic cylinder tube (21.5" diameter UNC threads) that has very sharp edges on the internal threads. When we attempt to screw in the mating end caps the threads cut into each other. We would like to round the ends of the threads near the lands.

My first thought was emery cloth or very fine sandpaper but I don't know how effective that will be. Anyone done this before?

 

[11echo]

I've cut threads with a lathe before, but only up to 12"dia. What I used was just a fine mill file, it does a good job with a light touch. BUT that was when the work piece was still on the lathe. Not sure if your trying to handle your cylinder threads the same way? IF not, you could try a Scotch bright pad. I've used these a number of times to de-burr edges on machine pieces. Mount one of these pads to a rotating tool and buff the threads, that should smooth out the sharp edges. NOTE, don't mount this pad to anything rotating faster than 15,000 rpm!!! GOOD LUCK! ...Mark