Workholding of the Month: Awkward, Oval Cast Iron Part with John Saunders

We had the pleasure of having Keith Rucker attend one of our NYC CNC training classes. Keith is a great guy who does some impressive manual machining. We asked if there was ever a collaboration project we could do - especially where we could use our Tormach PCNC 1100! He said that it was perfect timing, as he volunteers at the Georgia Museum of Agriculture where he's helping restore a locomotive!

The Challenge: Replacing a Vulcan Steam Boiler Hand Hole Cover


Keith had the part 3D-printed as a quick test fit and then sent that 3D printed part off to a casting company to use as the mold positive. Obviously the 3D-printed plastic wouldn't suffice under the pressure and heat of a train locomotive, but luckily the cast iron part from the foundry would. The problem? The oval-shape cast iron part needed a grove machined around its profile to hold a seal ring. This task was easy for the Tormach, but this part had two difficult features; the draft angle from the casting meant soft jaws wouldn't be reliable and the threaded stud that was inserted during the casting process meant work holding was going to require some creativity. Luckily, a set of 2-4-6 blocks made quick work of it. We used the 3/4" x 10" stud cast into the part to hold the part securely to the 2-4-6 blocks. We then used the Tormach PCNC 1100 with Haimer Zero Master as a pseudo-CMM machine to determine to points along the profile of the oval. This let us update our Fusion 360 model to accurately reflect the angle that the hand hole cover was at when we tightened the nut down.