Threadmilling 2" NPT Flange Fittings

We used to make these Inlet/Drain Flanges the hard way. We would saw 1/4" x 3" Hot rolled steel into 5" lengths, then Holesaw or Trepan (Hougen Rotabroach) a 2.0" hole in the center. The next step was to purchase and wire weld a 2" Threaded coupling to one side of the strap. This left us an expensive, warped flange that we used for many years. We built a master pattern,then a matchplate for the pictured flange. We greensand cored the center hole to leave only the stock necessary for threading 2" NPT. CNC helical technology allows us to Threadmill, however we had to fool the machine into thinking "TAPERED threads". We did this by breaking the circular interpolation into quadrants and stepping out the "I & J" (Pole of revolution) for each quadrant. We wrote the program in an incremental loop, allowing us to execute a roughing and a finish pass using different tool diameter offsets.

View of 4-up fixture using Mitee-Bite Wedgelocks

Basket of Flanges ready for Installation on new molds built In-house or for sale to our competitors! Current Price is $8.00 ea. Check your labor/materials to build these yourself. They cost us $17.00 ea. 5 years ago.

Closeup of Advent 5 flute inserted Threadmill. Each part in the fixture is threaded in a single roughing revolution, leaving .010", then a finish revolution takes the part to guage size. We use coolant more to keep things cool and the dust down than to lubricate the Cast Iron. The Advent Threadmill has enough flute length that we rough on the upper portion of the tool where it is presumably stiffer, then shift the tool up for the finish pass to expose new bite at the bottom that sees less wear, sand, etc. A set of inserts lasts about 500 parts. We started with a single lip insert tool that only lasted 40 parts. Inserts cost about $37.00 ea and it takes 5 of them. They change out and re-index perfectly in about 5 minutes.

CNC G-Code program "O31 Setup" and "O32 Body" used to threadmill a 4 part fixture load on our Fanuc OM control...