I have eight pieces of teflon tubing to machine today for a repair on a dough roller. Each piece of teflon is 7-5/8" outside diameter with an inside diameter of 4-3/4" and came in at just over 17" long. I would estimate each piece of teflon would cost between $750 and $1000 each.
I need to cut them to a specific length and bore them to around 5-1/4" with a tolerance of +/-.004 After I'm done, four of them will get pressed onto a stainless steel roller and machined to a specific diameter.
First two videos show the Daewoo 600 CNC lathe using a carbide cutoff tool to cut the tube close to finish length. Teflon is soft and distorts easily so I am holding in in "soft jaws". Soft jaws are steel and in this case, bored to a certain diameter to hold the teflon over the entire length.
The hydraulic chuck is 24" in diameter and the jaws are made out of 3" square hot rolled steel, 14-1/2" long. It's spinning about 600 rpm
same operation, slightly different view. the safety glass is designed to absorb an impact and a replacement piece was $750 about 12 years ago ( not I, a former coworker
Now the end that was just cut off square is placed against the chuck. The machine is programed for "constant surface feet" so as it faces ( cuts ) and gets smaller, the RPM increases. The tool used can either face ( as shown ) or turn the diameter.
I also put a countersink using a boring bar
This is the final operation. The part is flipped end for end and faced to length. Then a very stout homemade boring bar is used to cut the inside diameter ( bore ) for a total length of 15-1/4" After each cut, I turned off the spindle and removed the chips so they don't jam against the boring bar and "do nasty things" ( like melt
Teflon can be cut dry or with coolant. I cut it dry so I could video this for you folks