Brain picking you automotive types. I need to form (flare) the ends of brake line into a trumpet shape from the typical ductile copper nickel alloy 5/16" diameter. Its not for automotive hydraulic application, they will be the the induction & exhaust tubes for my model radial engine that seat into the heads. I can post pictures later, but my first experiment was a bit of fail. I made myself a split die plate with a 45 deg chamfer. It clamps the tubing which stands a bit proud. Then I just used a 45-deg tool to lightly tap-tap form the tube ID thinking it would expand the cone. This actually worked great using same diameter aluminum aircraft instrumentation tubing but the brake line is thicker & tougher. At some point I will make or buy the assembly that screws down the forming cone, but that isn't really the issue. The problem is the tubing slides down the die plate hole with much forming force despite it being clamped quite secure. If I support the tubing, I can form the trumpet shape but that wont be feasible on the bent header pipe.
I got looking at commercial die blocks & noticed some have micro serrations in the forming block which I'm guessing is to grip the tube & maybe my issue. Is this common? I thought i saw others that were smooth like a drilled hole but maybe those were cheapos or knock-offs?
My other issue is surface area. My grip band is only 0.125" whereas these blocks look to be 1/4 - 3/8". This might not be enough & root of my problem. Mine is thin because I was envisioning the tubes would be already bent & just the ends required flaring so that band was minimized to accommodate the bend.
I got looking at commercial die blocks & noticed some have micro serrations in the forming block which I'm guessing is to grip the tube & maybe my issue. Is this common? I thought i saw others that were smooth like a drilled hole but maybe those were cheapos or knock-offs?
My other issue is surface area. My grip band is only 0.125" whereas these blocks look to be 1/4 - 3/8". This might not be enough & root of my problem. Mine is thin because I was envisioning the tubes would be already bent & just the ends required flaring so that band was minimized to accommodate the bend.