it was done in my lathe and was done using countersink bits with the lathe being turned by by hand using a handle but in the reverse direction
but the metal was moved using countersinks in reverse. if you try to use a centre, its fine to start with but as the cone gets bigger you need more and more force as the contact area gets bigger, and the tube needs to be well supported so it doesnt collapse (and why a collet chuck is better than a 3 jaw chuck.) These are the tools I used
I used the smaller countersink to start the centre and because it only partially contacts the cone of the funnel it allows the copper to stretch and uses less pressure than a centre.
and then it waas necessary to use a different type of countersink and use a small screwdriver in the gap to move the metal. the copper needed to be annealed a couple of times and the countersinks were swapped a few times too..
now if you have enough force and suitable dies you could do something called impact extrusion, put a slug of metal into a press and apply a huge force and it has to go somewhere
or you can start off with sheet metal and do deep draw transfer pressings
and back to forming a funnel shapem Im planing on making a new exhaust for my car and where it joins to the manifold is like a funnel shape, I tried this by forming it, but that ended up in the bin, I'll weld the cone part from sheet and weld that to the tube.
but the metal was moved using countersinks in reverse. if you try to use a centre, its fine to start with but as the cone gets bigger you need more and more force as the contact area gets bigger, and the tube needs to be well supported so it doesnt collapse (and why a collet chuck is better than a 3 jaw chuck.) These are the tools I used
I used the smaller countersink to start the centre and because it only partially contacts the cone of the funnel it allows the copper to stretch and uses less pressure than a centre.
and then it waas necessary to use a different type of countersink and use a small screwdriver in the gap to move the metal. the copper needed to be annealed a couple of times and the countersinks were swapped a few times too..
now if you have enough force and suitable dies you could do something called impact extrusion, put a slug of metal into a press and apply a huge force and it has to go somewhere
or you can start off with sheet metal and do deep draw transfer pressings
and back to forming a funnel shapem Im planing on making a new exhaust for my car and where it joins to the manifold is like a funnel shape, I tried this by forming it, but that ended up in the bin, I'll weld the cone part from sheet and weld that to the tube.