This illustrates another version of forming hot collars. If the project calls for a number of nearly identical collars, test collars can be made and when the precise measurements are known, a “witness” collar can be formed.
From that template, many copies can be made. To facilitate identical bending the bend points are creased with a fuller die. This can be done by hand with hammer on anvil, treadle hammer, fly press, etc. Presumably, a jig could be set up to make the process even more precise.
Metal bends where it is thinnest or hottest. This is an example of exploiting both tendencies through selective torch heating at the crease.
I first saw an example of these collars lying on a platen table at Flicker Forge alongside the die which made the crease.
|Fuller creases at bend points.|