@Steinwerks
I completely agree with your assertion. I use Mastercam for Solidworks at work and it supports a sketch to be used as a custom tool OR solid model to be used. But even with what I have it is some what limited.
In my older days programming in both Pro/Engineer NC and UGII I could do a SKETCH FORM TOOLS ON THE FLY. But wait there was more... Way more...
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More importantly the sketch allowed for MULTIPLE TOOL CONTROL POINTS. Each would influence the tool path calculation. In one tool sketch you could have the following set.
1) Standard Control point on tool axis C/L and TIP.
2) Control Point on a point on side of tool at contact of geometry. (correlates to an edge on a thread model OR Multi Tool Chamfer Point)
3) Shifted points to simplify setup. This allows setting off the tool tip but the math is shifted to some contact point.
4) As many other control points to add if you need them...
EDIT: A good example would be today's multi function tools, see added tool graphic
In each of these cases the tool path is calculated and output differently to allow driving off existing math OR to simplify setups.
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Most importantly each point type was available for each new operation within the same setup. And each would allow the tool to act independent of an prior existing operation. Again calculating unique to that operation based on the Form Tool Control point selected.
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Each one could have a unique Tool Offset number assigned to match further refinement on the Control.
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All of that was in conjunction with the various type compensation methods like computer, wear etc...
And this is why I made the prior assertion in reply to @bensbenz that I can still do crazy stuff just by doing sketch work.