Facing tool path does not correctly use stepover

[ashes.man]

I was playing with stepover and noticed that it does not seem to work correctly.  I though the facing too path was quite a simple one and that each pass would be exactly separated by the stepover distance.  But every value I enter for stepover results in an actual stepover much less than this value.  Example, using a 50mm face cutter, say I want a 47mm stepover, the actual tool path I get has a 25.845mm stepover.

How can I get it to use my stepover?

Also, I would like the area where the tool overlaps to be down the center of the part, hw can I offset the toolpath?

Picture and example file attached.  Note in the picture that the Y dimension of the part is around 50mm, so you can see the tool path stepover is much less than 47mm.

Thanks in advance

[ashes.man]

Just as a follow up, I was able to fudge the tool path that I wanted (sort of), by setting the stock offset to 22mm and stepover to 60mm.  This is not ideal for a few reasons; I cant really use it to make a template operation, and the stock offset causes the tool to have excessive lead in and lead out.

[a.laasW8M6T]

So the first pass is at 47mm but then it looks at the remaining stock and says well i don't need to take that large to remove that so it does a smaller stepover.

You can lie to it and say the stock is bigger than it is:

and it gives a result close to what you want:

If you want perfect control over the positioning of your passes you will have to use 2D contour.

[a.laasW8M6T]

Sorry didn't realise you had replied while I was typing my reply, I'm not sure if there is an easy way to get it to do what you want to store as a template.

I tried using the Flat toolpath too but I can't get that to produce desirable results either.

I assume you want this more for aesthetic reasons rather than any practical purpose?

[DarthBane55]

The facing toolpath is really rudimentary.  In your 1st picture, when it goes for the 1st line, it does climb milling, but when it comes back, it's conventional milling pretty much.  That's ok on finish pass but when roughing it's not great.  It also barely overlaps the material on the return line, the only way to cheat it is to add a bit of material offset, just to ensure a good overlap to the outside edge. 

The return line should be on the outside of the part or in a similar distance to the edge than the 1st pass (take equal amount in both passes with a bit of an overlap in the middle).  Your idea of offsetting the toolpath is excellent, I would use it pretty much all the time.  At least we can easily do a 1 pass facing, so that's a bonus (some CAM can't do it!).  But it would be great to specify how many passes we want, so in your case, you don't worry about stepover, you'd just put "2 passes" and it would center the 2 passes on the material (up to you to determine if 2 passes cleans it or not).

Many things we could wish for, but the facing toolpath is really basic, and has not changed or improved in years.  Maybe a little overhaul would be cool 🤔

If you need ultimate control, like @a.laasW8M6T said, use 2d contour with compensation set to "off", or even sometimes you need to cross over the path itself, you can use trace.