When you scale an object and enter an absolute size with a unit, that the object has that entered size.
So far, so good.
But I need a methode to reduce the size of the object by e.g. 4mm.
I don’t want to use the move tool or the offset tool.
Because the scale tool has more axis and more option in general.
Thanks for your advice.
You could draw a temporary guideline for this.
I tried that. It allows to reduze/increase the size along one single axis.
That’s not far away from the usage of the standard move tool of SU.
May be I have to describe a more complex task to explain my issue.
I have a door at a simple furniture. It has, as the first construction step, the same size than the corpus of the furniture.
Now I like to reduce the size of the door (e.g. 50cm x 80cm x 1,8cm) at the left, right, top and above by 0,4cm.
The resulting size should be 49,2cm x 79,2cm x 1,8cm
The standard scale tool from SU offers the perfect “line” for that.
I hold the ALT key (on macOS) and choose the diagonal line inside the door.
Now I can scale exactly in the way I want in one single step.
But I can only enter a proportion (e.g. 0,95;0,95) or absolute measurement (49,2cm;79,2cm)
The task is standard task in the construction of furniture. Many times you need a face joint (I hope that is the correct translation of the german word “Fuge”) for doors.
I’m looking for a tool which allows to enter just “0,4cm” and all is done.
Because the task is “reduce the size equally at all 4 sides by 0,4cm”
Do you have idea how to do that elegantly?
@eneroth3
Yes, it would work with guidelines, but that is not a fast method. I’m looking for a really fast way to solve that standard task.
Not quite sure, you do know you can type all 3 measurements?
49,2cm;79,2cm;1,8cm
Yesterday I tried FredoTools Box Stretching. But that tool does not offer a diagonal. So it is impossible to perform the task in one step.
That would be not fast and comfortable. You have to reveal both measurements before, have to calculate in your head, you have to type many ciphers, …
The task is just “reduce the size by one single absolute measurement” 
You can use FredoScale
Select the object and call FredoScale Box Scaling tool.
Hover over a handle
Type TAB
The dialog box will show the dimension or dimensions depending on the handle chosen
You can use formula in the fields, so you can type an increment, ex: ‘+ 10’, including using units.
Since FredoScale allows you to set the axes for scaling, you are not limited to the model axes or object axes.
Now I found a workaround.
You can use the standard SU tool “offset”.
There you could enter 0,4cm. After that step you have to use Push/Pull to “carve away” the outside.
But still it would bei nice to have a generall methode for the scaling tool, to reduce/increase instead of entering the resulting measurement.
SketchUp doesn’t do calculations like that through the ‘Measurement’ box. It accepts scale factors and exact values (plus units), not -4 cm for say two out three dimensions.
That works perfectly.
No problem at all that you have to enter the addition twice for both axis.
Thanks a lot Fredo6! Not only for the hint, but for all the great work in your tools!
Now I see a mistake in my conceptional understanding.
Using a diagonal for scaling, you cannot add a measurement for another line but the diagonal.
So you have to use 2 steps, that means, you have to choose the plane of y-z and the plane of x-z.
May be therefore the methode I mentioned “Offset and carving away” is the best method for the task.
Because there you can add one single measurement.
Fredos Joint Pushpull.
Thanks for the hint to JointPushPull.
As a beginner in SU that complex tool seems to be not easy to understand/handle. I will put it to my ToDo list.
