Modeling help appreciated

Dear fellow-shapers,

im absolutely new to 3D-modeling and although quite experienced in different scientific approaches and complex program environments the inherent logic of 3D-modeling is strange…

I‘m trying to design a dovetail plate with a trapezoid cross-sectional area.
The main body is no problem, but I don’t get the recessed screw-slits to be perfectly aligned in the middle of the plate.

My problem, as I understand it, is that I want to align a sketch with a surface.


Unfortunately I‘m not sure what’s the right approach to get this plate designed.
Perhaps it‘s best to first work with a rectangular sketch, extrude it to a cuboid and get the trapezoid shape afterwards, but perhaps I‘m missing the point in aligning those slits?

Any help is greatly appreciated.

Cheers Chris

Form your trapezoid 3D shape. Then you can either 2X tap on the Top surface and lay out your slots and push them through or you can go to the Bottom view and do same.

Finding centerlines and offsets for the slots in a sketch should be pretty simple, but if you need help, let us know.



Hi Tommy,

this is what I did to achieve the model shown in my screenshot, but I have a hard time aligning the slots in the centerline.

I constructed the slots as following:
I created two 80mm lines made them parallel and closed the first form with arcs on both sides. Afterwards I used the offset tool to create a smaller copy but alas this wasn‘t centered either…
Next I pushed in those slots and defined the depth.

This leads to my dovetail plate with asymmetrical screw-slots.

Cheers Chris

Draw a big X from the 4 ends of the rectangle. This defines the center of your piece. Draw your slots based on dimensions and off sets from this point. Use the Parallel constraints. Seems fairly straightforward.

It can also be done by moving the slot sketches where you want them but this can be more procedural and complicated.



Hi Tommy,

this seems to work…
The approach of defining items in relation to other well defined points is new to me.

I‘ve years of experience with Photoshop and am thus used to just take advantage of alignment tools.

I‘ll have a look in this workflow.

Cheers Chris

Hello Roboticshobbyist,

yes this is nearly exactly what I want.
The slots should be positioned a little more off center in the long axis, but this is easy to achieve (even for me :slight_smile: )

But otherwise this is it! A video would be greatly appreciated.

Cheers Chris

Hi Dennis,

this is exactly what I wanted to create - thanks a lot…

My problem, as Tommy already pointed out, was that I‘m not used to define shapes, points etc. with strict dependency to guidelines, reference points etc.

Since a lot of new modelers emerge due to 3D printing becoming more popular (e.g. myself), it would be nice if there would be a tutorial about general constructing/modeling strategies. I think many of us have a problem with the general approach, not necessarily the usage of the program itself…

Cheers Chris

Hi Chris,
I believe that’s what’s holding up my progress as well. For example, I keep hoping that there will be a video ‘chapter’ along the lines of what you suggest, that really gets into how to use groups rather than just how to group/ungroup, if that makes sense.

Thanks Dennis,
That adds clarity. I was assuming the groups feature to be the preferred way of doing assemblies (re: your last paragraph) so this prevents me from heading off down the wrong path. Your feedback is much appreciated.

  • Gerry

How are you able to drag line vertex and circles around by their points? All I get is the square thing popup and 2 arrows. Am I missing a setting?