What's new

Adding slot.


Senior Member
I just need to know how I can elongate that semicircle to a slot. I have tried the equations, but, am not sure of what to do. I see how as I add dimensions to my drawing it registers into the equation. My trouble is how do I add a slot depth to those measurements? I can always draw it as a square slot and have the cutter diameter create it. But, if I use a smaller diameter cutter, it would be nice to get a full radius at that point.


Alibre Super User
Uh, what semicircle are you talking about? Do you have a screen shot of the model?

Generally speaking, if you have a semicircle it will consist of an arc and a line. If you want to convert it to a slot then something will be needed to for the straight sides of the slot. That means you need to edit the sketch and add some sketch figures to define the rest of the slot.

If you have "Show Equations" selected in File Properties>Dimensions then each dimension will have its name shown such as D1, D2, A1, etc. You can use these name in the equation editor or in the dimension box. If you wanted two dimensions to be equal all the time then just enter the driving dimensions name in the driven dimensions data field. You can also use a equation when entering the dimension name - say in the dimension field for D3 to be half of D1 enter D1/2 for D3.

You can read more about Equations here it the Help.
Last edited:


Senior Member
In my hurry, I forgot to attach the photo. I have extruded the part with the semicircle in. I then just drew on top of the extruded shape. How do I get it make a slot in the part? Thanks.
Screenshot (88).png


Alibre Super User
I borrowed your image and marked it up. Remember that sketches need to be closed before they can be used to create features on the model. It might be easier to remember that when creating a sketch for a feature just "close the loop".

Is the semicircle sketched into the base part or is it a new feature and you are editing its sketch?



Senior Member
What if the slot is on a circle? Do you still just draw it across? Or does it need to be the circumference?Screenshot (96).png


Senior Member
Hey Papajoe41,

some basic hints:

1. Take a piece of paper and draw your part with a pencil, post it here.

2. Think in simple Volumes. You can extrude/revolve Sketches and add Material or you can extrude/revolve a sketch and subtract Material. Also sweep a sketch a long a curve is possible to add or subtract Material.

3. With this knowledge split your geometry into several of These simple Operations until you have your desired geometry.

4. Constrain/Dimension your Sketches properly until they are fully constrained, that is essential!!

In this case use:

1. One sketch for cross-section of the sweep subtract = circle
2. Second sketch is the sweep-path it starts in the middle of the circle of sketch one and is orthogonal to it = two lines connected with a Quarter circle.

Hope this helps - Keep it Simple.


Alibre Super User
In your image just draw a line across the end to close the sketch, it will still cut the slot.

IF you need to dimension the slot from the OD of the part then I would still draw a line but make it Tangent to the edge of the circular part and perpendicular to the sides of the slot.

Here is a link for more info on sketch constraints.

Are you changing the notch into a slot or is the slot a new feature that will exist with the notch?

close slot sketch.png

You could also use a 3-point arc (Start-End_Radius) and a coradial constraint.
coradial arc slot.png
Last edited:


Senior Member
What if the slot is on a circle? Do you still just draw it across? Or does it need to be the circumference?
So, if I understand your questions correctly, yes, you can just draw a line across the two points, it will cut everything that falls within the profile when using the extrude cut. (I'm assuming you already know, you'll need to do an extrude cut of the profile to actually get the slot to cut) Think of this profile like a die being used to cut a hole in a surface. If the die extends beyond the profile to cut, it just cuts air and doesn't affect the piece. However, if the die profile doesn't completely cover the surface to cut, it'll leave that piece behind. Same thing here. You're outlining the die profile to push through your solid.

Does that help things out or just muddy the water more?