Hi @slugbut Wellcome to the Forum.
Use Sketch > Line/Arc to create an Arc, alternatively use Sketch > Spline.
In the following Add > Construction Plane > choose Option - Perpendicular to a Curve.
Tap on the Curve [Arc in this case] at this stage the Construction Plane can be dragged along the Curve.
When there are sufficient Construction Planes choose one at the end of the Arc and Tap on it with a Finger.
This will move the Construction Plane and display a Grid ready to accept a Sketch.
In this case Circles were used.
Hiding Construction Planes and their Sketches, will improve access to the Plane Sketch in progress.
Sizing the circles appropriately can provide the shape required.
Tools > Color was used to make the ‘tooth’ transparent to show the construction:
Set up your Design Scale appropriately [I quickly drew this without paying attention to Scale]
This may offer some more help:
https://discourse.shapr3d.com/t/combine-loft-and-sweep-tool/5988
Shout if you need more help.
Happy S3Ding.