This customizable star knob has curves in all the right places. I should know because I spent a lot of time calculating them. The number of points on the star and all other dimensions(listed in "Customizer Notes" section) are fully customizable allowing for a wide variety of shapes and configurations.
Knob may have a either a hex cap bolt, hex nut, or round shaft press fit into it. For round shaft (no bolt head or nut) set either boltHeadThickness or boltHeadDiameter to zero.
The Thingiverse customizer has an issue where some parts of the knob preview as transparent, but if you click "Create Thing", the resulting model should not have any such holes in it. Changing the angle can help if the transparencies make visualizing difficult.
Example STL fits M8 hex head bolt.
Enjoy and please post any makes you do.
The knob profile(as seen from above) is a curve made from alternating inward and outward facing circular arcs, formed by adjacent circles which are tangent to each other.
Here some of the parameters affecting the handle shape are illustrated. Handle Inner Diameter(blue circle), Outer Diameter(green circle). and Point Radius(red). Changing the Inner Diameter can drastically affect the shape of the knob handle. Inner Diameter values that are close to the Outer Diameter will create flatter sides, while smaller values will make the knob more and more curvy. Stars with more points may require smaller Point Radius, and Larger Inner Diameter to avoid overlapping or missing sections.
// Number of points on the star
points = 3; // [3:20]
// Diameter of the outermost tip of knob handle
handleOuterDiameter = 75;
// Diameter of the innermost indent in the knob handle. This affects the profile of the curve around the edge of the knob. Values closer to outer diameter will create less curved profile,
handleInnerDiameter = 30;
// Radius of the star points
pointRadius = 10;
// Vertical thickness of knob handle
handleThickness = 15;
// Radius of top fillet, forms rounded edge all around top of handle
rTopFillet = 10;
// Radius of bottom fillet, forms rounded edge all around bottom of handle
rBottomFillet = 2;
// Diameter of the base, this comprises the mating surface when knob is tightended
baseDiameter = 20;
// Distance from bottom of knob base to underside of handle
baseHeight = 15;
// Radius of fillet between handle and base of knob
rTransitionFillet = 10;
// Diameter of bolt hole. Fits bolt shank, or plain round shaft.
boltDiameter = 8.4;
// Diameter of bolt head. Size across flats (wrench size). Set to zero if no head (shaft hole only).
boltHeadDiameter = 13;
// Thickness of the bolt head (or nut). Set to zero if no head (shaft hole only).
boltHeadThickness = 5.5;
// Distance from base of knob to bottom of bolt head (how much thread is inside of knob)
boltHeadHeight = 5;
// Number of sides on bolt head (or nut) (6 for hex head bolt, 4 for carriage bolt, for example)
boltHeadSides = 6;
// Diameter of counterbore, which the bolt head should fit freely inside. If 0 then a default hex-head counterbore will be automatically calculated as (boltHeadDiameter * 2/sqrt(3) + 1)
boltCounterboreDiameter = 0;
// Radius of rounded edge at top of counterbore
rCounterboreFillet = 2;
// Resolution in mm. This model can take a long time to generate, especially at high detail. To keep things responsive use a coarse (higher numeric value) resolution while making changes, then change to a finer setting just before clicking "Create Thing" and generating the model.
resolution = 0.75; // [0.2:0.05:5]