I missed this thread when it got started, and will chime in now.
Segments - there is a
multiplicity of
TYPES of
segments, and therefore under the name of "Segments", Curly is exactly right.
1.
Herringbone is a type of segment that is different from all others. No standards needed except all parts (in general) should be the same size. Herringbone can be 180° or 360°. Here is a 360:
https://www.penturners.org/resources/360-herringbone.3/
2.
Freestyle 1 in which a bandsaw is used to cut
wandering/udulating designs with a thin strip of metal or contrasting wood between the parts. Thickness of the fill in segment up to the maker and within the realm of feasibility.
3.
Knots in which the fill in material must be precisely the width of the saw blade's kerf
4.
Stripes - fill in material the thickness of the kerf, or if a professional, the precise angle of the cuts, or if made up in a blank by adding layers. In some cases the complexity is in the precise entrance and exit of the drilling. example of stripe:
https://www.penturners.org/media/imported-photo-from-leehljp.3500/
5.
Round segments - what ever thickness you want. See this one as an example:
https://www.penturners.org/media/imported-photo-from-leehljp.3506/
6.
FreeStyle 2: none standard shapes - designs combined for effect - the sky is the limit in design. Here is a thread on Kaos, non standard, bowls - not pens, but pens can be made similarly.:
https://www.penturners.org/threads/more-segmented-kaos.168883/#post-2109276
7.
Dots can be included as segments, IMO. No size limit, but the angle can be very important: see this thread:
https://www.penturners.org/threads/on-center-segmenting-drilling.168993/#post-2110654
I am probably missing a type of segment or two, and if there are other types, please add them and a pict or link if you have one.