If you do not have it already you may find Karen Cheng's fantastic book Designing Type very helpful. It is always useful for things like this to look at what others have done and fonts like Cambria, Georgia or Verdana might be good places to start looking.

With regard to mathematical typography and typesetting I would highly recommend the Mathematical Typesetting booklet edited by Ross Mills and John Hudson and I daresay that John may be able to recommend other sources and further reading on the subject if he sees this.

With regard to your initial question, in my (extremely limited) experience they tend to be but others here will no doubt have much more informed opinions.

I prefer putting all the dashes at the same height, just a bit higher than the middle of the x-height.

By "figure height" do you mean numeral height? If so, that's not a post, that's a book! :-)

hhp

Also is figure height same as x-height

No, figure height is the height of the figures...

Old style figures are often slightly taller (not counting ascenders) than the x-height. Sometimes they follow the small cap height.

No, figure height is the height of the figures

Oh thought so but was not sure... Thanks

It makes sense to align the hyphen and dashes, and for common text use they should normally be slightly above centred on the x-height. In all-caps settings they need to be raised to be slightly above the centre of the cap height; this is why many OpenType fonts contain 'case' feature variants of the hyphens and dashes.

Mathematics is a different beast altogether. There is a central horizontal axis running through each line of an equation, normally centred on the (lining) numeral height, to which operators are aligned.

In all-caps settings they need to be raised to be slightly above the centre of the cap height

I would say slightly below.

hhp

and what about the thickness of these dashes(Not width but the height)? Should the hyphen be thicker than the en/em/minus ?

Hyphen/En/Em same everything except length (with the Em optionally having negative sidebearings, although I myself don't do that). But the Minus is a special case.

hhp

Hyphen/En/Em same everything except length

Not necessarily. In my current project for example these get thinner as they get longer, and I know I'm not the only one.

Sure, I was just saying what I prefer doing. In fact I'm the "rules are meant to be broken" type. :-)

hhp

I would say slightly below.

Well, if you want the hyphen and dashes in all-caps settings to appear below the centre line, you could do that, but why would you want to, especially when those caps typically have waist features such as the bar of the H and the middle of the B above the centre line? Indeed, the easiest and least visually disruptive way to position the hyphen/dash height in all caps settings is to align it to the H bar.

Regarding weight, I usually have the en dash and em dash of the same thickness, but the hypen is considerably heavier.

Now, who here provides kerning for dashes so that they overlap when typed in sequence? This supports their use in bibliographical entries, where a sequence of joined em dashes is conventionally used to replace repeated author citations, e.g.

Furtzwangler, J. Water polo my way. Harvard University Press, Cambridge MA. 1982.

———————— More water polo my way. Privately published. 2005.

———————— The Furtzwangler way to better water polo. Wetwings Publishing. San Antonio TX. 2008.

who here provides kerning for dashes so that they overlap when typed in sequence?

That's what I do to the Em dash (and sometimes the underscore).

hhp

yes, me too. Since I have been asked to provide em-dashes performing a continuous line when set in a sequence, I apply kerning to it.

Now, who here provides kerning for dashes so that they overlap when typed in sequence?

I don’t claim to be an innovator, but when I chose to do this with Whitman in 2003, I had never encountered this pair in any other fonts that I’d investigated. True, the practice of adding sidebearings to the em dash was also not as widespread as it is today.

BTW, John, the typical convention in the sort of bibliographic example you show is only a three-em dash — not eight!

Of course people can innovate independently: the first time I did that was in 2001. And/but I have to suspect others had done it way before.

hhp

When a continuous-line appearance is needed several times in an InDesign document, I create a character style for it that has tight kerning. Makes it easy to adjust the spacing of all occurrances later, if needed, plus you can temporarily make that style a different color so you can immediately see if you've applied that style to some text or not.

Also works for underlines used to make rules on a form (although I normally prefer to create rules by a different method).

Problem is those overlaps show on screen. For webfonts, this solution is not good enough.