Well, it all depends on time and place.
For example, if you are the lone armourer at a castle, you would be in charge of everything.
If you were in one of those rare abberations called "cities" things could get quite specialized, but even then you had one guy coordinating the material to make sure it all fit together.
Making a shield is pretty easy -- I've seen people with a bit of training put together a war-quality wooden shield (complete with metal boss and rim) in 3-4 hours (a little bit longer if you want the double-layer wood set at a cross level of shiled).
Helms depend on style, of course, but a simple nasal helm can be pounded out in a few hours; a full Jousting Helm that attaches to your plate armour can take days.
Armour can get tricky. Armour is very, very individual. Sure a suit of Padded, Leather, or Studded Leather can be made in rough "sizes" and mass produced, but believe me you do NOT want chainmail that is not fitted specifically to you (and articulated plate even more so). Chainmail is not a fast process at all -- winding all those links and then essentially "knitting" them takes LOTS of time -- even longer if you are talking about rivetted mail. If you have someone who is fast at this (probably someone who already has 1000s of links in pre-set swatches) you can get a good hauberk inside of a week, but usually plan on much more time. Full Plate? Better expect 2-4 weeks, maybe more, depending on requirements, availablity for fittings, how well articulated you want it and the like.
Well, there are some rough scales for you -- it's a place to start at least.
(Oh, most of these answers come from a friend of mine who is a professional armourer -- one of the few people who actaully makes a living off catering to the SCA.)