Fair point Mr Smikle, I imagine the only thing they would need to change often might be, say, the aero cover mounting diameters if they changed the aero cover design, which I imagine would have settled down now. But can you imagine how many re-design's they must have had when they first introduced those covers? they surely would have struggled getting the assemblies on and off to begin with, or struggled to reach the locking pin in a hurry, or required more or less cooling. There would have been frantic purchase orders flying back and forth, threats and angry telephone calls, good grief, I've been on both sides of this particular war of words.
When anyone from Tier 1 (F1, NASCAR) or Tier 2 (DTM, WRC, LMS etc) orders a part from a subbie they will never make any extras other than the minimum scrappage allowance, even if they are a very regular and loyal customer. So many companies will have been burnt in this way, a slight re-design and everything you hold is worthless, the designers and buyers from the teams have the best of intentions of course, they are trying to reduce costs by getting a larger quantity made and being doubly clever by getting you to hold half the order at your expense but when the order comes for a new design they sure can leave you hanging with a few thousand £/$ worth of stock.
It's not unknown for a team to ask that work commence on a verbal agreement since waiting for a P/O to be raised can add too much to the lead time and then you can find yourself in a bit of a dilemma. An example would be:
Team: Get started with 200 off, just machine the Taper the hex and the thread, we will get back to you with a P/O for the correct part number when we know shoulder length and diameter for the aero cover groove.
Nut Contractor: makes 200 off
Team: Right here's a P/O to finish 100 off to this design (included), hold onto the rest as we are working on a slight variation, we will get you the P/O for the rest in a few weeks.
Contractor: chases team for order and is eventually told they needed a major re-design and the stock is scrap.
At this point 2 things can happen:
1. Some haggling over money already spent, several hours wasted working out the cost of work to date which by now is almost outweighed by the extra time taken to resolve, and if you are lucky, an the guy placing the order has a heart, you get paid for the machining work already done.
2: Where is the purchase order? you shouldn't have begun work on those part's as you didn't have a completed order from us. Payment denied!
This is an extreme case but when it has happened once, as it surely will when companies are trying to help a customer out, it changes the way orders are dealt with and when quoting a new job, covering one's arse is as important as an accurate representation of cost.
God what an essay, sorry
