PCB pad/hole size advice

I am a rather novice amateur PCB designer. I have designed a PCB using
Protel 99 SE, using their standard library components and I am looking at
getting prototype PCBs manufactured. I now find that the libraries have
used numerous different hole and pad sizes, and that more different hole
sizes = increase cost! Further I find that some manufacturers use imperial
drill sizes and others metric.

So, I have two questions:
1. the libraries mainly use the following pad/hole sizes (in mil=1/1000th
inch)
pad=62, hole=28mil/0.7112mm = decoupling capacitors
pad=62, hole=32mil/0.8128mm = resistors
pad=50, hole=32mil/0.8128mm = dip packages
pad=62, hole=32mil/0.8128mm = vias

It would seem to me that I could reasonably use a single hole size for all
of the above. One supplier (Olimex) has standard drill sizes of 0.7mm
(27.6mil) and 0.9mm (35.4mil). Would using 0.9mm for all of the above
components be a sensible choice (finished hole size would be a little
smaller due to plating)?

What metric hole sizes would normally be used for such components.

2. I would prefer a design that I could send to whatever manufacturer can
offer the best price/delivery terms. This may not conistently be the same
company depending on circumstances during the life of the product. How can
I have a single design that can use either imperial or metric drill sizes
depending on the supplier? I don't want to have to have two different
design files, one imperial and one metric.


.

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