Planning of Spare Parts

The only thing bean counters know is money. What you need to do is show them in black and red on paper, what the $$ cost is to carry spare parts for their production equipment, (in Black) and what the company will lose in $$$$ per hour, per day in equipment down time and lost production, (in Red). When they see for themselves the cost effectiveness of having spares and consumables in stock they wont have any arguments

Start with maintenance requirements, get numbers and reasons of occurring failures, factor in lead times and availability of spare parts and plan accordingly.

See also the various equipment manufacturers' recommendations for spares.

First identify which pieces of equipment are most critical to your company's operations and get the operation and maintenance manuals for them.