[AJD] Drilling and Tapping

[wb5cys]

There is a small sheet metal plate that bolts underneath my tractor to cover 
an opening which provides access to the flywheel.  The plate is bolted to 
cast iron with two 1/2" cap screws.  One of the holes is stripped and the 
bolt twisted off in the other.

How hard is it to drill and tap 50 year old cast iron?  I have no experience 
with drilling and tapping, does it require special tools?

Thanks!

Cal B.
Nacogdoches, Texas