Agraffe Trouble

[PNOTNR@AOL.COM]

List, 

I have a piano in my shop about ready to be restrung.  The plate is out of 
the piano and I'm replacing the agraffes.  Two original agraffes broke in the 
process of removal, likely due to something that had been spilled onto the 
plate and froze them in place  a few years back.  

Drilling down the center with a 1/8' bit, and turning with an EZ out worked 
on one.   I tried drilling out the rest of the other agraffe with 
progressively larger bits, stopping short of 7/32".  I hoped that the bit 
would follow the brass, and not bugger up the iron plate.  

Opps!!  Stripped the threads in the plate.

So now I need to plug and tap the hole.  Any hints?  Not having done this 
before, I'm wondering if it is a fairly straight forward procedure, or is 
there someone I should have do this for me.  

They say if you aren't making mistakes, you aren't learning, right!?

Guess I'm learning.

Humbly,

Gordon Large, RPT
Mt. Vernon, ME