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Old 15th Mar 2021, 12:23 pm   #1
Nanozeugma
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Join Date: Nov 2017
Location: London, UK. North Manchester now and then :)
Posts: 476
Default Enlarging an existing hole in a steel chassis.

Hi.
I have discovered to my irritation that one must assume nothing, lest one commits a faux-pas!
To explain...
I have purchased some new B9A ceramic valve bases to replace old, corroded ones, and (silly me) assumed the size of the drop through ceramic body would be the same diameter as the old one - wrong!
The chassis hole reads 18.85mm and the new valve base ceramic body 21.95mm. I reckon I need to enlarge the hole by 3.5mm.

I was wondering what would be the most appropriate tool to enlarge the hole neatly? I could, of course, use a half round file, but that would be a bit crude and possibly end up off centre to the existing holes for the fixing bolts.

Your thoughts much appreciated
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