hey ,
i recently installed xlr inputs in my rca ba-45/ba-43 rack units.
I used a 1/2" greenlee punch
available at your local hardware store (BTW:standard tool for electricians)
1/4" drill bit for a pilot hole
large round file
flat file
other helpful items include:
a sharp tool for marking
a steel straight edge or square.
Also don't under estimate the value of a sharpie (permanent marker) when marking the tiny little mounting holes . (your hard work will look like crap if it's not level and uniform)
I highly recommend that your purchase the xlr units you are going to use before starting.
my units had 3 tiny half-round notches at the 3 , 6 , and 9 o' clock positions and a large squard notch at the 12 o'clock position.
this is where the files come in handy
SO ..
1-mark and layout carefully
2-puch your center points with a punch awl (or a nail)
3-drill hole for your punch tool bolt (3/8 i think)
TIP:the round file can help with an off center hole drilled by, inserting the file in your drill and filing the hole till centered (use drill in forward and/or reverse for desired effect)
4-insert punch tool and tighten with a crecent wrench or a rachet
5-file in the round notches at the 3 6 9 positions with the round file
6-file the top notch with the square file at the edges, then with the round file across the top (to arch the line)
TIP: this area at the top must have enough room for your xlr locking release switch to operate freely.....even after they are screwed in tight.
7-finally the units should fit inside your holes now you can:
do some filing to adjust for centering and rotation
once you are satisfied
8- lay in youir units (maybe against a straight edge )
9-use the sharpie to mark your holes to fill entire exposed area!!
it will be impossible to mark the exact center of these holes since they are so small
10-remove the unit and drill your mounting holes
TIP: i cut off a self-tapping screw and used it for a screw bit (tightened into the chuck of my drill motor) they are small, sharp, cheap and made from very hard steel. (ALSO they son't break in half lik the other 3 cheap drill bits i had)
relace unit and proceed to mount
11- mounting options: go for exact holes and tap the threads with a screw.
be prepared with small nuts and bolts just in case.
BTW i used the punch and square file to mount my AC power too.
I'll be fixing these RCA units and posting some pics soon (hopfully)
well i hope this info is helpful
good luck
Toobie Snack