<brakes>caliper problem

Subject: <brakes>caliper problem
From: Joe Fahy <72510.1173@domain.elided>
Date: 11 Sep 96 11:47:08 EDT
<<There are two bolts that hold the calipers in place.  On my 1980 
528i, the head of one of the bolts on the passenger side rear is knocked 
off.  The rest of the bolt is still in the threads.  >>

	Greg, I have had success using left hand drill bits to backout sheared
bolts.  These bits are used in a reversible drill.  The counterclockwise torque
and heat from the drilling may remove the bolt.  You ca get (1/8", 3/16", 1/4")
from Eastwood part #1529 $3.99, #1527 $3.99, #1525 $7.99 or a set of all 3
#1519 $12.99  phone # 800.345.1178.  
	I have not looked to see what type of clearance problems you might run
into, but for this type of repair you probably will want to use a 90 deg drill.
The body of the drill is at a right angle to the drill bit.  This also lets you
see the part being drilled a little better.
	You may want to grind the end of the bolt flat if it is highly contoured
from the shearing.  Then centerpunch the bolt, this will make or break your
drilling success.  Note that there are self-centering centerpunches, these are
centerpunches that have a shank diameter to fit the hole and the centerpunch is
then spaced correctly for that diameter hole(wordy I know,sorry).
	When you drill it out you obviously want to stay in the center, to avoid
damaging the threads.  I would start with the 3/16" drill.  Usually you will not
have to drill the entire way through before the bolt starts to move.  I do not
know what is at the end of the bolt, but you probably do not want to drill into
it, so watch your depth.  Another trick I have used is the hand held impact
wrench.  Using the phillips head bit in the impact wrench to bite into the bolt,
use a hammer on the impact wrench.  This also can break the bolt loose.  You
could also try to cut a slot or cross into the bolt for a better fit for the
impact wrench bit.
	As always use your favorite thread lube WD-40 etc. to soak the bolt and
with the centerpunch rap the bolt to allow the lube to get into the threads.  I
would do this many times over the course of a day, prior to trying to drill.
	I have had less than desireable success using easy-outs.  As these
devices are hardened steel, if you break them off,I have, you will need the
services of a shop having EDM.  I have never used this machining technique.  I
all know about it is that it is a machine shop procedure, not an in situ
procedure.
	
<<I've been driving with it like this for a while - no problems. >>
	I think that driving with anything wrong with your brakes is too
dangerous, not only to yourself but to those who share road with you.

Is millersv.edu in PA?  I live in Centre County Spring Mills, PA  814.422.8210
if you want to talk about problem further.  That # is home & office with
answering machine so you can always get me.

Regards,

Joe Fahy
'88 ///M5
'74 911S