[ROVERNET - UK] Drain plugs & spanners
gofanu at usachoice.net
Tue Mar 27 20:13:58 BST 2007
The plug is actually 7/16W/1/2BSF, which is in theory .007" larger than
13/16.; Given normal tolerances, 13/16 will be a nice snug fit - very
good on the brass plug that welds itself in! Standard 6 point spark plug
sockets are near perfect. A typical good quality 13/16 willl be about
.008 over nominal, and a crappy one might be .015 over. You will need to
take a file and gently dress off any burrs from earlier gorilla-fisted
abuse - keep all filing square and parallel! On this shallow and soft
head, it is very wise to find the tightest fitting spanner possible, and
then grind the end flat so that the chamfer is nearly gone; the chamfer
can easily amount to 1/3 or more of the head depth of the plug. As a
fine but worthwhile point:
Most good quality recent (last 25 yrs) boxes/sockets are "Flank drive"
(Snap-on ^(TM), I think), which means that inside corners are relieved
(no sharp internal corners) so that they don't touch the fastener. The
"flats" are also skewed, as if it's already worn out. Some don't have
"flats", but a rounded profile. These are far superior and more
forgiving of corner boo-boos, and they don't cause them either.
I can send folk another short treatise on Britbolts, spanners, and how
to easily make Brit spanners out of common ones. Email, subject: Britbolts.
DO NOT even THINK about open ends, adjustables, pipe spanners, or pliers
of any kind - those are for beating people, and grabbing nuts of those
who use them on beautiful and delicate parts!
Use the back corner plug, since you can tilt the car a bit to get it to
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