"John" wrote in message
My PC 690 is over 10 years old and has served me well. I have been
dovetailing several new drawers and am having problems maintaining the depth
adjustment. It appears the locking nut that is supposed to lock the motor to
the base will loosen and allow the bit to drop. Not good !!!
Searching the internet has provide me with one other woodworker who
experience the same problem. His solution was to use pliers to tighten the
nut/thumbscrew. Eventually, this will weaken the aluminum housing, again not
good!!! There must be a better way to solve this problem. Dovetailing
requires constant accuracy 100% of the time.
John, I've got that same router.
First, make sure the thumbscrew threads, both male and female, are good and
clean, and lube them lightly with just a touch of machine oil or even WD40.
Then lube the mating face under the thumbscrew with something heavier like
synthetic white grease. This will make sure that the thumbscrew will go all
the way tight and not hang up as you tighten it. An alternative would be to
use anti-seizing compound on the threads, which would ease the tightening a
bit without actually lubricating them.
I take the body out of the base and clean it and the inside of the base with
a 3M pad to make sure that it's good and clean, and lube it as well with
light machine oil.
After a good clean-up like that I can usually hand-tighten the thumbscrew
and it'll hold just fine. But just to be sure when I'm going to be doing
something like dovetails I take a small pair of pliers and give it just a
little bit more - less than an eighth of a turn. That hasn't done any
noticeable harm to the housing in the fifteen years or so that I've had the
router, although it's pretty lightly used (no production work).
Be sure that it's not the collet that's slipping. That'll show you the same
symptoms. Clean the collet - both the inside and the threads - and the shaft
of the router bit really well, lube the collet threads and the nut as above,
and when you tighten up the collet make sure that the shaft is just a little
bit clear of the bottom before you start to tighten it. Some people put a
tiny o-ring in the bottom of the collet to hold the shaft clear.
I don't seem to have problems when I use these procedures, unless I just
fail to crank it down as far as it'll go by hand. Watching the router drop
out of the base and sit there running under a router table makes you real
thoughtful there for a minute.
You also might consider getting one of the newer bases with the cam-over
lever that locks the router into the base. I'm tempted by that myself but
haven't pursued it.