Porter Cable 690 depth slippage

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
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"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
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.
Tom
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I put the o-ring all the way up on the shaft of the bit. The tip of the collet butts against the o-ring. For the most used bits, get an o- ring for each bit.
I have an old Craftsman router that had similar tightening problems. A good yearly cleaning prevents this problem.
Sonny
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You might google this. I recall someone having a kit that fixed this, but I'm not sure if it was this model. Maybe someone else here will remember.
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snipped-for-privacy@cfl.rr.com says...

I presume that's the plunge base. You might want to consider shelling out 50 bucks or so to get the fixed base.
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Actually, it sounds like the fixed base. The older models used a thumbscrew to tighten the base to the body. The newer models have a clamp.
scott
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Get a new replacement collet. That worked for me. Any accredited service shop should be able to order one for you (or two, if you use both 1/4" & 1/2" collets) .
Amazon has them too: (Amazon.com product link shortened)
Luigi
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The old pliers trick worked for me.
Disassemble screw and nut, clean and reassemble with anti-seize compound.
Lew
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Luigi
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Lock levers as seen at the 310 link, ( http://patwarner.com/pc310_special.html ), a dime a dozen, will lock up that motor. Reid tool & mcmaster.com *******************************************************

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"routerman" wrote in message
Lock levers as seen at the 310 link, ( http://patwarner.com/pc310_special.html ), a dime a dozen, will lock up that motor. Reid tool & mcmaster.com *******************************************************
Excellent!
Tom
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Thanks to all for your inputs.
I do not use a plunge router for dovetails. Is there something I am missing?
I re-visited the clamping mechanism on the PC 690. The head of the clamping bolt has a square nut at the end which is offset on the bolt shank. Ideally, this square head should lock itself into the boss on the base. I noticed that even under full clamping pressure, the bolt can move slightly within the boss. I placed a lock-washer under the square head, and this appears to provide a measure of security. Time will tell.
It is possible that I had additional problems with the bit slipping in the collet. I purchased a new collet and bit, and still experienced the same problem. Please note that the original collet and bits are used in the router table WITHOUT any problems. It is possible that I need to exert more pressure when I install the bit(s) on the portable router.
Again, thanks for your inputs/advice. Much appreciated.
John
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"John" wrote in message
Thanks to all for your inputs.
I do not use a plunge router for dovetails. Is there something I am missing?
I re-visited the clamping mechanism on the PC 690. The head of the clamping bolt has a square nut at the end which is offset on the bolt shank. Ideally, this square head should lock itself into the boss on the base. I noticed that even under full clamping pressure, the bolt can move slightly within the boss. I placed a lock-washer under the square head, and this appears to provide a measure of security. Time will tell.
It is possible that I had additional problems with the bit slipping in the collet. I purchased a new collet and bit, and still experienced the same problem. Please note that the original collet and bits are used in the router table WITHOUT any problems. It is possible that I need to exert more pressure when I install the bit(s) on the portable router.
Again, thanks for your inputs/advice. Much appreciated.
John
The lock washer will probably work for a time but lock washers are designed to work one time. Each time you use it after that you are going to have less than stellar results. Swingman puts a pair of pliers on his to tighten the thumb screw. I suspect with time the design wears out.
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