Hi,

 I’ve got some questions about router use.

I’ve been using a Porter-Cable 691 router to cut some slots in 4×4 posts.
the bit is 1 in in diameter and has a 1/2 in shank. I’m cutting 1 1/2 in

wide by 1 in deep slots across the 4×4 posts. To make the routing more

manageable I made a template and also made a 1/2 in wide dado cut down

the middle of the slot to get it started. I make the final cut down both

sides of the slot with the router.

My problem is that after about 20 slots the chuck and bit were so hot

that the chuck let go of the bit dropping the bit into the work and

making a nasty jam and damaging the work. All my expert friends ( a

contractor, a carpenter, and the store where I bought the router ) have

all said to me, “That’s not right you should get a new chuck. There must

be something wrong with the one you have.”

I think they are wrong. I know how heat is used to assemble gears on

shafts etc. in mechanical systems. I think that when the chuck gets hot

enough it is just going to let go. Even though it was loose when the jam

occured it tightened back up when it cooled to the original tightness and

could not be tightened more.

What is your opinion on this subject?

I would think that good design practice would require that the tool

contain a thermal overload switch that would stop the tool before it got

too hot, but I was not able to find any indication of that in the manual.

My next question has to do with the router that has been subjected to

this overheating. Is it still safe to use? How can I determine if the

motor has been damaged?

A contributing factor may have been a bit that was getting dull. It

seemed to be sharp to the touch but the “push” necessary to make a cut

was going up. Is that the only way to judge?  Can the bit be sharpened?

If you are willing to go to the trouble of replying please also email me at [email protected]