I've got some questions about router use. I've been using a Porter-Cable 691 router to cut some slots in 4x4 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 4x4 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 or to lossen parts stuck together. 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?
Bill, The PC 691 is a popular 1-3/4 peak HP model. I have a couple questions that may help you find a solution to your problem. First off: How much wood are you trying to remove in each pass? No more than 1/4" of depth per pass is a safe amount, this will help prevent overheating the motor and improve the accuracy of the cut. You say you start out with a 1/2" wide dado cut in your 4x4. I would suggest you widen the dado to 1" before making your final width cuts and sticking to the 1/4" rule. This means more passes but should improve the cut quality since the bit will only be making the final cut on one side. What type of wood are your 4x4's and how long are they? Are you giving your router and bit the chance to cool down between each 4x4? Once a bit has slipped in a collet there is a chance that either the bit and /or collet has sustained damage of some sort. A careful examination of each is in order. When installing the bit, do you insert it all the way and then back it out 1/8"? This is needed to allow the collet to properly grab and hold the bit. Your router should still be fine, but I would suggest taking it to a service center and having them go through it if you have concerns. And yes, your bit can be sharpened. Depending on what type of bit and which brand will answer if you are better off replacing it. Most often sharpening a bit will reduce the O.D. slightly. I hope this helps you get your project completed.
Bill, There are many fine routers that will do the job you are asking. As a rule the 2-1/4 HP routers will perform well for any type of routing. If you are planning on doing production work all day long, every day then the 3-1/4 HP models are called for. Remember that with the extra strength comes a great deal of extra weight. Here is the ideal situation: go to a store that carries different brands and get your hands on them. See how the adjustments are made, both right side up and upside down. This is to see how difficult adjustments are when the router is table mounted. If the router has a plunge base test and see how much pressure it takes to compress the springs and how the router returns to the "up" position. You are the only one who can decide which is best for you. Porter Cable 890 series routers are in the 2-1/4 HP catagory and very popular. DeWalt, Makita, Hitachi and Milwaukee have comparable models. Most of my routing is done with the Bosch 1617. If you elect to go with one of the 3+ HP models Porter Cable and Hitachi always get good reviews. I own a PC 7518 for the heavy duty work. Now this is my personal view and lots of people will disagree with this: Most of the failures we see reported are problems with the "soft start, speed controller models." A built in speed controller adds $20-30 to the purchase price, but when they break get ready to shell out over $100 to replace it. An aftermarket speed controller box will run you maybe $40 or less. These units are larger and nobody has reported one failing yet that I have seen. Because of these facts I prefer the idea of buying a router with a normal on-off switch. A speed controller is mostly needed when using larger, heavier bits. (Over 3" diameter) Go through the posts and see recommendations from other forum members, and good luck!
Here's a old timer trick, take a spade bit and remove most of the wood and then use the router to clean up the slot..
This will take most of the load off the router and the spade bits are cheap unlike a router.
You have posed your question to some of the sharpest wood workers in the nation, so there are a lot of viable solutions to your situation. I had not thought of using a spade bit as BJ suggested.
If you are concerned about your PC 691, I used to work on construction equipment and can give you a few things to look for. Remove, clean, and check your collet and nut. Automotive brake cleaner works great for this. Look for signs of wear and micro splits or cracks. A good strong light and a magnifying glass are recommended.
Used compressed air and blow out your motor assembly. If you feel comfortable enough with your repair skills, disassemble the motor to do a visual check of the armature and windings. Bubbling, burned, or discolored insulation means the unit has been overworked and may need to be replaced soon. There is usually an acidic smell that goes along with the burned insulation. As long as you have it apart, check the bearings for wear or discoloration.
There are test machines at tool repair centers that can tell you exactly how much damage may have been done. It can verify shorts, opens, and broken grounds.
I hope this gives you a little direction on the PC 691.
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