Bob,
I know we all do things, which would be best done by someone better equipped. It may be due “lack of funds, “time” inconvenience and list goes on. I’m as guilty as anyone. For that reason I thought about not responding. But decided to log back on and add my two cents. Thought I might be a little more knowledgeable in this area. I have over 35 yrs experience as a research machinist, tool and die maker and Metal Trades Instructor. I earned BS degrees in Precision Machining and in Construction Technology/ Home building. My Master’s is in education.
While most of what has been said is true; I think you need to really think about this.
Lets just look at a few facts.
1. A router is not made to cut any type metal. RPM’s are way, way too high. ( The highest RPM on any of my Milling machines is less than my router’s lowest RPM).
2. A router bit is made for Wood. The angles (relief, Back.etc) are totally different than on an end mill.
3. True, there are carbide router bits, but the angles are still for wood. An end mill can be used in a router to cut wood, but the finish is not as good. They weren’t made to be interchanged. You just can’t get a router set to the correct RPM. I won’t even get into feed rates.
4. Any small machine shop that has Bridgeport mill or similar clone; can setup and mill the slot in less than ½ hour. That’s about $50.00 around here. It is correct that a big shop will charge for stopping their line. Add another 200 plus for that. But there are lots of little shops that would be glad to get the work. Find one that likes woodworking and I bet he/she will do it for less.
5. I looked at my craftsman table saws they have cast iron tables, but I do understand some models do use other metals.
If you do decide to try it. Here a few more things to consider!
1. You will need a sturdy jig, the forces will be a lot higher than wood.
2. If there is steel anywhere in the cutter path. (bolts, trash in the casting, anything) You gonna wish you were on another planet. If you survive it, plan on buying a new router.
3. The chips, that get everywhere, are over 500 degrees, so be ready not to jump flinch or react when they go in your ears, hair, arms and they love a shirt collar.
4. Finish is also dependent on a lot of factors, one is feed. I haven’t met anyone yet, that can hand feed as constant as a machine. T-slots on expensive TS are hand scraped, to remove cutting marks left by machines. What about coolant? Do you have the kind made for aluminum?
5. Lastly the bearing in a router is not made for this, so there will be vibrations, this will also cause a very rough finish.
Just about everyone on this forum talks about safety. It should be the first thing we think about when we plan a project. I don’t like telling anyone not to do something they feel is necessary. But at less think this though before you start on it.
BE SAFE; BECAREFUL
Sorry this is so long!
Harry