Dang this thing is scary. I have to reproduce some crown molding to match the existing stuff in a remodel. It would cost bank to get it made so I'm making it myself and will get to keep the router bit which cost just under $100.

Using it with just the regular router base was sobering. That big chewer of flesh spinning at 23,000 rpm yielded gnarly vibration and I'm sure it's pretty well balanced. I had to make a new plate for that big hole but it's difficult to get the right result so I went with the quickie router table. Crude but effective. Has the bearing but I may put a fence on it for greater stability. I just screwed the plywood to the sawhorses. I keep longer machine screws in my router box so I can make such a table when needed. 10 x 24 IIRC.

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1986 300SDL, 362K
1984 300D, 138K

Routers can be scary. Especially that one.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

take small bites. A bit that size may need at least three passes.

Yup, on both counts. Holding the router in my hands was not fun. Both hands firmly on handles - for shutting off, place the top on the bench, hold firm with left hand to one handle, use other hand to flip switch. A couple of times, I was fumbling with the switch so I just reached over and yanked the cord, which fortunately was easy to do as it was plugged into a large power strip mounted sideways under my bench.

In hindsight, the best way to shut it off might be to lay it sideways on the floor, still running, let go and pull the plug.

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1986 300SDL, 362K
1984 300D, 138K

A guy on another site says I shouldn't run that bit at that RPM any faster than 15K or maybe only 13K. There's no spec. on the package but I should have checked their web site.

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1986 300SDL, 362K
1984 300D, 138K

I'm betting against it.

That's a huge piece of steel to be moving that fast. It would need very precise balancing (costly) for you to avoid feeling it at speed.

^ Coming from a guy who knows. Their website says 14K max speed. Oops. I almost made a large mistake. One that would have hurt. FWIW, I did the math and the outer edge of that bit is traveling at around 200 mph at that RPM, to put it in Joe-Bob terms.

I only ran the thing for a few minutes last night and that was enough. I'm going to shop for a variable speed device, several available for around $40 - $50.

I think though that if it were very far off balance, the thing would have shook my fillings out.

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1986 300SDL, 362K
1984 300D, 138K

I'm a bit surprised that you can get a proper finish if it is shaking that badly. I'd expect to see chatter on the material. It would be quite fine, however, due to the speed.

If the bit weight is eight ounces and the machining all over the piece results in a CG offset of only .001, you're still looking at nearly six lb. of rotating force at 20K..........way too much to manage.

That was my first though as well. You are way overspeed. My heavy porter cable 3.5 horse claimed has variable speed but is very heavy for hand held use.

At least it has slow start or it might twist right out of my hands with that heavy bit. I only usually use that router in a table. Actually you should have a shaper for making larger crown moulding.

I bet that thing would do a number on a bad case of roids.

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A shaper would be nice. I rarely need one and I only need 10.5 feet of this crown molding. It's hot huge - about 1 7/8 wide - 3/4 thick. Nobody makes it, that much is certain - the house is approx 80 years old. I inherited this job mid stream and God only knows what happened to the piece I'm replacing, wasn't saved, that's for certain.

I don't know what I was thinking that hand held would work at all with this one. Took major focus to control the thing and the results were poor in my brief test. The table test came out pretty smooth but at the very least I'm liable to beat the hell out of my router the way this thing is vibrating. I weighed the bit - it's a shade over 9 oz. The bearing and shaft are both 1/2" so I tried a crude balance check and it failed badly (see pics). I sharpie marked the end that hung down the first time and every test, the same side would hang down, not even close, and the edges on those two levels are not that sharp.

I ground a fair amount off of the wing part without the carbide to get it to behave balanced with just that crude test. Sorta surprising. Even at 14,000 that's a big bit, ought to be better out of the box than that. Didn't notice any difference with it back in the router though - I was hoping for a small improvement given how out of balance it was.

I probably should get a slower and stronger router. I'm guessing if I get a speed reducer box my Porter cable will lose a little of its 1 3/4 hp. A buddy on another site recommends a Porter Cable 7518. It's a tough one as I rarely need a 3 hp router.

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1986 300SDL, 362K
1984 300D, 138K

Maybe you can rent or borrow the machine you need.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

If time is not an issue, I'll balance the bit if you send it to me. Once balanced, you're problems with excessive speed will disappear.............just don't expect to change directions.

^ That's a generous offer. Time is not a major issue, and the speed control box would take at least a week to arrive. I could buy one locally (Woodcraft or Rockler store) but that would cost about $60 compared to $35 on Amazon. There are other more pressing issues to bring this job to a close.

I am wondering though if there might be other issues that are part of the factory recommendation of only 14K rpm. My neighbor at my shop is a metal fabricator, pretty knowledgeable on tools and he says it's very unlikely that the carbide bits would fly off. Would be an hellacious accident if they did, however. Then again, I'm not sure the vibration on this thing even at 14K would be acceptable.

Tom, I took your advice and called around. So far, the two rental routers I found are also 23K.

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1986 300SDL, 362K
1984 300D, 138K

There are some serious forces at work inside any rotating component that spins at high speeds. As an example, the large turbofan that you see at the front of a jet engine has about 38 blades. These blades, when rotating at 5,000 rpm will exert a force of over 3M lb. on the fan disc. Of course, in theory, the fan is perfectly balanced and the passengers never know that such forces exist, but be assured that every time the engine hits takoff speed, the disc must withstand 3M lb. trying to make it explode.

Your router bit is similar, but, of course the forces are less.

I'm quite sure the bit isn't designed with material properties and strength sufficient for 23K when the manufacturer limits the speed to 14K. The forces are nearly quadrupled at 23K and the bit might explode if there is any anomaly in the steel.

I could provide you with a perfectly balanced bit that will be perfectly smooth in the router...........but it can still kill you.