Router speed controls - am I missing something. . . .

[Cary Lane]

I just finished getting my BenchDog Pro-Max wing installed on my table saw. In it I have placed a 3.25hp Freud router. I picked up the router at an auction for $10, non-working, upon being told it was an "easy fix." Well the speed control module was bad, so on advice from SMC and other router forums, I wired around the speed controller.

It runs like a champ. I fabbed up a bracket to mount an MLCS heavy duty universal speed control knob so I could restore VS function. I wanted to put a couple RPM marks along the face of the MLCS dial, so I have borrowed first a GenRad Strobotac from work and then a Shimpo non-contact tachometer (simpler to use, but not as fun, or seizure inducing :p) to get some measurements to make my scale.

Now the problem. The router cranks to about 24k full bore. There appears to be no change in speed from about 1/4 dial travel all the way up to max. Below 1/4 travel there's not much drop off in speed (about 6k rpm at the most) before the motor stops.

Has anyone experienced similar behavior with their router speed controls? Or do you notice a nice linear speed reduction along the dial? Is this a symptom of a cheap switch? I notice the scale on the side of the router gives several nice little ranges for their settings, ranging down to about 10k (I don't remember off the top of my head). What is the slowest speed I'd ever run? Is it around 10k with a large diameter panel-raising bit?

I realize most probably just "go by ear" and I've overkilled this thing, but I do like to tinker.

Thanks -

Cary

[Tony Shea]

That is actually fairly common with speed controls and dimmers. I'm not up on my electronics but know it has something to do with resistances not matching up with the initial speed controls inside the router. Maybe someone else can be of more help. I just know that this is common with cheaper light dimmers and speed controls.

[Rod Sheridan]

Hi Cary, for true variable speed on a universal motor, you need a feedback signal (consider it a tachometer signal) from the motor to the speed control.

That way as the motor speed drops, the speed controller can advance the circuit firing to provide more current to keep speed constant.

If you just use a lamp dimmer type control (no motor feedback) the motor speed will change greatly with load.

That's what you're experiencing, no load on the motor so it's capable of running at full speed at almost any setting on the dimmer.

Try setting the dimmer at 25% and making a shallow cut, you'll see the speed drop.

I would suggest that you buy the internal speed control module for your router.....Rod.

[Cary Lane]

Thanks for your responses, Tony and Rod. I kinda wondered if the no load condition had anything to do with it. I haven't made a test cut as you suggested, Rod. And if I'd gotten the original speed controller, then I'd have a fair bit more than $45 invested. I think the setup I have now will suit me just fine until another screaming deal comes around. :D