Motor surge with foot switch

[owler]

I recently bought scroll saw foot switch to use with my Dewalt. I have not experienced any problems when I use it. When I was watching my daughter scroll, I noticed that occasionally when she first stepped down the motor would rev higher than it should for a brief instant. I thought it was my imagination but it happened a few times.

She was scrolling with the speed control set pretty low. I thought maybe she was just lightly touching the switch but that does not make sense to me. Either the switch is engaged or it is not. Maybe it's not the switch at all.
Has anyone experieced a similar problem?

Dan

[arbarnhart]

Is the motor a capacitor start motor (does it have a bump on one side)? I don't know too much about variable speed induction motors, but on single speed motors, it needs the capacitor to "give it a swift kick" to get it started. It could be that the "kick" is swifter than a low speed motor setting. It's hard to explain, but the way induction motors work they keep the motion going in sync with the power cycles but aren't very good at starting motion. I have worked on motors with capacitor troubles that just hum and won't start and you can spin the motor by hand and it takes off. The odd thing is you can spin it in either direction and it will continue running in the same direction.

[jttheclockman]

Take the foot switch out of the loop and try it with the switch on the saw. Leave it at the same speed setting.

[owler]

I will take the foot switch off and try to recreate the problem at low speed. Maybe that's it. She was scrolling at much lower speeds than I ever do. I will let you know.

Dan

[owler]

I meant to post this sooner. I removed the foot switch and I had the same problem. It appears to be what Andy posted earlier about the capacitor giving the motor and extra "push" to get started.

This only happens at very low speeds and just for a brief moment. Something to keep in mind.

[William Young (SE BC)]

The motor on that saw does not have a capacitor start.
What you are experiencing is probably in the variable speed circuitry. The variable speed controllers gave problems with some of those saws but it is not limited to only your make of saw. The speed surging up and down on my DeWalt was one of the last things that started going on mine and I didn't want to replace that part as well as rebuild all the other worn out parts so I upgraded to heavier duty saw.
If your saw hasn't got a ton of hours on it like mine did, it might be worthwhile to replace the VS parts . I doubt if it will cure itself. Mine started like yours with it just noticeable at one speed but over time it started doing it at any speed.
W.Y.

[owler]

My saw does not have a lot of hours. I will keep on eye on it and replace it if necessary.

[minowevie]

I have to keep a close eye on this thread. My saw has done this from the beggining, or at lease for along time. I just got used to it, and keep in mind that when I start, and stop, and start again, sometimes it will just take off faster. Gee maybe I need a new saw. I sure wouldn't mind adding one to my family of tools. I sure Love my Hegner 18 , But I can love more than one. Lets see Excal 30 Or Hawk. mmmmmmmm tuff .Your friend Evie