Thread: Dewalt 740 radial arm saw

John,
The amp rating of the breaker has no impact on the problem you are experiencing.

The saw is plugged into a 15 amp outlet along with the lights

Are the lights physically plugged into the same outlet? Or are they on the same circuit? Normally there is only one 15A outlet on a circuit (and no other outlets, appliances, etc).

John, the 740 uses a single phase induction motor. These things will not start without without either mechanical assistance to establish rotation and direction, or the temporary assistance of a start winding.

Because you managed to stall the motor, it needs either of the above to re-establish rotation. By reversing the feed to clear the work, you have wound the motor backwards and established some level of reverse rotation. Once the jam creating the stall has been released the motor is free to run in whatever direction of rotation you have established, in this case reverse.

In theory, once the motor has stalled, the start winding should activate to restart the motor in the required direction, but I suspect that the torque supplied by the start winding was less than that supplied by reversing the feed, so the reverse feed has won out.

With regard to the power situation, the saw shouldn't cause significant voltage drops in a 15A circuit when starting, so I suspect that you might have some mechanical load being applied to the motor, or the power supply to the workshop is inadequate in some way.

Thanks for the replies.. thr plug where the saw is plugged into is on the same circuit as the lights with a 15 amp breaker. The lights are not plugged in with the saw...
So there is nothing wrong withe the saw? I guess I'll just have to watch & make sure not to stall it again.. I have since changed the blade, & it saws faster & much better now, & stalling doesn't happen, but of course I still watch the feed rate & make sure I pull the saw slower when cutting..
Would all saws react the same way if stalled, & maybe run in reverse?? I mean all brands, or is this unique to the Dewalt?? Would I be better off selling this one, & getting maybe a Craftsman or ??
John

Anything with a single phase induction motor can do it, as its a function of the motor type. Three phase motors have the direction of rotation set by the power phase sequence and connections between the windings and power source, so they won't do it. Universal motors (AC/DC brush motors as per circ saws, hand drills, angle grinders etc) wont do it as the are self starting as well.

Have you checked the allignment and setup on the saw at all. If the blade doesn't track exactly parallel with the arm, you develop an increasing side load on the blade as you feed the head through the cut. While the blade will try to work through that, it will give a rougher cut and contribute to stalling. Normally caused by the head pivot being out a little, but can also be caused by the rollers in the head carrier on the arm as two are fixed and two have some adjustment for load and drag.

Seems like it might be a bit to do with the blade as well, if replacing it has helped big time.

Originally Posted by malb

Anything with a single phase induction motor can do it, as its a function of the motor type. Three phase motors have the direction of rotation set by the power phase sequence and connections between the windings and power source, so they won't do it. Universal motors (AC/DC brush motors as per circ saws, hand drills, angle grinders etc) wont do it as the are self starting as well.

Have you checked the allignment and setup on the saw at all. If the blade doesn't track exactly parallel with the arm, you develop an increasing side load on the blade as you feed the head through the cut. While the blade will try to work through that, it will give a rougher cut and contribute to stalling. Normally caused by the head pivot being out a little, but can also be caused by the rollers in the head carrier on the arm as two are fixed and two have some adjustment for load and drag.

Seems like it might be a bit to do with the blade as well, if replacing it has helped big time.

thanks for the reply, no I haven't checked the alignment & setup as such, only checked to see if the cut was square on the board I cut.. I never got a manual when I bought this saw several years ago.. Where can I get instructions in setting it up, & setting the saw right in relation to the arm??