Hi there Dave, I know what you are talking about here. I do know that a Dado-cutter, will not work properly, if there is a brake on the blade. A Dado cutter has two blades, one for each side of the dado. Am I wrong Dave?. We use what is called a "Drop Saw" here in NZ on Construction sites for the cutting of timber and all of them have a brake on them. Now, as far as I'm aware, they have a Universal(Series) motor driving them, the larger sizes do have an Induction motor. What causes the braking in the Series motor is that when the trigger is released, the Back EMF of the motor is used to stop it. The Induction type use a system of DC injection to effect the slowing of the motor.
Re: Electric brakes#142889 03/13/0511:15 AM03/13/0511:15 AM
You are right about the dado. It has 2 blades, one on either side and four chippers in the middle.
I can't imagine what effect the brake has on this. The only thing I can think is it loosens itself when the brake is applied or the torque created due to the weight of the cutters might damage the arbor of the motor.
The saw in question is a Makita 5903R. Does this mean anything to you?
I'm almost sure it's a series motor. So can the wiring be altered to disable the brake?
Re: Electric brakes#142890 03/13/0511:41 AM03/13/0511:41 AM
Dave, All I can say at this stage is who is the manufacturer of the dado blade?. Also have you contacted Makita to see if this sort of modification is even safe?. Reason I say that Dave is because if you disable the electric braking system, you could also be disabling any sort of speed controls too. The speed and stop systems could be controlled by the same Triac/Diac or SCR's. To have an out of control Series motor would be very dangerous.
Re: Electric brakes#142891 03/13/0512:00 PM03/13/0512:00 PM
Oddly enough Dave I have the Service Manual for that saw here. I just found it in my pile of Manuals that I have here. According to the manual, it has a Series motor and it should not be used for anything other than a Circular saw. My advice would be to buy a dedicated Dado cutter.
Re: Electric brakes#142892 03/13/0512:52 PM03/13/0512:52 PM
Taking your advice I'm going to look for a different model saw, older probably, and forget about modifying the one I have.
Makita would say not to use the saw for anything than what it's designed for. However, I see the Americans doing this sort of mod all the time because a dedicated dado machine runs to around £3000 which, for me, a simple carpenter, is just out of the question.
If I ever do get round to this then I'll make sure it's as safe as can be made, substantial guards etc.
Re: Electric brakes#142893 03/13/0504:23 PM03/13/0504:23 PM
There is no speed control as such, just a simple on / off trigger. So, would it be dangerous to disable the brake? Obviously it would be more dangerous because the blade kept spinning after the trigger was released but what about this thing with the motor running out of control? I've got a picture in my mind of it accelerating out of control til it just disintegrates :-)
I'm glad you agree with me on the Health and Safety thing. They have made a big difference on the larger sites for the better. I can see this when I go to some small domestic extension and see how crazy the the way they are working is. Just seems to me that they starting to go that bit too far, too silly, so losing the respect of the blokes and spoiling what should be a good thing