On Wednesday, June 01, 2011 07:08:02 PM Dave did opine: > Gene, > > You were very lucky. > That's the way I read it. ;)
> Read this link down the page a bit... > http://woodworking.com/forum/showthread.php?18869-Miter-Saw-Brake > > I think after you remove power, if you short out the motor, , the motor > will come to a stop. You might want to short it out through a resistor > to avoid having the heat build up inside the motor windings. That heat pulse should be no worse than a fraction of a second at locked rotor amps, and it will only exist for a fraction of a second. The resistor I did use when I was building the interface for my mills spindle, because I read someplace that a dead short could result in field demagnetization under the right conditions. There I used a 20 ohm 20 watt resistor, which seems to be major overkill as I can just barely detect that heat after about 20 starts & stops in as many seconds. There, the stop down to about 30 rpm is maybe 1/2 second, and another half second has it stopped. Grabbing the spindle and turning it by hand is like stirring cold karo syrup. My dewalt chop saw has a brake on it that likely is what I am going to build, and it is quite brutally effective, so if trying to do a partial cut, its best to raise the chop 2 or 3 inches before releasing the trigger because the stop torque jacks it down about an inch. > I have a Delta Chop saw that has a button on the handle. After I am > done cutting I can just press the button and the saw comes to a complete > and sudden stop. My 12" Dewalt doesn't have a separate button, releasing the trigger does it. > Years ago I had a close encounter with a piece of wood that flew off a > table saw blade during a kickback. Nearly lost my left eye and I was > wearing goggles. Left eye is still intact though with one small scar. I had one come back & nearly break a rib 2 years ago. But that is fixable, google for "shark fin". Its a riving knife that is exactly the width of the blade with set, runs behind the blade within 1/8" of the teeth, covering the rear of the blade. Wood gets caught and thrown by the rising teeth on the back of the blade and if the teeth are shielded by the riving knife, no more kick back. If the knife is set exactly, even blade burns are much reduced. > My Dad ran his index finger across a table saw blade lengthwise when I > was a kid. He had a number of surgeries on it so he didn't lose it, > but it doesn't bend entirely. That was back in the 60's. > > I still have a table saw though, but not the one that kicked back on me. > That one had to go. Table saws are great machines, just have to be > careful with it. The riving knife, even if it is just a sliver of wood glued into the table insert behind the blade, helps a lot. But the shark fin actually mounts in place of the blade guard, rises and falls with the blade, covering it much better than just a fin glued into the zero clearance slot. It is, without a doubt, the single most safety improving table saw accessory ever. > Dave > > On 6/1/2011 11:13 AM, gene heskett wrote: > > Greetings all; > > > > Is anyone aware of a quick& dirty retrofit kit to brake an AC > > universal motor when the power is removed? > > > > I have a Ryobi BT-3000 table saw, which when kept properly adjusted, > > does a fine job. Its motor package is a universal motor that drives > > the blade with a gilmer belt. > > > > I nicked a finger on my table saw blade yesterday because it was still > > spinning 2 or 3 seconds after the kill switch was hit. Not seriously, > > just a slight nick that bled for 2 minutes, and is a red spot about > > 1/8" in diameter this morning. > > > > If practical, I would like to replace the existing power switch with > > one that is both handier because its not such a long reach under the > > table to hit it, and which shorts the motor in the off position, or > > at least applies a power resistor dummy load to it, commonly referred > > to as suicide braking. > > > > So, before I reinvent this wheel, is anyone aware of such an > > aftermarket device? > > ------------------------------------------------------------------------ > ------ Simplify data backup and recovery for your virtual environment > with vRanger. Installation's a snap, and flexible recovery options mean > your data is safe, secure and there when you need it. Data protection > magic? > Nope - It's vRanger. Get your free trial download today. > http://p.sf.net/sfu/quest-sfdev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) <http://tinyurl.com/ddg5bz> <http://www.cantrip.org/gatto.html> Avoid the Gates of Hell. Use Linux -- unknown source ------------------------------------------------------------------------------ Simplify data backup and recovery for your virtual environment with vRanger. Installation's a snap, and flexible recovery options mean your data is safe, secure and there when you need it. Data protection magic? Nope - It's vRanger. 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