Does anyone know how to true a motor shaft shoulder?

[jteneyck]

The collar on my RAS fits against a shoulder on the motor arbor.  After lots of testing, I'm quite sure that shoulder is not exactly true.  I machined an aluminum collar to test runout, and remachined the inboard steel collar, as well.  Both measure about 0.002" of runout at their 4" OD.  At the OD of a 12" blade I typically measure around 0.005 - 0.006", which is exactly what would expect from the collar runout.  I've tried shifting the collars and blade in relationship to each other without significant improvement, meaning those are pretty true.  And that brings me back to the motor arbor shoulder.  

Is there a way to true that shoulder without having to take the motor apart and take it to a machine shop?  I would have to think there's some approach that's been developed for in the field fixes when people can't disassemble or move equipment.  I'm all ears if you know of a way.  Of course, I can take it apart, etc., but then I'll be faced with having to retune the saw.  

Or can a machine shop do it when the motor is still assembled?  Then I would only have to remove the motor and not take it completely apart.  

John

[Bob Vaughan]

Been there.
Its easier to take the motor apart while the motor is still mounted to the saw.
The rotor is easily chucked in a metal lathe and hopefully the little detent in the blade end is still good.  If not, a steady can hold the rotor by the bearing.  The actual cut takes off the thickness of a hair or less.  There's a whole lot more foolaround time than there is cutting time.
Usually there's enough of a little tail of the rotor sticking out of the inside bearing for the chuck to grab so that the bearing doesn't have to be removed.

I guess if you're steady enough and have a pointed live center, the job could be done on a wood lathe.

[jteneyck]

Been there.
Its easier to take the motor apart while the motor is still mounted to the saw.
The rotor is easily chucked in a metal lathe and hopefully the little detent in the blade end is still good.  If not, a steady can hold the rotor by the bearing.  The actual cut takes off the thickness of a hair or less.  There's a whole lot more foolaround time than there is cutting time.
Usually there's enough of a little tail of the rotor sticking out of the inside bearing for the chuck to grab so that the bearing doesn't have to be removed.

I guess if you're steady enough and have a pointed live center, the job could be done on a wood lathe.

Thanks Bob.  I took the motor apart when I got it to change the bearings, and did it on the saw.  You're right, very easy to do it that way, though I already had forgotten that's how I did it.  The threaded end has a recess for a hex key.  Hopefully, the detent outside of that is still good.  If it is, I might be able to do it on my little lathe; otherwise, it'll have to go to the machine shop.  

John

[Stwood_]

Build a wooden stand, with base, 6-8" tall, and attach a Dremel horizontally. Use a flat ended, round stone bit. Build it tall enough to reach the spindle. Remove guard and blade. Lock the switch on the saw on.
Turn dremel on and slide toward the flat face on the spindle and gently grind until you see it's made contact all the way around.

[jteneyck]

Build a wooden stand, with base, 6-8" tall, and attach a Dremel horizontally. Use a flat ended, round stone bit. Build  it tall  enough to reach the spindle. Remove guard and blade. Lock the switch on the saw on.
Turn dremel on and slide toward the flat face on the spindle and gently grind until you see it's made contact all the way around.

The problem with that approach is the shoulder is undercut, so you'd have to use a pointed cone type bit to reach into the shoulder, or at least past the larger diameter that the blade fits over.  Otherwise, you will have a little bump at the base of the shoulder that the blade will contact first.  

But I did buy some triangle shaped sharpening stones and dressed the shoulder with that.  No improvement in runout.  

For the time being I'm just living with it.  When it annoys me more, I'll take the motor apart and have a machine shop true the shoulder.  

Thanks. 

John

[Stwood_]

The problem with that approach is the shoulder is undercut, so you'd have to use a pointed cone type bit to reach into the shoulder, or at least past the larger diameter that the blade fits over.  Otherwise, you will have a little bump at the base of the shoulder that the blade will contact first.  

But I did buy some triangle shaped sharpening stones and dressed the shoulder with that.  No improvement in runout.  

For the time being I'm just living with it.  When it annoys me more, I'll take the motor apart and have a machine shop true the shoulder.  

Thanks. 

John

Yes, use the flat first then the pointed to clean out the shoulder.