S/G communtator question
 

I have a S/G apart from my Original, and have a brush set and bearings (boy did it ever need those!) My question is, how much below the surface of the copper commutator does the slot need to be undercut between the two?

Thanks
John

Maybe it'll help if I ask it another way... if you've taken yours apart and it still worked, does anyone remember how deep the slots are between the copper commutator pieces? I'll put mine back together as as, but I'm curious to know how they looked new and how much life is left.

I've heard of "undercutting" to increase this, and I could probably fixture my small lathe to do this, but I won't bother if it's not needed.

Thanks! Will try to get some pictures tonight
John

The members that do this type of work are probably very limited on here. I have done what you are talking about and I just simply made sure there was a groove, about 1/16" deep. I don't know if that is correct, but in my case, it worked.

If I had to open up a S/G again, I think I would take it to a professional shop and have them go through the unit.

The last time I did it (MANY moons ago!!) I simply took a hack saw blade and pulled it between the sections.

I never measured the depth, 1/16" is probably a good number.

The function of the groove is to eliminate the conductive path from one section to the next, so not much depth is needed.

I think most of what I was doing with the hacksaw blade was cleaning the existing groove, rather than actual cutting.

Dirt and carbon from the brushes seems to pack into the grooves.

If you are going to turn the commutator, look at it at each end where it was not worn by the brushes.

That "virgin" area will show how deep the undercut was previously.

good info
 

Thanks for the good info..as with most things there's a lot of science and experience in this craft. I found some good info here too:

"http://martindaleco.com/HTML/MetalWorkingMicaSaws/Helpful_Hints_MicaSaws.htm"

Looks like the important factors are leaving a pocket so that the brushes ride smoothly over the commutator , the pockets are clean and that the commutator is as smooth as practical. Looks like 1/32- 1/16th is right on as you say.

Now to get it cleaned up... and ready to reassemble (and take some pix)

John