"Steve Smith" wrote in message
...
I clearly need to replace some gears on my lathe, the question is how
many? There are four gears showing signs of wear, one of them really
bad. Replacing all four gets pretty expensive. The lathe is a 14 1/2"
Southbend.

First, naming the gears. Here's a picture of the group:
http://users.frii.com/sos/Steve/Overall.jpg

Parts Works names them as follows:
top gear in picture (this gear is on the spindle): "cone-pinion"
two gears just below cone-pinion: "twin gears"
gear which right twin gear drives (below R twin gear): "reverse gear"

Here is a top close up view of the cone-pinion:
http://users.frii.com/sos/Steve/Cone_Pinion.JPG

A close up view of the two twin gears:
http://users.frii.com/sos/Steve/Twin_Twin.jpg
The one on the right is clearly on its last legs.

A close up view of the right twin gear and the reverse gear beneath it:
http://users.frii.com/sos/Steve/Twin_Reverse.jpg
Again, the wear on the right twin gear is pretty serious.

I definitely need to replace the right twin gear. The cone-pinion
doesn't look so good, I don't know how to tell on the other two. I will
appreciate any recommendations and discussion .

Thanks,
Steve

Unless you're loading those gears heavily, I'd run them and not worry about
it. I would imagine it has taken years for them to wear to the point shown,
and were probably run far more then than you use them now. You could
conceivably have years of service left. If you feel driven to do any
replacing, I'd replace only the one(s) with the extreme wear, the ones with
marking on them in the pics. The others have countless years of service
life left in them, and there is no good reason to replace them, such as
matching teeth to teeth.

The nice thing about this situation is if the gears fail, they're likely to
do no harm aside from irritating you, unlike gears that run in an oil bath
transmission, where pieces ruin other pieces. I'd expect one tooth to
fail, and the gear assembly to come to a halt-----not much more. If the
failure were to occur in the middle of a threading cut, that would cost you
your project, but otherwise I can't think of anything bad that could occur.

Good luck

Harold