Gear wear on my lathe
 

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

Hey Steve,
I only say this because it is what I am working on...have you
considered trying to make them...there is a lot of info out there on
cutting gears....just thought I would ask...might be a good learning
thing as well as saving you some bucks.

John

Good point. I'm keeping that as a backup plan. I really don't have
enough time for current projects....

Steve

CAMCOMPCO wrote:

Hey Steve,
I only say this because it is what I am working on...have you
considered trying to make them...there is a lot of info out there on
cutting gears....just thought I would ask...might be a good learning
thing as well as saving you some bucks.

John

"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

According to Harold and Susan Vordos :

"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.

[ ... ]

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.

I would in general agree, except that there is one simple (and
cost-free) step to postpone the day of needed replacement for quite a
while.

Note that of the twin gears, the one which is badly worn is the
one which is *always* in mesh with the "cone pinion", and transmitting
motion to the rest of the gear train, either directly, or (when in
reverse feed) through the second gear of the pair.

What I would consider doing is to interchange the two gears of
that pair, which would put the most subsequent wear on the relatively
un-worn one of the pair, and transmit power though the more worn one
only during reverse feeds or LH threading.

And -- make sure to keep them well lubed, of course.

Good Luck,
DoN.

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Email: | Voice (all times): (703) 938-4564
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"DoN. Nichols" wrote in message
...
According to Harold and Susan Vordos :

"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.

[ ... ]

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.

I would in general agree, except that there is one simple (and
cost-free) step to postpone the day of needed replacement for quite a
while.

Note that of the twin gears, the one which is badly worn is the
one which is *always* in mesh with the "cone pinion", and transmitting
motion to the rest of the gear train, either directly, or (when in
reverse feed) through the second gear of the pair.

What I would consider doing is to interchange the two gears of
that pair, which would put the most subsequent wear on the relatively
un-worn one of the pair, and transmit power though the more worn one
only during reverse feeds or LH threading.


Way to go, DoN! I didn't think of that, but it's sure to prolong the gear
life.

And -- make sure to keep them well lubed, of course.

Absolutely. I use Keystone 423, an open gear grease that comes in a spray
can. I think it's obsolete now (bought it back in '67!) but there's likely a
substitute on the market. Great stuff, doesn't run, and covers 100%
without dispersing to the sides. Goes on like water and ends up like *very*
sticky molasses.

Harold

..

On Thu, 06 Oct 2005 19:28:24 -0400, Steve Smith
wrote:

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"

Usually, I would not contradict Rose, but at least one of the names is
incorrect. According to the SB manual, the upper gear in your pic is
the Spindle Gear (PT30F2).

The Cone Pinion is a different part, located partially within the Cone
Pulley (hence the name).

The "Twin Gears" are called that in the manual, although we call those
the Reverse Idler Gears. For your lathe, they are PT27K32F2 and
PT27K28F2. 'Course, if they are "twins", why different numbers?

The Reverse Gear is PT28F2.

As mentioned elsewhere, these may last a long time yet, but might also
fail during a critical operation tomorrow.

I agree that the Twin Gear needs replacement at least. I don't know
if you can swap them as mentioned by DoN, since they have different
part numbers, but if so, that may prolong the life.

I respectfully disagree with Harold, that if they fail, they will not
do other damage. I've seen it happen in Logan Lathes, and the tooth
that gets kicked out CAN wedge into another gear damaging it and even
the shaft or stud upon which it is mounted.

Of course, if you leave the Reverse Bracket in neutral, there is no
load at all on any of these gears, and they SHOULD last forever. Kinda
tough to thread that way, though.

Good luck!

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In article , Scott S. Logan says...

Usually, I would not contradict Rose, but at least one of the names is
incorrect. According to the SB manual, the upper gear in your pic is
the Spindle Gear (PT30F2).

And most spindle gears on south bend lathes don't have any
Hardinge parts attached!!

:^)

Jim


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"Scott S. Logan" wrote in message
...
snip-----
I respectfully disagree with Harold, that if they fail, they will not
do other damage. I've seen it happen in Logan Lathes, and the tooth
that gets kicked out CAN wedge into another gear damaging it and even
the shaft or stud upon which it is mounted.

No problem with the disagreement, for I, too, have reservations about my
comment, and I bow to your expertise as a manufacturer of lathes. My
experience comes from running them, and I've never experienced such a
failure.

My reservations come not only for the circumstance you described, but one
whereby the gear is not made of cast iron, but steel, and the tooth folds
over under load and wedges, much the same as you described. I shudder to
think of the consequences. I was thinking optimistically, if not
rationally.

My logic in this matter, based on many unknowns, is that the OP uses the
machine for pleasure, likely well under capacity, so it's not stressed much,
so it's unlikely to fail, and, given a little luck, should the cast iron (?)
gear fail, it would toss the tooth, not wedge it. That would be a decision
based on economics, and, with luck, would be a good one.

Yeah, I have heard of Murphy! I know him (or his law) quite well. g

Had I been armed with more information, such as the machine is used for
gain, and must be up and running, I'd have likely suggested the replacement
of the two gears, without giving any thought to anything less. It's really
hard to know the circumstances of some folks. Could be the kids need
shoes, the doctor bill remains unpaid for the last delivery, and the
cupboards are bare. In that case, the gamble may be a rational option.

Harold