I'm no expert but I think I would tackle it like this. Remove the lathe head. It is held on by two bolts underneath. This will provide access to the top screws holding the gear box on. Remove the screws holding the lead screw support near the tail stock. Remove the gearbox screws. The whole thing should come off assuming you already disconnected the apron.
Before doing the above., remove the carriage top from the apron. It is held on buy the two slotted screws in the top and a flat piece of steel at the back of the bed. With the top removed, you can look into the top of the apron. There are some YouTube videos on this.
Al

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of mike allen
Sent: Friday, July 15, 2022 10:24 PM
To: SouthBendLathe@groups.io
Subject: [SouthBendLathe] 9" Toolroom lathe carriage won't move



A bud asked me to come over & look at his lathe a South Bend 9A .
It's one of the fancy
ones large dials spindle cover on the headstock & came with a taper attachment . The
Numbers on the change gear plate xx8344ZD . Ok so now the the problem , the carriage
will only move @ 3/4"- 1" . The hand wheel for moving the apron will turn from @
one-o clock to 12 o clock on , so not even a full revolution .We removed the saddle & the
lead screw support thinking we would be able to slide the apron off the lead screw but
no go . it will still only move the same 3/4-1" & stop & its a hard stop . So next we removed the taper pin holding the hand wheel on & pushed the pinion shaft into the apron so
the pinion gear had no contact with the gear that contacts the rack & still no
movement only the 3/4" - 1" . We tried spinning the input gear for the gearbox to try
to drive the apron off the leadscrew but the bolt the holds the gears on loosened so
that was a dead end . I marked the gear that runs in the rack & in the almost full
revolution the handwheel makes the rack gear only moves @ 1/3 of a revolution .
Unfortunately the unit is stuck maybe a quarter down the leadscrew from the gearbox. When it stops it's like it's hitting a brick wall , it's a hard stop
We were hoping we might be able gently push the right side of the leadscrew down
enough to disengage the rack gear from the rack to slide the assembly off , but it's just to close to the gear box & don't want to bend the leadscrew . I've had one of these lathes into
as many pieces you can get with out removing the feet & I'm at a loss as to what the problem just might be . We left the required parts reinstalled for the weekend so we could think
about this some more . I'm going to borrow a bore scope & see if I can see any more but
I'm at a loss on this .
Any of you folks have any ideas ?
thanks
animal

So next we removed     the taper pin holding the hand wheel on &
pushed the pinion shaft into the apron so
    the pinion gear had no contact with the gear that contacts the rack
& still no
     movement only the 3/4" - 1" .

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

        Yeppers it is a head-scratcher & my hair is gettin too thin for much head-scratchin

        He uses this lathe mostly for brass , but on occasion it has seen some steel . I'm not sure what he was workin on when the problem popped up . Half-nuts are fine . In my head it either

        is something caught in the worm somewhere , or the rack gear . I'm leaning more towards something caught in the rack gear just cause of the way it stops . The biggest stick in our

        spokes is that we're were trying not to remove the head-stock , & the only way we can get to the gear-box screws or the rack screws is removing the head-stock . Once we swallow

        the fact that we have to pop the head-stock off we'll be doing a autopsy once we have the apron/leadscrew on the bench .

        thanks

        animal

On 7/16/2022 7:40 AM, wlw19958 wrote:

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

--
-George M.

Mike,
How about engaging the gear train and spinning the chuck by hand to rotate the lead screw? Compressed air, a blow gun, and eye protection? I'm thinking a chip got stuck in the lead screw keyway.


Thanks, George Meinschein 150 Brittany Drive Freehold, NJ 07728 gmeinschein@... Cell#: 732-580-1736

Sent from Proton Mail mobile



-------- Original Message --------
On Jul 16, 2022, 4:54 PM, mike allen < animal@...> wrote:

        Yeppers it is a head-scratcher & my hair is gettin too thin for much head-scratchin

        He uses this lathe mostly for brass , but on occasion it has seen some steel . I'm not sure what he was workin on when the problem popped up . Half-nuts are fine . In my head it either

        is something caught in the worm somewhere , or the rack gear . I'm leaning more towards something caught in the rack gear just cause of the way it stops . The biggest stick in our

        spokes is that we're were trying not to remove the head-stock , & the only way we can get to the gear-box screws or the rack screws is removing the head-stock . Once we swallow

        the fact that we have to pop the head-stock off we'll be doing a autopsy once we have the apron/leadscrew on the bench .

        thanks

        animal

On 7/16/2022 7:40 AM, wlw19958 wrote:

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

--
-George M.

On Jul 16, 2022, at 6:37 PM, mike allen <animal@...> wrote:



        I have a crank I made for my 9A for turning the spindle & will have that in my kit bag when i go back over on monday . Though I hate using compressed air I did blow it out on friday

        but to no avail . I have a can of carb cleaner with the lil straw & some small fuel line that fits over the straw so I can aim where I want it to go . I just don't want to get any chemicals

        in the clutch as I don't remember just what the clutch material is . I do have the gearbox set up for the fastest feed so if we do get some movement we get the most bang for our buck

        if we get any motion .

        thanks

        animal

On 7/16/2022 3:09 PM, George Meinschein via groups.io wrote:

Mike,
How about engaging the gear train and spinning the chuck by hand to rotate the lead screw? Compressed air, a blow gun, and eye protection? I'm thinking a chip got stuck in the lead screw keyway.


Thanks, George Meinschein 150 Brittany Drive Freehold, NJ 07728 gmeinschein@... Cell#: 732-580-1736

Sent from Proton Mail mobile



-------- Original Message --------
On Jul 16, 2022, 4:54 PM, mike allen < animal@...> wrote:

        Yeppers it is a head-scratcher & my hair is gettin too thin for much head-scratchin

        He uses this lathe mostly for brass , but on occasion it has seen some steel . I'm not sure what he was workin on when the problem popped up . Half-nuts are fine . In my head it either

        is something caught in the worm somewhere , or the rack gear . I'm leaning more towards something caught in the rack gear just cause of the way it stops . The biggest stick in our

        spokes is that we're were trying not to remove the head-stock , & the only way we can get to the gear-box screws or the rack screws is removing the head-stock . Once we swallow

        the fact that we have to pop the head-stock off we'll be doing a autopsy once we have the apron/leadscrew on the bench .

        thanks

        animal

On 7/16/2022 7:40 AM, wlw19958 wrote:

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

--
-George M.

On Jul 16, 2022, at 9:51 PM, ROBERT T KELLERMANN <rtjkeller@...> wrote:



Put the right side handle of the qcgearbox down so it disengages the gearbox from the lead screw 

Turn the lead screw by hand it should turn free. If not it could be in drive train/clutch for the apron

Bob

On Jul 16, 2022, at 6:37 PM, mike allen <animal@...> wrote:



        I have a crank I made for my 9A for turning the spindle & will have that in my kit bag when i go back over on monday . Though I hate using compressed air I did blow it out on friday

        but to no avail . I have a can of carb cleaner with the lil straw & some small fuel line that fits over the straw so I can aim where I want it to go . I just don't want to get any chemicals

        in the clutch as I don't remember just what the clutch material is . I do have the gearbox set up for the fastest feed so if we do get some movement we get the most bang for our buck

        if we get any motion .

        thanks

        animal

On 7/16/2022 3:09 PM, George Meinschein via groups.io wrote:

Mike,
How about engaging the gear train and spinning the chuck by hand to rotate the lead screw? Compressed air, a blow gun, and eye protection? I'm thinking a chip got stuck in the lead screw keyway.


Thanks, George Meinschein 150 Brittany Drive Freehold, NJ 07728 gmeinschein@... Cell#: 732-580-1736

Sent from Proton Mail mobile



-------- Original Message --------
On Jul 16, 2022, 4:54 PM, mike allen < animal@...> wrote:

        Yeppers it is a head-scratcher & my hair is gettin too thin for much head-scratchin

        He uses this lathe mostly for brass , but on occasion it has seen some steel . I'm not sure what he was workin on when the problem popped up . Half-nuts are fine . In my head it either

        is something caught in the worm somewhere , or the rack gear . I'm leaning more towards something caught in the rack gear just cause of the way it stops . The biggest stick in our

        spokes is that we're were trying not to remove the head-stock , & the only way we can get to the gear-box screws or the rack screws is removing the head-stock . Once we swallow

        the fact that we have to pop the head-stock off we'll be doing a autopsy once we have the apron/leadscrew on the bench .

        thanks

        animal

On 7/16/2022 7:40 AM, wlw19958 wrote:

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

--
-George M.

Or the 1/2 nuts

On Jul 16, 2022, at 9:51 PM, ROBERT T KELLERMANN <rtjkeller@...> wrote:



Put the right side handle of the qcgearbox down so it disengages the gearbox from the lead screw 

Turn the lead screw by hand it should turn free. If not it could be in drive train/clutch for the apron

Bob

On Jul 16, 2022, at 6:37 PM, mike allen <animal@...> wrote:



        I have a crank I made for my 9A for turning the spindle & will have that in my kit bag when i go back over on monday . Though I hate using compressed air I did blow it out on friday

        but to no avail . I have a can of carb cleaner with the lil straw & some small fuel line that fits over the straw so I can aim where I want it to go . I just don't want to get any chemicals

        in the clutch as I don't remember just what the clutch material is . I do have the gearbox set up for the fastest feed so if we do get some movement we get the most bang for our buck

        if we get any motion .

        thanks

        animal

On 7/16/2022 3:09 PM, George Meinschein via groups.io wrote:

Mike,
How about engaging the gear train and spinning the chuck by hand to rotate the lead screw? Compressed air, a blow gun, and eye protection? I'm thinking a chip got stuck in the lead screw keyway.


Thanks, George Meinschein 150 Brittany Drive Freehold, NJ 07728 gmeinschein@... Cell#: 732-580-1736

Sent from Proton Mail mobile



-------- Original Message --------
On Jul 16, 2022, 4:54 PM, mike allen < animal@...> wrote:

        Yeppers it is a head-scratcher & my hair is gettin too thin for much head-scratchin

        He uses this lathe mostly for brass , but on occasion it has seen some steel . I'm not sure what he was workin on when the problem popped up . Half-nuts are fine . In my head it either

        is something caught in the worm somewhere , or the rack gear . I'm leaning more towards something caught in the rack gear just cause of the way it stops . The biggest stick in our

        spokes is that we're were trying not to remove the head-stock , & the only way we can get to the gear-box screws or the rack screws is removing the head-stock . Once we swallow

        the fact that we have to pop the head-stock off we'll be doing a autopsy once we have the apron/leadscrew on the bench .

        thanks

        animal

On 7/16/2022 7:40 AM, wlw19958 wrote:

Hi There,

Boy, that is a head-scratcher. 

First off, you say this lathe is the one your friend uses most.  I take it
this problem came up fairly recently?  What was he doing last time
he was using this lathe (just prior to the advent of its current problem)?

I know this is probably NOT the problem but have you check the half-nuts
to make sure they aren't somehow causing the problem? 

If you have removed the saddle and disengaged the pinion gear from the
rack, Then the only thing I can think of is the worm gear that slides along
the lead screw.  Either something has gotten in there or the pin and/or the
key is binding on the lead screw. 

As others have suggested, You next step is to unbolt the QC gearbox and
remove the QC gearbox, lead screw and apron as a unit.  Once the assembly
is out and lying so the back of the apron is exposed, the problem may present
itself.

As a pure guess, I think it is possible the worm gear has jammed onto the
lead screw and the threaded collar that holds the worm gear in the apron
casting is loose allowing the apron to have the limited travel thus displayed. 
Removing he QC gearbox, lead screw and apron will show for sure.

Good Luck!
-Blue Chips-
Webb

--
-George M.

Make sure that the taper attachment locking nut isn’t engaged. On my SB 9” lathe, the taper attachment has a locking nut that engages it and also another screw which much be removed whenever I use it. I remember that I once had both the taper engaged and the other screw in also. It locked the carriage up in a similar way you describe.

Sounds like the worm drive key is riding out of position when the saddle is moved, I had a similar issue with mine after stripping it to install new felts, you can check this with a torchlight and see if it jumps out after moving it, if it jumps out it will allow about an inch of movement until it jams up. 

OK, waiting for the outcome...

Payson.