Re: SB 9 A Leadscrew Drawing wanted

Steve Wells

There’s an error in size on the keyway shaft, where it says 0.645, that should be 0.6245…sorry




From: <> On Behalf Of Steve Wells
Sent: Monday, September 20, 2021 2:26 PM
Subject: Re: [SouthBendLathe] SB 9 A Leadscrew Drawing wanted


Sam, If I understand correctly, you want to convert your Model B Leadscrew to a Model A.


A gear box thrust collar is required on the Model A screw.


1.125 OD x 0.750 ID x  0.750 length.


first check you screw lengths to make sure this modification will work with your gearbox, and rear mount.


Before you position the thrust collar, mark from the left edge of the relief cut for the lead screw acme threads, towards the threaded end of the shaft (left) 4.9375 inches.


Cut off the B screw at that measurement.

Now working left to right, mark 0.7031, cut a 0.125 width thread relief on the left side of this mark to .0375 OD. Now you have the new Model A lead screw retaining thread area, turn this area to 0.495.

Thread to 1/2 -13.


From the right side of the above thread relief, mark 0.4688, cut a turning relief on the left side of this mark, 0.0625 width, to 0.6094 OD. Turn the marked shaft area between the thread relief and the turning relief area to 0.645 OD.


From the right side of the turning relief, mark 1.501, this is the left side front of the thrust collar position. Position and fixture your thrust collar to the left of this mark to allow for the collar to be faced square to the leadscrew (0.010-0.015) or so. Face the collar after fixturing, back to 1.501 again.


Set up and mill the keyway for the 3/16 x 3/16 x 7/16 drive key from the turning relief, left to end of the threads, chase the threads and chamfer the end 1/32.


Drill and pin the Thrust collar.


Photo attached,


Hope that helps,





From: <> On Behalf Of Sam
Sent: Sunday, September 19, 2021 10:40 PM
Subject: [SouthBendLathe] SB 9 A Leadscrew Drawing wanted


SB 9 A  Lead-screw Drawing wanted

Does anyone have a drawing for a 9A leadscrew ?

The end that mates with the gearbox is the problem.

I'm looking at  B to A conversion and have no idea how it's supposed to be

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