South Bend Manual Lathe

Link to: Machine Shop Main Page

		Eye protection required!

South Bend Lathe
The South Bend manual bench lathe
General Info
Make	South Bend
Model
Serial
Specs
Manual	Textbook
Asylum Info
Location	Machine Shop
Rubric	N/A
Training
Testing	Tool testing
Restrictions	red

See the Lathes category for notes on using all lathes

Safety

Link to: Safety notes on the Metal-cutting lathes category page

Changing the spindle speed

The South Bend lathe gear-box

This lathe features manual speed-changing where the user actually manipulates belts and gears inside the gearbox itself.

Do not attempt to adjust these items unless you have been properly trained and tool-tested.

Belts and Pulleys

The South Bend has two belts. The V-belt between the motor and the lathe drive shifts between high range and low range, and the flat belt between the lathe drive and the spindle allows adjustments within these ranges. To adjust the speed, loosen the belt tension lever on the left side of the machine, then move the belts to achieve the appropriate speed. Tighten the belt tension when you're ready to use the lathe

Motor, motor belt, and drive belt under the South Bend lathe. The motor belt (black, on the left) switches between the high speed range and the low speed range, and the orange leather belt (center) allows three different speeds within each range. Note that the loose belt tension here; adjusting either belt requires loosening the belt tension.

[picture of belt tension lever] [picture/chart of lathe speeds]

Back Gear

The back gear control on the lathe allows low speed, high torque rotation. To use the back gear, pull the back gear lever until the back gears engage with the spindle gear. If the gears are not meshing, manually spin the chuck while pulling the back gear lever to the rear.

Next, pull the coupling pin out of the largest drive gear. If you don't remove this pin, the chuck and gears will be locked. This will prevent the spindle from turning, and it's useful for loosening the chucks, but operating the lathe in this condition will cause the belts to rub.

The additional mechanical components in the back gear drivetrain creates more mechanical, gear-clanging noise. This noise is normal, but grinding or rubbing noises are not. Stop the lathe if you hear these kinds of noises.

To disable the back gear, move the back gear lever to the rear to disengage the back gear and re-insert the coupling pin. Ensure that the pin is fully seated in the cutout, which is in-line with the oil port on the middle spindle pulley.

Power Feed

Overview of the headstock spindle controls on the South Bend lathe. To engage back gear, pull the back gear lever (a) towards the front of the lathe and pull out the coupling pin (b). To disengage back gear, push the back gear lever towards the rear of the lathe and push in the coupling pin. Align the coupling pin with the oil port (c) before trying to push the coupling pin back into place.

The South Bend has both power carriage feed and power cross feed. The keyway in the leadscrew powers this power feeding, so the leadscrew must be enabled to use power feed. With the lathe powered off, enable the power feed by moving the power feed lever out of the neutral position and into the appropriate direction. Note that turning and facing operations typically require different power feed lever settings.

Overview of South Bend headstock power feed and thread pitch controls. To engage power feed, move the power feed lever (a) out of the center neutral position and into the position for the desired feed direction. Use the power feed/thread pitch adjustment levers (b) to adjust the feed rate (or thread pitch, if you're cutting threads)

With the lathe still powered off, move the power feed lever on the apron to the appropriate setting. Loosen the clutch knob to disengage the power feed before turning on the lathe. Tighten the clutch knob to engage the power feed, and confirm that the correct control knob is turning in the correct direction. Disengage the power feed by loosening the clutch.

Overview of South Bend apron controls. To enable power carriage feed, move the power feed selector (a) out of the central neutral position to the top position. Move it to the bottom position for power cross feed. To activate power feed, tighten the clutch knob (b). The half nut (c) and thread dial (d) are in this picture too, but they're for cutting single point threads, not power feed.

Two levers control the speed of the power feed. The leftmost position of these levers is the fastest feed speed, while the rightmost position is the slowest. Position E has a good range of feed rates, and this is typically the right setting for the first lever.