Overview
The South Bend "Workshop" 9" (SB 9) horizontal lathe produced in the late 1940s through early 1950s was frequently delivered on optional cast iron legs rather than the more common bench-style or cabinet base. Field identification of these legs hinges on three independent physical signatures: the LA-320-1 casting number stamped inside the upper section of each leg, the 7 3/4" x 38" drilled chip-pan footprint, and the outboard drive-support geometry that mounts the motor pulley assembly behind the headstock. This reference documents the verification procedure, dimensional envelope, and known cross-manufacturer variants so a restorer can confirm originality before committing to installation.
Prerequisites for Field Identification
Before committing to an originality determination, gather the following data from the candidate lathe:
- Serial number of the headstock and of the bed (when stamped separately). The serial number of the SB 9 in the source example corresponds to April or May 1947 manufacture.
- Leg casting numbers. Inspect the inside surface of each leg near the top of the casting where ribs meet the upper flange. Legitimate LA-320 castings show
LA-320orLA-320-1in raised cast lettering. - Chip-pan mounting hole pattern. Measure center-to-center of the four corner bolt holes; original SB 9 / Logan configurations drill 7 3/4" x 38" on rectangular centers.
- Outboard drive bracket geometry. Photograph the angle-iron/pipe-leg assembly behind the headstock, including any shim tabs at the floor interface.
- Belt cover presence. Some legs integrate a height-adjusting knuckle at the top that is only visible when the belt cover is removed.
Technical Specifications
| Parameter | Value | Source / Notes |
|---|---|---|
| Lathes covered | South Bend SB 9" horizontal, 9" Workshop series | Source: 1947 unit, 10K companion unit cited |
| Manufacture window (sample) | April-May 1947 | Decoded from headstock serial number |
| Leg material | Cast iron | Painted to match SB 9 color in source example |
| Leg casting number | LA-320-1 (inside, upper section) | Same code on both legs in source |
| Manufacturer (by casting code) | Logan Actuator / Logan Lathe | "LA" prefix interpreted as Logan Actuator |
| Chip pan mounting footprint | 7 3/4" x 38" rectangular | Source measurement |
| Rear leg floor interface | Bolt-down tab with shim clearance | 2" pipe retrofit observed in source |
| Height adjustment | Knuckle near top of leg (inboard of belt cover) | Visible only with belt cover removed |
| SB workshop leg height vs Logan | Logan leg approximately 4" shorter | Source: dimension delta confirmed against SB worokshop lathe (sic) |
| Catalog reference | South Bend catalog W6312 (1952), p. 3 of 4 | Pictures similar outboard motor mount |
Casting Number Decoding
The LA-320-1 mark is a three-segment code. Each segment carries diagnostic value when verifying whether the legs were factory-supplied or sourced from a Logan lathe.
| Segment | Interpretation | Verification Step |
|---|---|---|
| LA | Logan Actuator / Logan Lathe foundry code | Cross-check against Logan serial lists; confirm cast pattern match on inside rib web |
| 320 | Pattern number for the leg family | Compare pattern profile with known Logan 9"/10" lathe legs |
| -1 | Pattern revision / dash variant | Verify dash number appears on both legs in matching orientation |
If the dash suffix differs between the two legs, the assembly was likely assembled from mixed sources and should not be marketed or documented as a matched original set.
Mounting Geometry and Chip Pan Footprint
The chip pan forms the load-distribution surface between the lathe bed ways and the leg castings. Original mounting relies on a rectangular bolt pattern; deviations are the first red flag for a retrofit or modified installation.
- Locate the four corner bolt holes on the chip pan flange.
- Measure longitudinal span (headstock-to-tailstock axis): 38".
- Measure transverse span (left-to-right across bed): 7 3/4".
- Verify hole diameter matches the supplied carriage bolts; Logan-supplied sets commonly use 3/8" or 7/16" fasteners depending on year.
- Confirm that the chip pan rests flat on the leg upper flanges with no rocking; an unflat pan indicates a non-original pan or warped castings.
Outboard Drive-Support Configuration
The early catalog illustration (South Bend W6312, 1952, p. 3/4) depicts an angle-iron bracket bolted to the rear leg, carrying a plate to which the motor pulley assembly mounts. In the field sample, the angle-and-plate subassembly had been replaced with a 2" pipe leg with a bottom tab for shimming and bolting to the floor. Document both states when classifying originality:
| Configuration | Components | Originality Status |
|---|---|---|
| Factory catalog depiction | Angle bracket + motor plate + cast iron rear leg | Matches catalog imagery |
| Field retrofit observed | 2" pipe leg + shim tab + cast iron front legs (LA-320-1) | Painted to match SB 9; non-catalog drive support |
| Hybrid (uncommon) | Cast iron legs with fabricated angle bracket | Requires individual evaluation |
Verification Procedure
- Photograph every casting face. Capture the inside rib where LA-320-1 is raised; photograph the floor tab interface.
- Measure chip-pan hole pattern. Use a tape or caliper; record both spans to 1/16" resolution. Compare against the 7 3/4" x 38" reference.
- Confirm dash-number parity. Both legs must carry an identical dash suffix (e.g., -1 / -1). Mixed dash numbers indicate a parts pair assembled from separate castings.
- Compare to Logan 9" lathe footprint. Place the leg casting alongside a known Logan 9" bed and verify bolt-hole alignment. Logan-to-Logan fit is the cleanest cross-check.
- Inspect for height-adjusting knuckle. A knuckle at the top of the leg (visible under the belt cover) is a Logan production feature and supports Logan origin.
- Check paint continuity. Original factory paint will extend under mounting flanges; field repaints often stop at visible edges and indicate rework.
- Document the drive-support bracket. Note whether the assembly is the catalog angle-and-plate or a later pipe-leg retrofit.
Troubleshooting Matrix
| Symptom | Likely Cause | Action |
|---|---|---|
| Casting number absent or ground off | Repaint or aggressive cleaning | Aspirin test / careful solvent wash; do not grind further |
| Dash number differs left vs right | Mixed-source pair | Source matched replacements from same pattern revision |
| Bolt holes do not align with SB bed | Cross-brand (Logan) legs fitted to SB bed | Verify with Logan bed; rework pattern if mixing is intentional |
| Height mismatch of 4" versus SB workshop | Logan legs shorter than SB equivalent | Build stiff sub-base with casters; account for 4" delta |
| Floor tab bent or shimmed | Settling or shimming prior to leveling | Re-shim, drill new floor anchors, torque to fastener spec |
| Knuckle missing at top of leg | Belt cover obscured feature; possibly removed | Remove belt cover; inspect for plugged threaded boss |
| Pipe-leg retrofit instead of angle bracket | Field repair / aftermarket drive support | Document as non-original; retain if structurally adequate |
Cross-Manufacturer Notes
The LA-320-1 casting is sourced from Logan (also referenced as Logan Actuator). Logan supplied a parallel 9" workshop lathe with a similar footprint, and the casting geometry is dimensionally compatible within a 4" height envelope relative to the SB workshop lathe leg. Operators who run both an SB 9 and an SB 10K can interchange LA-320 legs between the two units provided the chip-pan bolt pattern matches the bed in service. The source owner explicitly maintains a 10K setup and uses the SB 9 only when the 10K is occupied with a different job, so the 4" shorter leg height is acceptable when the SB 9 is mounted on a stiff castored sub-base.
Catalog and Documentation Cross-Reference
- South Bend Lathe Works catalog W6312 (1952), page 3 of 4: outboard motor mount illustration.
- Early South Bend catalogs: imagery matches, but no separate listing or part number for the cast iron leg option.
- Logan catalogs and parts lists: confirm LA-320 pattern reference and Logan 9" bed footprint.
FAQ
What does the LA-320-1 casting number on South Bend SB 9 legs indicate?
The LA-320-1 mark is a Logan (Logan Actuator / Logan Lathe) foundry code, not a South Bend production part. Both legs of an original Logan-sourced set will carry the same code on the inside of the upper casting; mixed dash numbers indicate a parts pair assembled from different sources.
What is the correct chip-pan mounting footprint for SB 9 cast iron legs?
The documented drilled footprint is 7 3/4" x 38" rectangular. Measure both spans to 1/16" resolution and verify hole alignment before bolting the pan to the legs.
How much shorter are Logan legs compared to the South Bend workshop legs?
Logan-supplied legs are approximately 4" shorter than the equivalent South Bend workshop legs. Compensate with a stiff castored sub-base or shim plinth to maintain ergonomic spindle centerline height.
How can I confirm whether the legs are original to a 1947 SB 9?
Check three independent signatures: the LA-320-1 casting mark, the 7 3/4" x 38" chip-pan bolt pattern, and the height-adjusting knuckle visible under the belt cover. South Bend catalogs never list the legs as a separately priced option, so LA-coded legs on an SB bed are most often a Logan retrofit.
Why does the rear leg sometimes show a pipe-leg replacement rather than an angle bracket?
Field retrofits commonly replace the catalog angle-and-plate motor support with a 2" pipe leg fitted with a floor shim tab. Document the configuration as non-original but verify structural adequacy before returning the lathe to service.
