Start with the problem. Find the right checks, repair guidance and parts for your TOS lathe.
Select a symptom below. Check the full model and machine version before using a procedure or ordering parts. SN, Classic and SV machines must not be treated as identical.
Clutch slipping · Gearbox running hot · Cross-slide play · Feed problems · Parts & repair sets
Before opening covers or inspecting mechanisms, stop and isolate the machine and prevent accidental starting. Adjustment and repairs should be carried out by competent personnel using the manual for the actual machine.
Common lathe problems
The clutch slips under load
Check: confirm the machine version and which clutch is affected. Do not assume that both clutches need tightening or that the discs must immediately be replaced.
Next step: for the documented SN 55–63–71 arrangement, the manual permits adjustment of a slipping clutch after the machine has cooled. The result must provide engagement without slipping and disengagement without driving the spindle or causing excessive heating.
Read the SN 55–63–71 clutch adjustment guide →
Parts: internal and external clutch discs only after identification and inspection. Send your machine plate and clutch photos.
The spindle keeps turning with the clutch disengaged
Check: record the exact model, lever position and whether the fault appeared after an adjustment. Do not reach into or work on the mechanism while it is running.
Next step: stop operation and arrange a clutch/control inspection. The SN 55–63–71 manual requires the disengaged clutch not to drive the spindle. Further tightening is not the default remedy. Procedures for this SN arrangement must not be applied to SV 18 machines.
The spindle speed gearbox is running unusually hot
Check: note the model, operating conditions and oil and ambient temperatures if these can be measured safely. Consult the lubrication instructions for your version before adding or changing oil; do not guess the oil grade.
Next step: the SN 55–63–71 manual calls for checking the gearbox, including clutch and brake clearances, when oil reaches 40°C or more above ambient. Excessive heating, abnormal noise or a dragging spindle requires investigation, not a larger motor or tighter clutch setting.
Parts: identify the cause first. Arrange a lubrication, clutch and brake inspection.
The cross-slide handwheel turns before the slide moves
Check: distinguish lost motion when reversing the handwheel from movement of the slide in its guideway. Record the symptom with the machine isolated and provide the model, screw and nut identification and photographs.
Next step: the SN 32/50/71 manual, section 4.11, describes guideway clearance adjustment by a gib. It does not establish that tightening the gib will remove screw-and-nut backlash. Have the source of lost motion identified before choosing a repair.
Parts: if screw/nut wear is confirmed, match the screw and nut to the model and metric/inch version. Bearings, bushes and fasteners belong in the repair only where the actual assembly requires them. Browse SN 40-50 parts or request a matched set.
The top slide has play or is difficult to move
Check: distinguish guideway play from lost motion in the screw drive. Identify the top-slide arrangement and metric/inch version.
Next step: section 4.10 of the SN 32/50/71 manual identifies a gib for guideway clearance adjustment. A screw replacement procedure and final setting must be matched to the specific slide; do not use the cross-slide procedure for the top slide.
Parts: top-slide screw and nut, or guideway components, depending on the identified fault. Identify top-slide parts →
The power feed drops out or will not engage
Check: note whether the problem affects longitudinal feed, cross feed, one direction or all feeds. Record the control positions with the machine stopped.
Next step: use the operating and protection-system instructions for the exact model. Section 4.9 of the SN 32/50/71 manual describes an apron disengagement system with factory-set forces. Do not defeat this protection or increase its setting simply to keep the feed engaged. Repeated disengagement needs diagnosis of the load and mechanism.
Parts: apron control and feed parts after inspection. Send the model and affected feed direction or request service.
The lead screw no longer drives during threading
Check: confirm the control settings against your manual and distinguish the lead-screw drive from the feed-rod drive.
Next step: section 4.8 of the SN 32/50/71 manual describes a shear pin that interrupts the lead-screw drive under excessive load. On that arrangement, replacement access is obtained by releasing the spring retainer and moving the ring shown in figure 4.8-1. Identify and correct the overload cause before replacing the specified pin. This is not a universal diagnosis for every loss of drive.
Parts: use the specified shear pin for the exact assembly; do not substitute an arbitrary stronger pin or bolt. Identify the correct shear pin →
The spindle takes too long to stop
Check: identify the model and whether it has a multi-plate brake, an additional band brake or another arrangement.
Next step: section 4.7 of the SN 32/50/71 manual has different brake instructions for different models. A stopping-time figure or adjustment from another version is not interchangeable. Stop using a machine with unreliable braking and arrange adjustment or repair to its own instructions.
Parts: brake discs or a brake band only after the brake type and condition are confirmed. Clutch discs and brake discs must not be selected by appearance alone. Request brake service →
A tool-post stud or component will not come out
Check: identify the exact component on the assembly drawing. A tool-post stud, pivot and feed screw are different parts.
Next step: stop before applying a press, impact or heat when the retention and removal direction are unknown. Send the drawing position and photographs so the assembly can be identified. A model-specific dismantling procedure is needed before using force.
Parts and repair sets
Know the part already? Browse your machine series. Need several parts for one repair? Request a matched set with your model, serial number, drawing and metric/inch version.
- SN 40 / SN 50 spare parts
- SN 55 / SN 63 / SN 71 spare parts
- 803 218 internal clutch disc set, 16 pcs — listed for SN 32 / SN 40 / SN 50. Internal discs only; this is not a complete clutch kit and is not identified here for SN 55-63-71.
For a complete repair set: we first confirm the parts and quantities for your actual assembly. A cross-slide set may require a matched screw and nut plus the applicable bearings and fixing parts. Nothing is assumed to fit solely because it is labelled “SN 50”.
Request a complete repair set →
Prefer us to repair the machine?
STAP handles diagnosis, repairs and overhauls. Service and repairs · Lathe overhauls · Lathes for sale
Technical basis
Technical references: TOS SN 55–63–71, section 4.6; TOS SN 32/50/71, sections 4.8–4.11 and the model-specific brake instructions in section 4.7. These references apply only to the arrangements described in those manuals. Initial symptom checks are guidance for identifying a fault, not confirmation that a particular part has failed.
Owner questions used to choose these topics
Owners have reported SN 50 gearbox heating, SV 18 RA clutch/control problems and SN 50 tool-post dismantling questions. Forum posts help identify useful topics; they do not establish the correct repair settings, compatibility or diagnosis for your machine.