Definition
Work standards (作業標準, sagyo hyojun) are the broad category of documents that define how work is performed. They exist in every department of a Toyota factory — maintenance, engineering, quality, production engineering, material handling, and on the shop floor. Any document that specifies the correct way to perform a job or maintain a condition is a work standard.
This is not the same thing as standardized work (標準作業, hyojun sagyo). The word order in Japanese matters. Standardized work is one very specific type of document used in repetitive production operations, built around takt time, work sequence, and standard in-process stock. Work standards are everything else — and they vastly outnumber standardized work documents in any factory.
Japanese Origin
Sagyo hyojun (作業標準) combines 作業 (sagyo, “work” or “operations”) with 標準 (hyojun, “standard” or “criterion”). The word order is reversed from standardized work (標準作業, hyojun sagyo). In Japanese this is not a trivial distinction — sagyo hyojun means “standards for work” (the documents that govern how jobs are done), while hyojun sagyo means “standardized operations” (the specific three-element production standard tied to takt time).
Most English-language lean literature collapses this distinction, treating “standard work” and “work standards” as interchangeable. At Toyota they are not.
The Distinction That Matters
Standardized work (hyojun sagyo) is highly specialized:
- Requires takt time as a defining element
- Built up from three specific documents: Process Capacity Sheet, Standardized Work Combination Table, and Standardized Work Chart
- Applies only to repetitive production operations where cycle time can be measured against takt
- Used by production operators on the shop floor
Work standards (sagyo hyojun) are universal:
- Do not require takt time
- Do not use the three standardized work documents
- Apply to every department — maintenance, engineering, quality, production preparation, logistics, and more
- Created mainly before production begins, during equipment installation, run-off, and launch preparation
- Updated throughout the life of the equipment and process
The practical consequence: the overwhelming majority of documented standards in a Toyota factory are work standards, not standardized work. A single machining line may have only a handful of standardized work charts for operators, but dozens or hundreds of work standards covering equipment, tooling, quality criteria, maintenance procedures, and technical specifications.
Types of Work Standards
Work standards span a wide range of documents. The following categories illustrate the breadth — this is not exhaustive, but it shows how much territory work standards cover compared to the narrow scope of standardized work.
Production Engineering and Quality
- Operation Drawing (工作図, kosakuzu) — intermediate machining drawing for each process step, showing stock removal, dimensions, tolerances, and datum locations
- Quality Check Sheet (品質標準書, hinshitsu hyojun-sho) — precision measurements, tolerances, instruments, sampling methods, and judging criteria for each operation
- Tooling Layout Drawing (刃具配置図, haguhaichi zu) — tooling manufacturer, tool number, dimensions, and placement for each position on a machine
- Static Accuracy Sheet (静的精度表, seiteki seido-hyo) — machine precision record from run-off documenting spindle run-out, axis accuracy, and baseline machine condition
- Gage Instruction Sheet — specifies which measuring instruments to use, how to use them, calibration requirements, and measurement technique for each quality characteristic
Maintenance and Equipment
- Operating Instructions (取扱い説明書, toriatsukai setsumeisho) — procedures for operating the equipment
- Maintenance Instructions (保守説明書, hozen setsumeisho) — scheduled and corrective maintenance procedures
- Lubrication Standards (給油基準書, kyuyu kijunsho) — lubrication points, oil types, quantities, and intervals for each machine
- Machine Assembly Drawings (機械組付図, kikai kumitsuke zu) — detailed assembly and component layout
- Consumable Parts Diagrams and Parts Lists (消耗性部品図, 使用部品一覧表) — wear items identification and replacement specifications
- Electrical Circuit Diagrams (電気回路図, denki kairo zu) — wiring and electrical system documentation
- Hydraulic Circuit Diagrams (油圧回路図, yuatsu kairo zu) — hydraulic system layout and specifications
- Pneumatic Circuit Diagrams (空圧回路図, kuatsu kairo zu) — pneumatic system layout
- Lubrication Circuit Diagrams (潤滑回路図, junkatsu kairo zu) — lubrication delivery system layout
- Coolant Circuit Diagrams (クーラント回路図, kurant kairo zu) — coolant system layout and flow paths
- Control Circuit Diagrams (制御関係図, seigyo kankei zu) — control system documentation
- Cycle Diagrams (サイクル線図, saikuru senzu) — machine cycle timing and sequence
- I/O Address Lists (I/Oアドレスリスト) — input/output mapping for programmable controllers
- Equipment Layout Diagrams (機器配置図, kiki haichi zu) — physical arrangement of equipment and components
General
- One-Point Lessons — focused single-topic instruction sheets for specific skills or knowledge
- Skills Training Standards — step-by-step instruction for training operators on specific tasks
- Safety Standards — required safety procedures, PPE, lockout/tagout sequences
- Material Handling Standards — how to transport, store, and present materials to the line
When Work Standards Are Created
Work standards are primarily created before production — during equipment design, procurement, installation, run-off, and launch preparation. When Toyota buys a new machine, the equipment manufacturer submits documentation covering the machine’s design, circuits, accuracy, and maintenance requirements. Production engineering creates operation drawings, tooling layouts, and quality check sheets during process planning. All of this happens before a single production part is made.
Work standards are also created and updated after production begins — as maintenance discovers new failure modes, as engineering improves processes, and as quality requirements change. But the bulk of work standards are established pre-production as the technical foundation for running the process correctly.
This contrasts sharply with standardized work, which can only be created during production — because it requires observing actual cycle times against actual takt time with actual operators performing the work.
Common Misunderstandings
Calling everything “standardized work.” In most lean implementations outside Toyota, any document that describes how to do a job gets called “standardized work.” This obscures the critical distinction. If there is no takt time, no process capacity sheet, no standardized work combination table, and no standardized work chart — it is a work standard, not standardized work. This is not a minor semantic point. The methods for creating, maintaining, and improving work standards are different from those for standardized work.
Underestimating the volume. Because lean literature focuses almost exclusively on standardized work, many practitioners assume that the three standardized work documents are the main documentation system in a Toyota factory. In reality, a single machining line may have hundreds of work standards — circuit diagrams, lubrication charts, accuracy records, tooling specifications, quality criteria — compared to perhaps a dozen standardized work charts for operators. The work standards are the technical infrastructure that makes production possible.
Neglecting maintenance documentation. A large proportion of work standards are maintenance-related: lubrication standards, circuit diagrams, assembly drawings, accuracy tables, parts lists. These documents are essential for equipment reliability and form the foundation of TPM and autonomous maintenance. Organizations that focus only on operator-facing standardized work miss this entire category.
Creating work standards after problems occur. At Toyota, work standards are created proactively during pre-production. The purpose is to document the known-good condition so that any deviation can be detected and corrected. Creating standards only after problems emerge — as a reaction rather than prevention — defeats the purpose of having standards in the first place.