Extend Engineer MCP

.github/workflows/ci.yml

@@ -39,5 +39,11 @@ jobs:
       - name: Verify the demo runs
         run: npm run demo
 
+      - name: Verify the CLI list pipes to standard output
+        run: |
+          node dist/index.js --version
+          node dist/index.js --list | grep -q "beam_bending"
+          node dist/index.js --list | grep -q "interference_fit"
+
       - name: Verify the package contents
         run: npm pack --dry-run

README.md

@@ -6,7 +6,7 @@
 [![Node](https://img.shields.io/badge/Node-%3E%3D22.13-brightgreen.svg)](package.json)
 
 Engineer MCP is a Model Context Protocol server for mechanical-engineering calculations.
-It gives coding agents verified answers for beams, bolts, springs, shafts, bearings, stress, sections, and units.
+It gives coding agents verified answers for beams, bolts, springs, shafts, bearings, stress, sections, fits, and units.
 Every result shows the formula, the method, and the source.
 
 ## What it provides
@@ -24,6 +24,7 @@ The release covers these domains:
 - Bearing rating life to ISO 281.
 - von Mises equivalent stress.
 - Cross-section properties.
+- Press and shrink fit analysis by Lamé theory.
 - Dimension-safe unit conversion.
 - Material property lookup.
 
@@ -38,7 +39,7 @@ The unit layer knows the dimension of every unit.
 It rejects a conversion between incompatible quantities.
 For example, it rejects a torque-to-energy conversion.
 
-Safety factors appear only when you provide a yield strength.
+Safety factors appear only when you provide the data they need.
 The tool never hides an assumption.
 Warnings surface when a method uses an approximation.
 
@@ -49,6 +50,7 @@ Warnings surface when a method uses an approximation.
 | `beam_bending` | Bending stress, deflection, and safety factor. |
 | `section_properties` | Area, inertia, and section modulus of a shape. |
 | `bolt_strength` | Stress area, preload, and capacity of a bolt. |
+| `interference_fit` | Interface pressure, hoop stresses, and friction capacity of a press or shrink fit. |
 | `spring_design` | Spring rate, shear stress, and safety factor of a compression spring. |
 | `shaft_analysis` | Torsion stress, twist, and critical speed. |
 | `bearing_life` | ISO 281 rating life in revolutions and hours. |
@@ -147,6 +149,26 @@ References:
   - Machinery's Handbook (Thirty-first edition)
 ```
 
+A call to `interference_fit` for a steel hub on a solid steel shaft with 50 µm of diametral interference:
+
+```text
+Interface pressure                    77.62 MPa
+Hub tangential stress                 129.4 MPa
+Shaft tangential stress               77.62 MPa
+Axial force capacity                  73.16 kN
+Torque capacity                       1.829 kN·m
+Shaft safety factor                   3.865
+Hub safety factor                     1.656
+Torque safety factor                  1.829
+
+Method: Interference fit by Lamé thick-cylinder theory
+Formula: p = delta / (d K); K = (1/Eh)((Ro^2+r^2)/(Ro^2-r^2)+nu_h) + (1/Ei)((r^2+ri^2)/(r^2-ri^2)-nu_i); F = 2 pi r L p mu; T = F r
+References:
+  - Shigley's Mechanical Engineering Design (Tenth edition, 2015)
+  - Machinery's Handbook (Thirty-first edition)
+  - Theory of Elasticity (Lamé solution for thick-walled cylinders)
+```
+
 A call to `unit_convert` with a torque-to-energy request fails safely:
 
 ```text
@@ -169,9 +191,10 @@ Use a unit of the same quantity.
 The test suite is deterministic and offline.
 It covers the engines, the unit layer, the database, and the tools.
 
-- 98 tests across 10 files.
+- 109 tests across 11 files.
 - All tests pass on Node 22 and Node 24.
 - The CI workflow runs typecheck, tests, build, demo, and a package check.
+- The CI workflow verifies that the CLI tool list pipes to standard output.
 
 Run `npm test` to reproduce the results.
 
@@ -184,6 +207,8 @@ Run `npm test` to reproduce the results.
 - The critical speed is a first-mode approximation.
 - The spring design covers static round-wire springs only.
   It does not estimate fatigue life for cyclic loads.
+- The press-fit theory assumes elastic material behavior and uniform friction.
+  It does not model residual stress after yield.
 - The built-in SQLite module of Node.js is still experimental.
 
 Check the cited sources for exact values.
@@ -197,11 +222,12 @@ Each release stays useful on its own.
 
 - Helical compression spring design.
   The `spring_design` tool reports the spring rate, the shear stress, and the safety factor.
+- Press and shrink fit analysis.
+  The `interference_fit` tool reports the interface pressure, the hoop stresses, and the friction capacity.
 
 ### Remaining
 
 - Add fatigue analysis for cyclic loads.
-- Add press-fit and interference-fit calculators.
 - Add more unit categories, including viscosity and thermal conductivity.
 - Add HTTP transport.
 - Add a catalog of ISO and DIN standard sections.

data/references.json

@@ -54,5 +54,12 @@
     "edition": "Any standard university text",
     "section": "Critical speed of a uniform simply supported shaft",
     "note": "Gives the first lateral critical speed for a uniform shaft."
+  },
+  "lame-cylinders": {
+    "title": "Theory of Elasticity",
+    "source": "Timoshenko and Goodier, Lamé solution for thick-walled cylinders",
+    "edition": "Any standard university text",
+    "section": "Thick-walled cylinders under internal and external pressure",
+    "note": "Provides the interface pressure and the stress state of a press or shrink fit."
   }
 }

docs/integration.md

@@ -41,11 +41,11 @@ Engineer MCP grows in independent releases. Each release stays useful on its own
 ### Complete
 
 - Helical compression spring design. The `spring_design` tool computes the spring rate, the shear stress, and the safety factor.
+- Press and shrink fit analysis. The `interference_fit` tool computes the interface pressure, the hoop stresses, and the friction capacity.
 
 ### Remaining
 
 - Add fatigue analysis for cyclic loads.
-- Add press-fit and interference-fit calculators.
 - Add more unit categories, including viscosity and thermal conductivity.
 - Add HTTP transport in addition to stdio.
 - Add a catalog of ISO and DIN standard sections.

docs/mcp-tools.md

@@ -158,6 +158,56 @@ Inputs:
 
 The converter rejects mismatched dimensions and mismatched quantity categories. For example, it rejects a torque-to-energy conversion.
 
+## interference_fit
+
+Compute the interface pressure, hoop stresses, and friction capacity of a press or shrink fit.
+
+The tool uses the Lamé solution for thick-walled cylinders.
+The diametral interference drives a uniform contact pressure at the interface.
+The fit can be a press fit or a shrink fit. The math is the same.
+
+Inputs:
+
+- `interfaceRadius`: interface radius in metres.
+- `hubOuterRadius`: outer radius of the hub in metres.
+- `shaftInnerRadius`: inner radius of the shaft in metres. The default is zero for a solid shaft.
+- `interference`: diametral interference in metres.
+- `length`: axial length of the joint in metres.
+- `frictionCoefficient`: friction of the interface. The default is `0.15`.
+- `shaftElasticModulus` and `shaftPoissonRatio`: shaft material. Poisson ratio defaults to `0.3`.
+- `shaftYieldStrength`: shaft yield strength in pascals. It enables the shaft safety factor.
+- `hubElasticModulus` and `hubPoissonRatio`: hub material. Poisson ratio defaults to `0.3`.
+- `hubYieldStrength`: hub yield strength in pascals. It enables the hub safety factor.
+- `requiredTorque`: required torque in newton metres. It enables the torque safety factor.
+
+Outputs:
+
+- `interfacePressure`: contact pressure at the interface.
+- `hubTangentialStress`: hoop stress at the hub bore.
+- `shaftTangentialStress`: hoop stress in the shaft. A hollow shaft peaks at its bore.
+- `axialForceCapacity` and `torqueCapacity`: friction limits of the joint.
+- `shaftSafetyFactor`, `hubSafetyFactor`, and `torqueSafetyFactor`: available margins.
+- The envelope `safetyFactor` is the governing margin. It is the lowest of the three.
+
+The tool warns when a member exceeds its yield strength.
+It warns when the torque capacity is below the required torque.
+
+Example:
+
+```json
+{
+  "interfaceRadius": 0.025,
+  "hubOuterRadius": 0.05,
+  "interference": 0.00005,
+  "length": 0.05,
+  "shaftElasticModulus": 207000000000,
+  "shaftYieldStrength": 300000000,
+  "hubElasticModulus": 207000000000,
+  "hubYieldStrength": 300000000,
+  "requiredTorque": 1000
+}
+```
+
 ## material_lookup
 
 Look up mechanical properties of common engineering materials.