{"openapi":"3.1.0","info":{"title":"Press Fit API","version":"1.0.0","description":"Interference (press and shrink) fit engineering maths as an API, computed locally and deterministically from the Lamé thick-wall equations — the contact-pressure, holding-capacity and assembly-temperature numbers a mechanical designer or machinist sizes a shaft-and-hub joint with. The pressure endpoint gives the contact pressure that builds at the interface from the diametral interference, the shaft and hub diameters and the elastic modulus, plus the tensile hoop stress at the hub bore — the highest stress in the joint, which a thin hub can split if it exceeds the yield: a 50 mm solid steel shaft in a 100 mm hub with 0.05 mm interference makes about 75 MPa of contact pressure and 125 MPa of bore hoop stress, and doubling the interference doubles the pressure. The holding endpoint turns that pressure into the axial push-out force and the transmissible torque through the friction at the interface (force = pressure × contact area × friction, torque = force × shaft radius), the figures that decide whether the joint slips under load. The assembly-temperature endpoint gives the heating (hub) or cooling (shaft) temperature change for a shrink fit — ΔT = (interference + clearance) ÷ (α × diameter) — so the part slides on freely and grips as it returns to temperature. Everything is computed locally and deterministically, so it is instant and private. Ideal for mechanical-design and machine-building tools, manufacturing and CAD utilities, and engineering calculators. Pure local computation — no key, no third-party service, instant. Same-material Lamé estimates — verify against the material yield with a safety factor. 3 compute endpoints. For thin-wall pressure-vessel stress use a pressure-vessel API.","contact":{"name":"PremiumApi","url":"https://www.oanor.com/by/premiumapi"}},"servers":[{"url":"https://api.oanor.com/pressfit-api","description":"oanor gateway"}],"tags":[{"name":"Fit"},{"name":"Meta"}],"components":{"securitySchemes":{"oanorKey":{"type":"apiKey","in":"header","name":"x-oanor-key","description":"Get your key at https://www.oanor.com/developer/keys"}}},"security":[{"oanorKey":[]}],"paths":{"/v1/assembly-temperature":{"get":{"operationId":"get_v1_assembly_temperature","tags":["Fit"],"summary":"Shrink-fit assembly temperature","description":"","parameters":[{"name":"interference_mm","in":"query","required":true,"description":"Diametral interference (mm)","schema":{"type":"string"},"example":"0.05"},{"name":"shaft_dia_mm","in":"query","required":true,"description":"Shaft diameter (mm)","schema":{"type":"string"},"example":"50"},{"name":"assembly_clearance_mm","in":"query","required":false,"description":"Extra clearance (mm, default 0)","schema":{"type":"string"},"example":"0.02"},{"name":"alpha_per_k","in":"query","required":false,"description":"Thermal expansion coeff (/K, default 11.7e-6)","schema":{"type":"string"},"example":"0.0000117"},{"name":"start_temp_c","in":"query","required":false,"description":"Starting temperature (°C, default 20)","schema":{"type":"string"},"example":"20"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Heat the hub (or chill the shaft) so it expands past the interference plus a little assembly clearance, then it slides on freely and grips as it returns to temperature: ΔT = (interference + clearance) ÷ (α · diameter). Steel α ≈ 11.7×10⁻⁶/K. Heating the hub is usual (an oven or induction); chilling the shaft with dry ice or liquid nitrogen suits delicate or already-assembled parts. Mind material temper limits when heating.","inputs":{"alpha_per_k":1.17e-5,"shaft_dia_mm":50,"start_temp_c":20,"interference_mm":0.05,"assembly_clearance_mm":0.02},"required_delta_t_c":119.7,"hub_heating_target_c":139.7,"shaft_cooling_target_c":-99.7},"meta":{"timestamp":"2026-06-06T23:53:53.549Z","request_id":"96b17e72-4eed-4f2a-a55a-e1b3a4ba5b6b"},"status":"ok","message":"Assembly temperature","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/holding":{"get":{"operationId":"get_v1_holding","tags":["Fit"],"summary":"Axial holding force and torque","description":"","parameters":[{"name":"contact_pressure_mpa","in":"query","required":true,"description":"Contact pressure (MPa)","schema":{"type":"string"},"example":"75"},{"name":"shaft_dia_mm","in":"query","required":true,"description":"Shaft diameter (mm)","schema":{"type":"string"},"example":"50"},{"name":"engagement_length_mm","in":"query","required":true,"description":"Engagement length (mm)","schema":{"type":"string"},"example":"40"},{"name":"friction_coeff","in":"query","required":false,"description":"Friction coefficient (default 0.12)","schema":{"type":"string"},"example":"0.12"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Friction at the squeezed interface resists pull-out and twist: axial force = pressure × contact area × friction, and torque = that force × the shaft radius. The friction coefficient for clean dry steel is ~0.1–0.15 (oil lowers it, so press fits are best assembled dry). Longer engagement and higher pressure raise the holding capacity; design with a safety factor over the working load.","inputs":{"shaft_dia_mm":50,"friction_coeff":0.12,"contact_pressure_mpa":75,"engagement_length_mm":40},"contact_area_mm2":6283.2,"torque_capacity_nm":1413.7,"axial_holding_force_n":56549},"meta":{"timestamp":"2026-06-06T23:53:53.637Z","request_id":"5b687930-972a-4f47-8e16-bbb64fd2a0ab"},"status":"ok","message":"Holding force","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/pressure":{"get":{"operationId":"get_v1_pressure","tags":["Fit"],"summary":"Contact pressure and hub hoop stress","description":"","parameters":[{"name":"interference_mm","in":"query","required":true,"description":"Diametral interference (mm)","schema":{"type":"string"},"example":"0.05"},{"name":"shaft_dia_mm","in":"query","required":true,"description":"Nominal interface diameter (mm)","schema":{"type":"string"},"example":"50"},{"name":"hub_outer_dia_mm","in":"query","required":true,"description":"Hub outside diameter (mm)","schema":{"type":"string"},"example":"100"},{"name":"shaft_bore_dia_mm","in":"query","required":false,"description":"Shaft bore (mm, 0=solid)","schema":{"type":"string"},"example":"0"},{"name":"youngs_modulus_gpa","in":"query","required":false,"description":"Young's modulus (GPa, default 200)","schema":{"type":"string"},"example":"200"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"The interference squeezes the parts and a contact pressure builds at the interface, from the Lamé thick-wall equations (same material both parts). The hub bore sees the highest stress — a tensile hoop stress p·(D²+d²)/(D²−d²) — so a thin hub can yield or split; keep it below the material yield with a safety margin. Double the interference and you double the pressure. A solid shaft gives a higher pressure than a hollow one.","inputs":{"shaft_dia_mm":50,"interference_mm":0.05,"hub_outer_dia_mm":100,"shaft_bore_dia_mm":0,"youngs_modulus_gpa":200},"contact_pressure_mpa":75,"hub_bore_hoop_stress_mpa":125},"meta":{"timestamp":"2026-06-06T23:53:53.733Z","request_id":"07d131ea-cf18-4892-95d1-3b3a8f9bef40"},"status":"ok","message":"Contact pressure","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/meta":{"get":{"operationId":"get_v1_meta","tags":["Meta"],"summary":"Spec","description":"","parameters":[],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"notes":"Metric (mm, MPa, N, N·m, °C). Lamé same-material: p from interference; F = p·πdL·μ, T = F·d/2; ΔT = (interference+clearance)/(α·d). Solid steel shaft assumed by default. For thin-wall vessel stress use a pressure-vessel API.","service":"pressfit-api","endpoints":{"GET /v1/meta":"This document.","GET /v1/holding":"Axial holding force and torque from the contact pressure.","GET /v1/pressure":"Contact pressure and hub bore hoop stress from the interference.","GET /v1/assembly-temperature":"Heating/cooling temperature to assemble a shrink fit."},"description":"Interference (press/shrink) fit maths: contact pressure and hub stress, holding force and torque, and the shrink-fit assembly temperature."},"meta":{"timestamp":"2026-06-06T23:53:53.825Z","request_id":"70d4b453-6748-4a6b-8983-339ebbe2fb58"},"status":"ok","message":"Meta","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}}},"x-oanor-pricing":[{"slug":"free","name":"Free","price_cents_month":0,"monthly_call_quota":4200,"rps_limit":2,"hard_limit":true},{"slug":"starter","name":"Starter","price_cents_month":1330,"monthly_call_quota":47000,"rps_limit":6,"hard_limit":true},{"slug":"pro","name":"Pro","price_cents_month":4050,"monthly_call_quota":205000,"rps_limit":15,"hard_limit":true},{"slug":"mega","name":"Mega","price_cents_month":12400,"monthly_call_quota":1090000,"rps_limit":40,"hard_limit":true}],"x-oanor-marketplace-url":"https://www.oanor.com/api/pressfit-api"}