{ "version": "2026-10-20", "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.", "slug": "nema-8-stepper", "name": "NEMA 8 stepper motor: 20.2 mm face, 16 mm hole pattern", "kind": "hardware", "category": "Electronics", "group": "Motors", "year": null, "question": "What are the NEMA 8 stepper motor dimensions?", "tags": [ "stepper", "nema", "nema 8", "motor", "motor envelope", "stirling" ], "aliases": [ "nema 8", "nema8", "nema 8 dimensions", "nema 8 mounting holes", "nema 8 hole pattern", "nema 8 stepper step", "nema 8 stl" ], "overall_mm": { "length": null, "width": null, "height": null }, "official_cad": false, "xem_status": "free-files", "les": false, "free_files": 2, "url": "https://xemstudio.com/objects/nema-8-stepper/", "sheet_txt": "https://xemstudio.com/objects/nema-8-stepper/sheet.txt", "sheet": { "basis": "NEMA ICS 16 frame size 8 (face and mounting-hole pattern); pilot boss and shaft as commonly supplied; body length varies with torque. Envelope only: the outside of the motor. The windings, rotor and bearings inside are not drawn.", "overall_mm": { "length": null, "width": null, "height": null }, "notes": [ "Envelope only: the outside of the motor. The windings, rotor and bearings inside are not drawn.", "NEMA 8 is a 0.8 in face: 20.2 mm square, with chamfered corners. The face and hole pattern are the standard; the body length is the maker's.", "Four M2 tapped holes on a 16 mm square, drawn as plain bores at the thread's major diameter (Ø2) 8 mm deep.", "Pilot boss Ø15 × 1.5; shaft Ø4 × 10 from the boss.", "Files: 30, 38 mm bodies. Leads and connector are not drawn.", "In DIY Stirling builds, a stepper turned by the engine is used as a two-phase generator; each coil pair gives AC that is rectified for a load." ], "table": { "columns": [ "feature", "mm" ], "rows": [ [ "face", "20.2 × 20.2" ], [ "hole pattern", "16 × 16" ], [ "holes", "4 × M2 tapped" ], [ "pilot boss", "Ø15 × 1.5" ], [ "shaft", "Ø4 × 10" ], [ "body lengths drawn", "30, 38" ] ] } }, "sheet_text": "NEMA 8 stepper motor: 20.2 mm face, 16 mm hole pattern — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/nema-8-stepper/ (CC BY 4.0)\nBasis: NEMA ICS 16 frame size 8 (face and mounting-hole pattern); pilot boss and shaft as commonly supplied; body length varies with torque. Envelope only: the outside of the motor. The windings, rotor and bearings inside are not drawn.\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Envelope only: the outside of the motor. The windings, rotor and bearings inside are not drawn.\n- NEMA 8 is a 0.8 in face: 20.2 mm square, with chamfered corners. The face and hole pattern are the standard; the body length is the maker's.\n- Four M2 tapped holes on a 16 mm square, drawn as plain bores at the thread's major diameter (Ø2) 8 mm deep.\n- Pilot boss Ø15 × 1.5; shaft Ø4 × 10 from the boss.\n- Files: 30, 38 mm bodies. Leads and connector are not drawn.\n- In DIY Stirling builds, a stepper turned by the engine is used as a two-phase generator; each coil pair gives AC that is rectified for a load.\n\nfeature mm\nface 20.2 × 20.2\nhole pattern 16 × 16\nholes 4 × M2 tapped\npilot boss Ø15 × 1.5\nshaft Ø4 × 10\nbody lengths drawn 30, 38\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Stepper motor — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stepper_motor\n- NEMA: ICS 16 motion/position control motors and controls — PDF — NEMA standard, purchase — https://www.nema.org/standards/view/motion-position-control-motors-controls-and-feedback-devices\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 2 parts): https://xemstudio.com/files/hardware/nema-8-stepper/index.json\nAPI: https://xemstudio.com/api/geometry?object=nema-8-stepper\n", "sources": [ { "publisher": "Wikipedia", "title": "Stepper motor", "url": "https://en.wikipedia.org/wiki/Stepper_motor", "formats": [ "web" ], "license": "CC BY-SA 4.0 (text)", "license_verified": true, "hosted": false }, { "publisher": "NEMA", "title": "ICS 16 motion/position control motors and controls", "url": "https://www.nema.org/standards/view/motion-position-control-motors-controls-and-feedback-devices", "formats": [ "PDF" ], "license": "NEMA standard, purchase", "license_verified": true, "hosted": false } ], "xem": { "status": "free-files", "sheet_free": true, "mesh_price_usd": null, "step_price_usd": null, "tolerance_mm": null }, "related": [ "nema-11-stepper", "nema-14-stepper", "shaft-couplers", "socket-head-cap-screws-metric", "gt2-pulleys" ], "fits": [ { "role": "Connects to", "items": [ { "slug": "socket-head-cap-screws-metric", "why": "four M2 into the face" } ] }, { "role": "Alternatives", "items": [ { "slug": "nema-11-stepper", "why": "NEMA 11 frame" }, { "slug": "nema-14-stepper", "why": "NEMA 14 frame" } ] } ], "dimensions": "exact (nominal, no printing tolerance)", "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.", "mating": [ { "feature": "pilot boss", "exact": "Ø15 / 22 / 22 / 38.1 / 73", "mates": "mount pilot bore", "fit": "slide", "files": "nema" }, { "feature": "shaft", "exact": "Ø4 / 5 / 5 / 6.35 / 14", "mates": "coupler or pulley bore", "fit": "slide", "files": "nema" }, { "feature": "mount holes", "exact": "M2 / M2.5 / M3 tapped, Ø5.1 / Ø5.5 through", "mates": "mount screws", "fit": "designed", "files": "nema" } ], "fit_classes": { "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.", "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.", "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.", "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.", "clamp": "split part that closes on the mating part with screws: make it at size.", "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change." }, "faq": [ { "q": "What is the NEMA 8 hole pattern?", "a": "4 × M2 tapped on a 16 × 16 mm square, on a 20.2 mm face." }, { "q": "What is the NEMA 8 shaft size?", "a": "Ø4 mm as commonly supplied (10 mm out from the Ø15 pilot boss)." }, { "q": "How long is a NEMA 8 stepper?", "a": "The standard fixes the face, not the length. Common bodies: 30, 38 mm; longer bodies give more torque." } ], "files_license": null, "offers": [ { "file": "nema8-30", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-30.step", "stl": "https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-30.stl", "note": "NEMA 8 envelope, 30 mm body, 16.0 mm hole pattern (M2 tapped), Ø4.0 shaft" }, { "file": "nema8-38", "formats": [ "step", "stl" ], "price_usd": 0, "license": "CC BY 4.0 (Xem Studio)", "step": "https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-38.step", "stl": "https://xemstudio.com/files/hardware/nema-steppers-8-to-34/nema8-38.stl", "note": "NEMA 8 envelope, 38 mm body, 16.0 mm hole pattern (M2 tapped), Ø4.0 shaft" } ], "markdown": "https://xemstudio.com/objects/nema-8-stepper/index.md" }