Caster stem types and sizes: threaded stem (3/8-16, 1/2-13, M10, M12), grip ring 7/16 in, expanding adapter, bolt-hole fitting — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/caster-stems-threaded-grip-ring/  (sheet CC BY 4.0)
Basis: One retailer's stem-caster sizing guide (text and spec sheet) and a Blickle bolt-hole datasheet, read in this session; numbers only
Catalog version: 2026-10-20

Sizes: see table below
- A stem caster is held to the equipment by a stem instead of a top plate: a threaded stem screws into a tapped hole or nut, a grip-ring stem presses into a socket, an expanding adapter wedges in a tube. Thread sizes the guide lists: UNC 3/8-16, 1/2-13, 5/8-11, 3/4-10, 1-8; UNF 3/8-24, 1/2-20, 5/8-18; metric M8, M10, M12, M16 (BSF / BSW are mentioned without sizes). Stem lengths are measured from the caster plate or shoulder to the tip.
- Stem diameters printed: 1/4 (.250), 5/16 (.313), 3/8 (.375), 7/16 (.437, grip ring), 1/2 (.500), 5/8 (.625), 3/4 (.750), 7/8 (.875), 1 (1.000) in. The guide says the stem diameter must match the host hole or tube within 1/64 in. It prints no tap-drill, host-hole or socket diameters, so none is given here.
- Grip ring: the guide's table lists 7/16 × 7/8 and 7/16 × 1-7/16 in; its introduction says 7/16 and 1/2 in diameters exist, but 1/2 in is not in its size table. A commonly quoted '7/16 × 1-3/8' size is not on this guide and is not used.
- No file: the shape of a stem fitting (collar, shoulder, grip ring, kingpin) is not defined by published numbers in the sources read. Plate casters are on caster-top-plate-patterns.

stem type  thread / diameter (inch)  UNF (fine)  metric  length  host
threaded stem  UNC 3/8-16, 1/2-13, 5/8-11, 3/4-10, 1-8  UNF 3/8-24, 1/2-20, 5/8-18  M8, M10, M12, M16  1, 1-1/2, 1-3/4, 2 in (from the plate to the tip)  tapped hole in the host; no tap drill printed
grip ring (friction ring) stem  7/16 in diameter (the guide's table; its text also mentions 1/2 in)  —  —  7/8 in or 1-7/16 in; sizes printed 7/16 × 7/8 and 7/16 × 1-7/16  precision-fit socket; no socket size printed
expanding adapter stem  —  —  —  1-1/2 to 2 in compressed  tube ID between the compressed and expanded OD; tube sizes 7/8, 1, 1-1/8, 1-1/4 in (and metric)
plain round stem and square stem  —  —  —  varies by OEM  —
bolt-hole fitting (not a stem)  —  —  Blickle LMDA-TPA 50 and 75: hole Ø10.2 mm, plate Ø41 / Ø55 mm  —  single central bolt

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- CasterHQ: Stem casters sizing guide: stem types, thread sizes, stem lengths, grip ring 7/16 in, expanding adapter tube sizes — web — Retailer guide; numbers only — https://casterhq.com/blogs/caster-university/stem-casters-sizing-guide
- CasterHQ: Stem casters sizing guide spec sheet (PDF) — web — Publisher's page; dimensions are facts — https://casterhq.com/downloads/stem-casters-sizing-guide-spec-sheet
- Blickle (via Raptor Supplies datasheet): LMDA-TPA 50 / 75 castors with central bolt-hole fitting: wheel diameter, total height, plate diameter, bolt hole diameter, offset — web — Maker datasheet; numbers only — https://static.raptorsupplies.com/catalog/product/datasheet/blickle-lmda-tpa-50k-fk.pdf
- McMaster-Carr: Casters (plate, stem, bolt-hole) (free STEP/IGES per part, for your own design use; no redistribution) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution [verify license at link] — https://www.mcmaster.com/products/casters/

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=caster-stems-threaded-grip-ring