54mm x 46mm x 20mm Arc Magnets Neodymium Magnet Checker
First screen solves the tool intent: input your geometry and operating constraints, then get a deterministic fit verdict with next action. Deeper sections provide evidence, boundary conditions, tradeoffs, and procurement-risk controls for this exact dimension query.
Published: April 18, 2026
Evidence update: April 18, 2026 (stage1b refresh: USGS + ECHA + EUR-Lex + Henkel)
Distinct angle: this page focuses on one size cluster (54/46/20) and turns listing-level intent into engineering and sourcing decisions in one URL.
Tool Layer: Run The Fit Checker
Input geometry and operating assumptions, then get interpreted output, uncertainty, and a direct next step.
Input ranges are enforced in the checker. Segment count and Max RPM must be integers.
N45H: max screening temperature 120 C. H-class option often selected for moderate-speed motor environments.
Empty state
Run checker to generate geometry fit, thermal margin, retention margin, and an action-oriented verdict.
Report Summary: Conclusions, Numbers, Fit/Unfit
This layer translates calculator output into decisions with boundaries and audience fit guidance.
1) Tool-first intent is size-specific
Public listings for this exact SKU publish dimensions, grade, polarity split, and max temperature, so users expect an immediate fit/readiness answer, not generic magnet theory [S1][S2].
2) Thermal and retention are the two critical failure gates
A “dimension match” alone does not imply readiness. Thermal margin and retention margin determine practical reliability. This page keeps both as explicit screening gates with disclosed evidence and limits [S5].
3) Grade choice is a tradeoff, not a one-way upgrade
SH/SmCo paths can reduce heat risk but may increase cost, lead time, and process complexity.
4) Procurement volatility should be modeled early
USGS 2026 reports NdPr oxide average moved from 55 to 69 $/kg (2024 to 2025) and U.S. net import reliance rose from 53% to 67%, so re-quote and fallback gates should be contract-level, not ad hoc [S6].
5) EU compliance is a shipment gate, not post-PO paperwork
Candidate List currently shows 253 entries and REACH/RoHS obligations trigger from explicit thresholds (>0.1% w/w and related notification windows), so document ownership must be locked before shipment planning [S9][S10][S11].
Geometry
Coverage window
Thermal margin
Retention buffer
| Profile | Fit | Reason |
|---|---|---|
| Replacement job with known duty cycle and compatible pole layout | Suitable | Dimension-specific stock path plus checker can quickly validate geometry and boundary conditions. |
| High-temperature continuous-duty traction case | Conditional | Often needs SH/SmCo path and stronger retention strategy beyond stock assumptions. |
| Cost-first project with weak process control | Not suitable | Without tolerance, curing, and QC control, failure risk can exceed savings from a cheaper listing. |
Methodology And Evidence
Tool logic, source chain, and known unknowns are disclosed so users can judge confidence boundaries.
- Parse and validate geometry/operating inputs with explicit ranges.
- Compute geometric metrics (thickness, arc length, chord, coverage).
- Compute thermal and retention screening metrics with grade/safety assumptions.
- Output verdict, uncertainty, and minimum executable next action.
Evidence is layered from direct size-intent listings to material and retention references, then supply-risk context. Items without strong public evidence are explicitly marked as unknown.
Known unknowns
- Public listing data can show grade and polarity direction, but usually omits full tolerance stack, coating-thickness distribution, and lot-acceptance method.
- No reliable public retention-fatigue dataset currently covers this exact 54/46/20 geometry across full RPM-temperature-life combinations.
- Lead-time and MOQ volatility are region and quarter dependent.
| ID | Source | Key data | Context | Date marker |
|---|---|---|---|---|
| S1 | Apex Magnets product listing (54 x 46 x 20 mm arc set) | Listing shows 54x46x20 dimensions, N45H grade, max operating temperature 248F, Ni coating, and 20-piece set (10N + 10S). | Primary evidence that this exact dimension query is transactional and size-specific, with polarity orientation visible. | Listing accessed on April 18, 2026 |
| S2 | Made-in-China listing for 54 x 46 x 20 mm neodymium arc magnets | Listing shows 54x46x20 size, N45H, Ni coating, 120 C max operating temperature, MOQ 1 piece, and 2-5 day lead-time signal. | Supports procurement-intent, supplier-comparison, and public-field-coverage checks. | Listing accessed on April 18, 2026 |
| S3 | Arnold Magnetic Technologies NdFeB grade reference | Public grade table distinguishes H/SH/UH classes and shows thermal-performance tradeoffs across NdFeB grades. | Used for grade-boundary and thermal-margin interpretation. | Reference accessed on April 18, 2026 |
| S4 | Arnold RECOMA SmCo reference | Sm2Co17 table lists high-temperature operating capability relative to NdFeB classes. | Supports high-temperature fallback comparison in this page. | Reference accessed on April 18, 2026 |
| S5 | Henkel LOCTITE 648 technical data sheet | TDS reports ISO 10123 compressive shear values (steel pins/collars): 13.5 N/mm2 at 15 min and 31 N/mm2 at 72 h, with cure-speed/gap sensitivity. | Used to calibrate retention-screening assumptions and to disclose lab-test geometry limits. | TDS May 2021, accessed on April 18, 2026 |
| S6 | USGS Mineral Commodity Summaries 2026 - Rare Earths | USGS reports Nd oxide 56->73 $/kg (2024->2025), NdPr oxide 55->69 $/kg, import compounds 8,120->21,000 t, and net import reliance 53%->67%. | Used in procurement volatility and risk-mitigation sections. | USGS report published in February 2026 |
| S7 | NEMA MG-1 Part 12 | NEMA guidance notes best performance when terminal voltage unbalance stays within 1%. | Used as a downstream motor-validation boundary after magnet selection screening. | Watermark PDF accessed on April 18, 2026 |
| S8 | Apex listing cross-channel ecommerce references | Public retail channel mirrors the same size-intent and suggests buyers compare stock, lead time, and set completeness (e.g., spare segments). | Supports practical buying checklist and anti-misfit recommendations. | Cross-channel scan completed on April 18, 2026 |
| S9 | ECHA Candidate List table | Candidate List page shows 253 entries in total; latest inclusion date displayed as 04-Feb-2026. | Used to set REACH/SVHC volatility checks for EU-bound magnet procurement. | ECHA page accessed on April 18, 2026 |
| S10 | ECHA Candidate List obligations | For articles >0.1% w/w SVHC, suppliers must communicate safe-use info; consumer requests require response within 45 days; producer/importer notification applies above 0.1% w/w and >1 t/y, due within 6 months. | Used in compliance-gate and RFQ document-check sections. | ECHA page accessed on April 18, 2026 |
| S11 | EUR-Lex Commission Delegated Directive (EU) 2015/863 | RoHS Annex II lists ten restricted substances with limits 0.1% w/w (most) and 0.01% for cadmium in homogeneous material. | Used to define baseline RoHS evidence pack requirements for EU deliveries. | Directive text accessed on April 18, 2026 |
| S12 | USGS Mineral Commodity Summaries 2026 - Rare Earths (Heavy) | USGS reports heavy rare-earth import reliance at 100% and notes April 2025 export-control tightening followed by partial suspension in November 2025. | Used to frame heavy-rare-earth shock scenarios in contingency sourcing plans. | USGS report published in February 2026 |
| Metric | 2024 | 2025 | Decision impact | Source |
|---|---|---|---|---|
| Neodymium oxide average price | 56 $/kg | 73 $/kg | Quote validity windows should be shorter for Nd-heavy options. | S6 |
| NdPr oxide average price | 55 $/kg | 69 $/kg | Fallback grade and re-quote trigger clauses should be pre-defined. | S6 |
| U.S. imports of rare-earth compounds | 8,120 t | 21,000 t | Lead-time assumptions should include dependency on external refined supply. | S6 |
| Net import reliance (compounds + metals) | 53% | 67% | Single-source contracts are more exposed to policy and logistics shocks. | S6 |
| Gate | Threshold | Deadline / scope | Procurement action | Source |
|---|---|---|---|---|
| RoHS restricted substances in homogeneous material | 0.1% w/w for Pb/Hg/Cr6+/PBB/PBDE/DEHP/BBP/DBP/DIBP; 0.01% for Cd | EU EEE market access baseline | Request supplier declaration explicitly mapped to Annex II substances. | S11 |
| REACH Article 33 communication | SVHC in article >0.1% w/w | Consumer requests must be answered within 45 days | Prepare customer-facing safe-use response template before shipment. | S10 |
| REACH Article 7(2) notification to ECHA | SVHC >0.1% w/w and >1 tonne/year per producer or importer | Submit no later than 6 months after list inclusion | Assign importer-of-record responsibility and calendar legal deadline. | S10 |
| SCIP database submission (WFD route) | Article contains Candidate List substance >0.1% w/w | Applies when placing article on EU market | Confirm SCIP submission owner and evidence archive before EU dispatch. | S10 |
| Gate | Current rule | Evidence basis | Limitation | Minimum next action |
|---|---|---|---|---|
| Thermal margin gate | Flag when thermal margin < 15 C | Grade temperature classes from NdFeB/SmCo references plus duty uncertainty buffer [S3][S4]. | No universal public standard defines 15 C as a pass/fail threshold for every motor architecture. | Treat as screening trigger; validate with duty-cycle thermal test or calibrated model. |
| Retention margin gate | Flag when retention margin < 3 MPa | Derived from adhesive baseline and ISO 10123 steel pin/collar shear data in LOCTITE 648 TDS [S5]. | TDS geometry and curing setup differ from coated arc magnets in production assemblies. | Run process-specific coupon/rotor tests before reliability sign-off. |
| Coverage-ratio gate | Preferred window 0.85-1.10 | Geometric fit heuristic based on arc angle versus pole pitch relation in this checker. | No open standard maps one ratio window to all slot/pole combinations and harmonic targets. | Verify with electromagnetic simulation or measured back-EMF/cogging data. |
| High tip-speed escalation | Escalate when tip speed > 80 m/s | Conservative internal trigger to force mechanical-retention review at higher centrifugal stress. | No reliable public dataset currently covers fatigue-retention limits for this exact 54/46/20 geometry across full life cycles. | Use sleeve/groove retention path and run overspeed plus thermal cycling tests. |
Comparison And Tradeoffs
Alternative options are compared with explicit tradeoffs instead of one-way recommendation language.
| Option | Temperature path | Procurement profile | Main risk | Best for |
|---|---|---|---|---|
| Stock N45H 54x46x20 arc set (18+2 style package) | Moderate thermal window (~120 C class) | Fastest to buy when stock exists; lowest qualification overhead | Can lose margin in high-heat duty if hotspot assumptions are optimistic | Prototype turns and replacement jobs with controlled duty cycle |
| Custom N48SH / N52SH 54x46x20 | Higher thermal class (~150 C) with stronger coercivity path | Higher MOQ and quoting cycle; requires drawing/tolerance agreement | Higher cost and potential lead-time extension in volatile Nd price windows | Production programs needing stronger thermal confidence |
| Sm2Co17 custom arc segment | High-temperature capability (up to ~300 C class) | Specialized vendors and longer machining/inspection cycle | Lower magnetic loading and higher material brittleness/cost | High-heat environments where NdFeB thermal margin is persistently negative |
| Geometry fallback (same grade, lower RPM / sleeve / improved cooling) | Depends on system thermal redesign | Can keep existing grade if mechanical/thermal redesign is feasible | Program delay if redesign is discovered late | Projects with fixed BOM contracts but flexible rotor/mechanical design |
Assumption: Need exact 54x46x20 size quickly; thermal and speed profile are unchanged from validated baseline.
Recommended path: Use stock-grade path, run checker, require retention margin >= 3 MPa and thermal margin >= 15 C before order.
Expected outcome: Shortest turnaround with bounded risk if operating envelope remains unchanged.
Assumption: Ambient rises from 35 C to 60 C, and duty cycle extends to near-continuous operation.
Recommended path: Switch to high-temp preset, evaluate SH/SmCo branch, and verify whether cooling or grade change is lower total risk.
Expected outcome: Avoids underestimating demagnetization and adhesive aging risk in high-heat use.
Assumption: RPM target increases while OD/ID/length remain 54/46/20.
Recommended path: Run high-speed preset, focus on retention demand and coverage ratio, then decide sleeve vs RPM rollback.
Expected outcome: Prevents hidden centrifugal retention failure after prototype pass.
Assumption: Program needs cost reduction without missing delivery schedule in a volatile rare-earth market.
Recommended path: Use comparison matrix: grade fallback vs geometry redesign; lock re-quote thresholds and dual-source backup.
Expected outcome: Turns market volatility into explicit decision gates instead of last-minute firefighting.
Risk Matrix And Mitigation
Misuse risk, cost risk, and scenario mismatch are presented with concrete triggers and actions.
Prioritize rows with high impact + medium/high probability before any PO release.
Rare-earth pricing and policy shocks are treated as schedule-risk inputs, not just purchasing data. Use contract-level re-quote and fallback clauses before pilot freeze. USGS 2026 records both 2025 price moves and export-control volatility signals [S6][S12].
| Risk | Probability | Impact | Trigger | Mitigation |
|---|---|---|---|---|
| Thermal overload causes irreversible flux loss | Medium | High | Thermal margin < 15 C in peak duty or seasonal high ambient | Upgrade grade class, reduce hotspot through cooling path changes, and validate with worst-case thermal profile. |
| Adhesive-only retention margin is insufficient at target RPM | Medium | High | Retention margin < 3 MPa after safety factor | Add mechanical retention (sleeve/groove), increase cured shear baseline, or reduce tip speed. |
| Segment count / arc angle mismatch creates flux ripple or assembly gap | Medium | Medium | Coverage ratio outside 0.85-1.10 screening window | Recalculate pole pitch, adjust arc angle, and verify assembly stack-up tolerances before PO release. |
| Procurement shock from rare-earth price and policy changes | High | Medium | Nd/NdPr market jump or export-policy updates during RFQ cycle | Use dual-source qualification, re-quote trigger clauses, and grade fallback paths in the sourcing plan. |
| False confidence from incomplete public listing data | High | Medium | Missing tolerance stack, coating-thickness distribution, or lot-level retention-test evidence | Force critical spec checklist: tolerance, coating, magnetization orientation, and incoming QC method. |
| EU shipment risk from incomplete RoHS/REACH evidence | Medium | High | Supplier quote lacks RoHS substance declaration and SVHC article statement for the latest Candidate List cycle | Gate PO release on RoHS Annex II declaration, REACH Article 33 communication template, and SVHC/SCIP responsibility confirmation. |
FAQ By Decision Intent
Grouped FAQ keeps the page actionable for sizing, reliability, and procurement decisions.
Minimum package: OD/ID/length, arc angle, segment count, magnetization orientation, coating, RPM envelope, and hotspot estimate.
If thermal margin < 15 C or retention margin < 3 MPa, mark it as blocker in your request so fallback options are prioritized.
Include target RPM and duty cycle; these two inputs drive retention stress and decision branch selection.
Attach current supplier specs if available so we can run a direct delta check instead of generic recommendations.
Need adjacent context before RFQ?