Roller Chain Engineer Guide

Use this section when reading roller chain results. Roller chain matching is not pitch-only matching; identity, strand count, series, geometry, and strength all matter.

How To Read A Roller Chain Result

1. Confirm the reference chain was resolved correctly.
2. Read class: DROP_IN_FIT, FIT_OR_BETTER, or PENDING_VERIFICATION.
3. Check passed_gates and failed_gates.
4. Review pending_reason if the row is not a direct fit.
5. Check tags for pitch, roller diameter, strand count, series, width, and FB strength.
6. Compare technical snapshot fields for pitch, roller diameter, inner width, strand count, system group, series variant, attachments, and minimum breaking load.
7. Decide whether the result is a direct interchange, controlled upgrade, or evidence-gathering task.

Do

• Do treat DROP_IN_FIT as the strongest direct interchange class.
• Do treat FIT_OR_BETTER as a controlled upgrade, not a casual substitute.
• Do treat PENDING_VERIFICATION as a request for more evidence.
• Do confirm strand count before recommending.
• Do confirm minimum breaking load / FB is not lower than required.
• Do check attachment presence and signature when attachments exist.
• Do explain inferred geometry when data came from standards instead of direct evidence.

Don’t

• Do not match chains by pitch alone.
• Do not ignore strand count.
• Do not cross A-series/B-series/system families unless policy explicitly allows it.
• Do not recommend lower FB strength.
• Do not ignore width gates.
• Do not treat standard-inferred geometry as equally strong as measured/catalog evidence.
• Do not present PENDING_VERIFICATION as a replacement.

Status Next Actions

Status	Engineer action
OK	Read class, gates, strength, geometry, and pending reason.
AMBIGUOUS_MATCHES	Ask for exact chain designation, standard, strand count, attachment details, or catalog evidence.
INPUT_RECHECK_REQUIRED	Resolve conflicting chain code, dimensions, strand count, or system group.
NO_REFERENCE	Request chain designation, pitch, roller diameter, width, strand count, and standard.
ERROR	Do not interpret candidates; retry or escalate.

Tag Next Actions

Tag	What to do next
FB_INSUFFICIENT	Reject or find higher-strength candidate.
STRAND_COUNT_UNKNOWN	Ask for simplex/duplex/triplex or measured strand count.
STRAND_COUNT_MISMATCH	Reject unless the application explicitly changes strand count.
SERIES_VARIANT_INCOMPATIBLE	Do not substitute across incompatible series.
WIDTH_EXCEEDS_TOLERANCE	Check sprocket and clearance envelope; usually blocks fit.
WIDTH_BELOW_REFERENCE	Confirm engagement/support implications before use.
PITCH_MISMATCH	Reject as a chain fit.
ROLLER_DIAMETER_MISMATCH	Reject or verify source data.
UNVERIFIED_SCOPE	Collect stronger product/standard evidence.
LOW_CONFIDENCE_CORE_FIELDS	Recheck extracted dimensions or code.
UPGRADE_NOT_REQUESTED	Do not present upgrade unless user/workflow allows it.
USER_CRITICAL_GEOMETRY_MISSING	Ask for the missing geometry before recommending.
GEOMETRY_INFERRED_FROM_STANDARD	Mark as inferred and request catalog/measured confirmation if critical.

Example Workflow

When a candidate is PENDING_VERIFICATION because strand count is unknown and geometry is inferred:

1. State that the candidate cannot be treated as drop-in yet.
2. Ask for strand count and catalog/measurement evidence.
3. Re-run or re-evaluate after the missing fields are confirmed.
4. Only then decide between direct fit, controlled upgrade, or rejection.

Never Claim

• Never claim fit from pitch alone.
• Never claim FIT_OR_BETTER without explaining what is better and what stayed compatible.
• Never claim inferred standard geometry is confirmed product evidence.