Production run proofing is the last chance to catch a mistake before it becomes a scrapped part. Every deep hole drilling setup should be proved before the first production part is drilled. The cost of proofing is a few minutes of inspection time; the cost of a proofing failure is hours of rework or a scrapped part worth hundreds or thousands of dollars.
Pre-Proofing Setup Verification
Setup Checklist
| Item | Verification | Method | Sign-Off |
|---|
| Process sheet available and current | Check revision, part number match | Visual | Setup technician |
| Fixture installed and aligned | Alignment within 0.01 mm per 300 mm | Test bar + indicator | Setup technician |
| Bushing installed and dimension verified | ID within 0.01 mm of specification | Bore gauge | Setup technician |
| Drill selected per process sheet | Part number matches | Visual — check part number | Setup technician |
| Drill measured and within tolerance | Diameter within ±0.005 mm of spec | Micrometer | Setup technician |
| Drill mounted and runout checked | Runout < 0.015 mm at tip | Dial indicator | Setup technician |
| Coolant type and concentration verified | Per process sheet — 7–9% typical | Refractometer | Setup technician |
| Coolant pressure set per specification | Within ±5% of target | Pressure gauge | Setup technician |
| CNC program loaded and verified | Program number matches traveler | Visual check | Setup technician |
| Spindle warm-up completed | 30-minute warm-up | Timer | Setup technician |
Setup Verification Sign-Off
| Role | Responsibility | Signature |
|---|
| Setup technician | Performs all setup steps per checklist | Required before first article |
| Setup inspector (if required) | Verifies critical setup items | Required for critical setups |
| Operator | Reviews setup before starting run | Required before production |
First-Article Drilling
First-Article Procedure
| Step | Action | Detail |
|---|
| 1 | Verify all setup checklist items are signed off | Do not proceed if any item is unchecked |
| 2 | Start coolant flow | Verify pressure at target |
| 3 | Start spindle warm-up (if not already done) | 30 minutes at operating speed |
| 4 | Drill first test hole | Use the parameters from the process sheet |
| 5 | Monitor drilling parameters | Load, pressure, chip shape — record on traveler |
| 6 | Stop after hole completion | Do not adjust parameters during first article |
| 7 | Retract drill and stop coolant | Normal cycle completion |
| 8 | Remove test piece | Handle carefully — do not damage bore |
First-Article Inspection
| Characteristic | Measurement Tool | Acceptance Criteria | Record |
|---|
| Hole diameter at entry | Bore gauge | Within drawing tolerance | ±0.XXX mm |
| Hole diameter at mid-depth | Bore gauge | Within drawing tolerance | ±0.XXX mm |
| Hole diameter at exit | Bore gauge | Within drawing tolerance | ±0.XXX mm |
| Taper (entry − exit) | Calculated | < 0.02 mm (typical) | 0.XXX mm |
| Surface finish (Ra) | Profilometer | Per drawing — typically < 0.8 µm | X.X µm |
| Hole depth | Depth gauge or CNC position | Within ±1 mm | XXX mm |
| Straightness (if required) | Straightness gauge or CMM | Per drawing | X.XX mm |
| Hole position (if relevant) | CMM | Per drawing | X.XX mm |
First-Article Acceptance
| Result | Action | Follow-up |
|---|
| All characteristics pass | Approve setup for production | Sign traveler, begin production run |
| One characteristic marginal | Evaluate — may accept with engineering approval | Document on traveler |
| One characteristic fails | Investigate root cause, correct, re-test | Document NCR, re-setup, drill new first article |
| Multiple characteristics fail | Reject setup — full re-setup required | Return to setup technician |
Run Monitoring During Proofing
Proofing Run Size
| Production Volume | Proofing Run Size | Purpose |
|---|
| < 20 parts | 2 parts (first + last) | Verify consistency |
| 20–100 parts | 5 parts (first, 25%, 50%, 75%, last) | Trend detection |
| 100–1,000 parts | 10 parts or 10% (whichever is larger) | Statistical confidence |
| > 1,000 parts | First 20 parts, then per sampling plan | Early problem detection |
Monitoring During Proofing
| Check Point | What to Check | Action if Out of Tolerance |
|---|
| Every part (proofing run) | Diameter at one depth | Stop and investigate |
| Every 5th part | Surface finish | Adjust parameters if trending high |
| Every part | Chip shape | Stop if chip shape changes significantly |
| Continuous | Spindle load | Investigate if load changes > 10% |
| Every part | Coolant pressure | Stop if pressure drops below minimum |
| After each tool change | Runout | Verify before next part |
Documentation Requirements
Proofing Documentation
| Document | Contents | Signed By |
|---|
| Setup checklist | All setup items verified | Setup technician |
| First-article inspection report | All hole characteristics measured | Inspector |
| Proofing run log | Parameters, observations, results | Operator |
| Tool usage record | Tool ID, hole count, condition | Operator |
| Approval to run | Authorization to begin production | Supervisor or quality |
Common Proofing Failures
| Failure | Likely Cause | Corrective Action |
|---|
| Diameter oversize on first article | Bushing worn, wrong bushing, tool runout | Check bushing ID, replace if needed, verify runout |
| Diameter undersize | Drill diameter below spec, new bushing tight | Verify drill diameter, check bushing ID |
| Poor surface finish | Coolant issue, dull drill, wrong parameters | Check coolant concentration, replace drill, verify speed/feed |
| Straightness out | Alignment issue, bushing worn, fixture problem | Check alignment, bushing, fixture |
| Chip packing | Coolant pressure low, chip breaker geometry | Check pressure, verify drill geometry |
| Drill walking at entry | Bushing worn or missing, entry feed too high | Install/replace bushing, reduce entry feed |
Transition to Production
| Step | Action | Detail |
|---|
| 1 | Verify all proofing documentation is complete | Traveler, inspection report, tool records |
| 2 | Obtain approval signature | Supervisor or quality representative |
| 3 | Remove proofing test piece from production area | Mark as "Setup Proofing — Not for Delivery" |
| 4 | Begin production run | First production part follows same process as proofing |
| 5 | Reduce inspection frequency to production level | Per sampling plan on process sheet |
FAQ
What is production run proofing in deep hole drilling?
Production run proofing is the systematic verification that a machine setup is correct before production begins. It includes verifying the setup checklist, drilling and inspecting a first article, monitoring a proofing run of several parts, and obtaining approval to begin production. Proofing catches setup errors before they produce scrap.
How many parts should be included in a proofing run?
The proofing run size depends on production volume. For runs under 20 parts, proof 2 parts (first and last). For runs of 20–100 parts, proof 5 parts at intervals (first, 25%, 50%, 75%, last). For runs over 100 parts, proof 10 parts or 10% and use the data to establish initial statistical control. In all cases, the proofing run must be sufficient to detect stability issues.
What is the difference between first-article inspection and production run proofing?
First-article inspection is the measurement of the first part from a setup to verify that all characteristics meet specification. Production run proofing is the broader process that includes first-article inspection plus setup verification, a monitored proofing run, and formal approval to begin production. First-article inspection is one part of proofing; proofing is the complete process.
What happens if a first-article fails inspection?
If the first article fails any characteristic, do not adjust parameters and try again. Investigate the root cause of the failure. Common causes: fixture misalignment, wrong tool, wrong bushing, coolant problem, or CNC program error. Correct the root cause, re-verify the setup, and drill a new first article. Document the failure and corrective action on a non-conformance report.
Who is responsible for approving a production run proofing?
Three roles should sign off: the setup technician (verifies setup is correct), the inspector (verifies first article meets specification), and the supervisor or quality representative (authorizes production to begin). For critical or safety-related parts, customer approval of the first-article report may also be required before production.
Production run proofing is a small investment of time that prevents large losses. Every scrapped part from a setup error could have been prevented by a proper proofing procedure. Make proofing a required step — not an optional extra — for every deep hole drilling setup. This article reflects industry practice as of 2026.
