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A poorly written RFQ for deep hole drilling services can result in quotes that vary by 300% from the same part, suppliers that cannot actually hold the specified tolerances, and costly engineering change orders after the contract is awarded. The difference between a good RFQ and a bad one is not the amount of information — it is whether the information is the right information.
Deep hole drilling — gun drilling, BTA drilling, trepanning, and skiving and roller burnishing — is a specialized manufacturing process. Standard machining RFQ templates do not capture the specific requirements that determine whether a deep hole drilled part will function correctly.
This article provides a complete RFQ template and best practices specifically for deep hole drilling services, designed for procurement engineers, buyers, and technical professionals who need to source deep hole drilled components.
Why Deep Hole Drilling RFQs Require Special Attention
Deep hole drilling differs from conventional machining in several ways that affect RFQ content:
| Factor | Conventional Machining | Deep Hole Drilling |
|---|---|---|
| Hole L/D ratio | Typically under 5:1 | Commonly 20:1 to 300:1 |
| Coolant system | Standard through-spindle (10–30 bar) | High-pressure (50–200 bar), high-flow, with filtration |
| Tooling | Standard drills and end mills | Specialized gun drills, BTA heads, guide bushings |
| Straightness | Usually not specified | Critical — determined by process and equipment |
| Surface finish | Generally achievable with standard tooling | Requires specific methods (gun drilling, reaming, SRB) |
| Chip evacuation | Gravity or air blast | High-pressure coolant through long passages |
| Equipment | Standard CNC mills and lathes | Dedicated gun drilling or BTA machines |
| Inspection | Standard gauges | Specialized: air gauges, bore microscopes, borescopes |
A general CNC machining RFQ will not tell a deep hole drilling specialist what they need to know. If you omit straightness requirements, coolant access direction, or bore entry conditions, the supplier must guess — and their quote will include contingency pricing for the uncertainty.
Essential Components of a Deep Hole Drilling RFQ
A complete deep hole drilling RFQ package must include standard machining information plus deep-hole-specific technical data. Below is the complete checklist.
Part 1: General Information
| Field | Description | Required? |
|---|---|---|
| RFQ number | Your internal reference number | Yes |
| Date issued | Date of RFQ issuance | Yes |
| Response deadline | Date by which quotes must be submitted | Yes |
| Company name and address | Buyer information | Yes |
| Contact person | Name, email, phone | Yes |
| Shipping terms | Incoterms (FCA, DDP, EXW, etc.) | Yes |
| Payment terms | Net 30, Net 60, etc. | Yes |
| NDA required | Non-disclosure agreement reference | If applicable |
| Estimated annual volume | Quantity per year | Recommended |
| Target price range | Optional — only if known | Optional |
Part 2: Part Identification
| Field | Description | Required? |
|---|---|---|
| Part number | Your part number | Yes |
| Part name | Descriptive name | Yes |
| Revision | Current drawing/model revision | Yes |
| Drawing format | PDF is standard, DWG for some shops | Yes |
| 3D model format | STEP, IGES, Parasolid, or native | Yes |
| Previous supplier | Name if re-sourcing | Recommended |
| Annual quantity | Current and projected | Yes |
Part 3: Deep Hole Drilling Technical Specifications
This is the section unique to deep hole drilling RFQs. Every item here directly affects drilling method selection, tooling cost, and cycle time.
| Specification | Example Entry | Why It Matters |
|---|---|---|
| Hole diameter | φ18.00 mm H8 | Determines drilling method and tool size |
| Hole depth | 1,200 mm | Determines L/D ratio and machine requirement |
| L/D ratio | 66:1 | Signals difficulty — affects method selection |
| Through-hole or blind? | Through-hole | Affects chip evacuation strategy |
| Entry angle to surface | 90° (perpendicular) | Determines entry bushing requirements |
| Exit condition | Flat exit surface | Prevents drill breakout damage |
| Straightness requirement | 0.05 mm per 100 mm | Critical for mating assembly |
| Surface finish (bore) | Ra 0.8 μm | Determines need for secondary finishing |
| Tolerance grade | H7 (+0.021 mm for 18 mm) | Drives tool selection and inspection method |
| Bore concentricity to OD | φ0.10 mm | Determines fixturing approach |
| Drilling direction | From one end or both ends | Affects setup and straightness |
| Pre-existing bore? | Solid bar (no pre-hole) | Different method vs. starting from a tube |
| Cross-holes intersecting bore? | Yes, 2 cross-holes at 200 mm and 400 mm | Affects deburring requirements |
| Coolant access | Coolant from spindle side | Determines machine interface |
| Entry bushing type required | Tungsten carbide guide bushing | Standard for gun drilling |
Tip: When in doubt about whether to include a specification, include it. Suppliers will ignore irrelevant data but cannot quote accurately on missing data.
Part 4: Material Specifications
| Field | Example | Notes |
|---|---|---|
| Material grade | 42CrMo4 (AISI 4140) | Use standard designations |
| Material condition | Q&T to 280–320 HB | Hardness affects drilling parameters |
| Material standard | DIN 17200 or ASTM A29 | Specifies the governing standard |
| Starting form | Solid bar, seamless tube, forged blank | Affects rough drilling method |
| OD condition | Turned, black bar, forged | Affects fixturing |
| Material certificate type | EN 10204 Type 3.1 | Standard for critical components |
Part 5: Quality and Inspection Requirements
| Requirement | Specification | Verification Method |
|---|---|---|
| Bore diameter | H7 | Air gauge or bore gauge |
| Surface finish (bore) | Ra 0.8 μm max | Profilometer |
| Roundness | 0.02 mm | Roundness tester |
| Straightness | 0.05 mm/100 mm | Laser alignment or straightness fixture |
| Concentricity | φ0.10 mm to OD | Dial indicator on centers |
| Borescope inspection | 100% internal visual | Borescope with recording |
| Dimensional CMM | Per drawing | CMM report |
| Material cert | EN 10204 3.1 | Certificate |
| First article inspection | Full dimensions | FAIR per AS9102 or equivalent |
Deep Hole Drilling RFQ Template
Use the following template structure for your RFQ document. Copy and adapt the sections that apply to your specific component.
RFQ COVER PAGE
RFQ NUMBER: [Your RFQ-2026-XXXX]
DATE ISSUED: [YYYY-MM-DD]
RESPONSE DUE: [YYYY-MM-DD]
BUYER: [Company Name]
CONTACT: [Name, Title, Email, Phone]
SHIPPING TERMS: [Incoterm]
PAYMENT TERMS: [Net 30 / Net 60 / etc.]
NDA IN EFFECT: [Yes/No — reference NDA number if applicable]
SUPPLIER: [To be completed by supplier]
QUOTE NUMBER: [Supplier reference]
VALIDITY: [Number of days quote is valid]
LEAD TIME: [First article + production lead time]SECTION A: PART INFORMATION
A1. PART NUMBER: ____________________
A2. PART NAME: ______________________
A3. REVISION: _______________________
A4. ANNUAL QUANTITY: ________________
A5. LOT SIZE: _______________________
A6. DRAWING (PDF): [Attached]
A7. 3D MODEL (STEP): [Attached]SECTION B: DEEP HOLE DRILLING REQUIREMENTS
B1. HOLE DIAMETER: _______ mm Tolerance: _________
B2. HOLE DEPTH: _________ mm
B3. L/D RATIO: _________ :1
B4. THROUGH-HOLE or BLIND: _________
B5. ENTRY SURFACE: Perpendicular / Angled (___°)
B6. EXIT SURFACE: Flat / Angled (___°) / Step
B7. STRAIGHTNESS: _________ mm per _________ mm
B8. SURFACE FINISH (BORE): Ra _________ μm
B9. BORE TOLERANCE GRADE: IT_________
B10. CONCENTRICITY to OD: φ_________ mm
B11. DRILLING DIRECTION: One end / Both ends
B12. STARTING MATERIAL: Solid bar / Tube / Forged blank
B13. PRE-EXISTING BORE: Yes (___ mm) / No
B14. CROSS-HOLES AFTER DRILLING: Yes / No
If yes, quantity: ___ Locations: _________
B15. COOLANT ACCESS: Through-spindle / From workpiece end
B16. ENTRY BUSHING: Required / Not required
B17. SECONDARY OPERATIONS REQUIRED:
[ ] Skiving and roller burnishing (SRB)
[ ] Honing
[ ] Reaming
[ ] Internal grinding
[ ] Deburring (cross-hole intersections)SECTION C: MATERIAL
C1. MATERIAL GRADE: ____________________
C2. MATERIAL CONDITION: ________________
C3. HARDNESS RANGE: ____________________
C4. MATERIAL STANDARD: _________________
C5. STARTING FORM: Bar / Tube / Forging
C6. MATERIAL CERT TYPE: EN 10204 3.1 / 3.2 / NoneSECTION D: QUALITY REQUIREMENTS
D1. ISO 9001 REQUIRED: Yes / No
D2. AS9100 REQUIRED: Yes / No
D3. API Q1/Q2 REQUIRED: Yes / No
D4. FIRST ARTICLE INSPECTION: AS9102 / Internal / None
D5. IN-PROCESS INSPECTION: Frequency _________
D6. BORESCOPE INSPECTION: 100% / Sample (___%) / None
D7. MATERIAL CERTIFICATE: Required / Not required
D8. SURFACE FINISH REPORT: Required / Not required
D9. DIMENSIONAL REPORT: Required / Not required
D10. PRESSURE TEST: ____ bar / Not required
D11. SPECIAL PROCESSES (NDT, etc.): __________________SECTION E: COMMERCIAL
E1. QUANTITY FOR THIS RFQ: _________ pieces
E2. TARGET DELIVERY DATE: _________
E3. PACKAGING REQUIREMENTS: __________________
E4. SPECIAL LABELING: __________________
E5. DOCUMENTATION PACKAGE: __________________Supplier Response Evaluation Criteria
When evaluating quotes from deep hole drilling suppliers, use the following criteria specific to this process:
| Criterion | Weight | What to Evaluate |
|---|---|---|
| Method match | High | Does the supplier's proposed method match the hole requirements? (Gun drilling vs. BTA vs. EDM) |
| Equipment capability | High | Can their machines achieve the required depth, diameter, and straightness? |
| Lead time | Medium | Manufacturing lead time for first article and production |
| Quality certifications | Medium | ISO 9001 minimum; AS9100 or API Q1 for specific industries |
| Past experience | High | Have they drilled similar parts? Request references |
| DFM feedback | Medium | Did they provide design for manufacturability suggestions? |
| Total cost | Medium | Price per piece vs. total cost including tooling, setup, and logistics |
| Inspection capability | High | Can they measure the specified tolerances with calibrated equipment? |
Warning: The cheapest quote for deep hole drilling is rarely the best value. A supplier who does not understand the straightness requirements will quote a low price and produce parts that fail inspection. The lowest responsible quote — not the lowest absolute quote — is the target.
Common RFQ Mistakes and How to Avoid Them
Mistake 1: Omitting Straightness Requirements
Straightness is the most commonly omitted specification in deep hole drilling RFQs. Unlike conventional drilling, deep hole straightness is not guaranteed by the machine and must be specified.
Fix: Always include a straightness callout on the drawing or in the RFQ technical specifications. Even a standard value like "0.05 mm per 100 mm" gives the supplier a target.
Mistake 2: Specifying Unnecessarily Tight Tolerances
A common error is specifying H6 tolerance on a bore that only requires H8 for function. This can double or triple the cost.
Fix: Specify the tightest tolerance only on critical bores. Use general tolerance notes (e.g., ISO 2768-m) for non-critical features. Include a "critical-to-function" note on the drawing highlighting the 3–5 dimensions that truly matter.
Mistake 3: Not Specifying Starting Material Condition
The condition of the starting material (solid bar vs. tube, as-rolled vs. turned OD) directly affects drilling difficulty, tool selection, and cycle time.
Fix: Specify not just the material grade but also the starting form and surface condition. If the part is made from seamless tube, state whether the bore will be machined from the existing tube ID or drilled through solid.
Mistake 4: Missing Cross-Hole Information
If a deep bore will be intersected by cross-holes in a later operation, the deep hole drilling supplier needs to know this — it affects deburring strategy.
Fix: Note on the RFQ whether cross-holes will be drilled after the main bore. Specify whether the supplier is responsible for deburring the intersections.
Mistake 5: No Borescope Inspection Requirement
Without a borescope inspection requirement, the supplier will not budget for internal visual inspection, and the bore quality will go unchecked.
Fix: Specify borescope inspection as a requirement in the quality section of the RFQ. For critical components, state "100% borescope inspection with recorded images."
Mistake 6: Incomplete Drawing Package
Sending a 3D model without a 2D drawing, or a drawing without clear GD&T, forces the supplier to interpret the requirements.
Fix: Always include both a 2D drawing (with GD&T, tolerances, and notes) and a 3D model (STEP format is universal). Verify that the drawing revision matches the model revision.
Summary Table
| Aspect | Key Information |
|---|---|
| RFQ sections | General info, part ID, deep hole specs, material, quality, commercial |
| Deep-hole-specific specs | Straightness, L/D ratio, entry/exit conditions, drilling direction, bushings |
| Material details needed | Grade, condition, hardness, starting form, cert type |
| Quality requirements | ISO 9001, AS9100, API Q1; borescope inspection; FAIR |
| Critical RFQ elements | 2D drawing + 3D model, tolerance grades, surface finish, straightness |
| Most common mistake | Omitting straightness requirements |
| Inspection methods | Air gauge (diameter), profilometer (finish), roundness tester, borescope |
| Supplier selection risk | Lowest quote often misses requirements — evaluate method match first |
| Documentation | Material certs, dimensional reports, borescope images |
| Key principle | Complete RFQs get accurate quotes; incomplete RFQs get risk premiums |
FAQ
What is the most important technical specification to include in a deep hole drilling RFQ?
Straightness is the most commonly overlooked and most critical specification for deep hole drilling. In conventional drilling, straightness is typically adequate without being specified. In deep hole drilling — where L/D ratios exceed 20:1 — the straightness is determined by the drilling method, machine condition, guide bushing setup, and process parameters. Without a straightness specification, the supplier will produce a bore that meets the diameter tolerance but may be curved along its length, causing assembly problems.
Should I send a 3D model or a 2D drawing in my RFQ?
Both. The 3D model (.STEP format is most universal) provides the supplier with the geometry for CAM programming and tool path verification. The 2D drawing communicates the tolerances, GD&T, surface finish requirements, and notes that cannot be conveyed in a model. Neither alone is sufficient. Verify that the model revision matches the drawing revision before sending.
How do I evaluate a deep hole drilling supplier's RFQ response?
Look for four things in the response: (1) the proposed drilling method matches the hole requirements (gun drilling for small diameters, BTA for larger, etc.), (2) the supplier asks intelligent questions about the requirements — this shows they have actually reviewed the RFQ, (3) the quote includes inspection methods that match your requirements, and (4) the supplier provides DFM feedback suggesting improvements. A supplier who provides a simple price without questions or comments has likely not fully evaluated the technical requirements.
A well-structured RFQ is the foundation of a successful deep hole drilling procurement. The template and best practices in this guide are designed to help buyers communicate the specific requirements of deep hole drilling — straightness, surface finish, bore tolerance, entry and exit conditions — that are not captured in standard machining RFQs. The time invested in writing a complete RFQ is repaid in accurate quotes, fewer clarification cycles, and parts that meet specifications on the first delivery.