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Small shops do not need a $200,000 dedicated deep hole drilling machine to produce deep, straight holes. Retrofit systems, gun drilling attachments, and CNC lathe-based setups can deliver production-quality deep holes at a fraction of the cost — provided the shop understands the limitations and requirements of each approach.
Entry Path Options
Cost Comparison
| Approach | Typical Cost Range | Hole Diameter Range | Max Depth | Quality Potential |
|---|---|---|---|---|
| CNC lathe with coolant-through | $5,000–$20,000 (retrofit) | 3–25 mm | 600 mm | Good to excellent |
| Gun drilling attachment | $8,000–$30,000 | 2–20 mm | 500 mm | Excellent |
| Manual lathe conversion | $3,000–$10,000 | 5–30 mm | 300 mm | Fair to good |
| Dedicated entry-level machine | $50,000–$120,000 | 2–40 mm | 1,500 mm | Excellent |
| Used dedicated machine | $15,000–$60,000 | 3–50 mm | 2,000 mm | Excellent (if maintained) |
| Retrofit kit on milling machine | $10,000–$25,000 | 2–15 mm | 400 mm | Good |
Tip: The CNC lathe route offers the best value for most small shops. Many shops already have a lathe capable of deep hole drilling with the right workholding, coolant system, and tooling. The retrofit cost is often 10–20% of a dedicated machine.
CNC Lathe Deep Hole Drilling Setup
Requirements for Lathe-Based Deep Hole Drilling
| Component | Requirement | Notes |
|---|---|---|
| Spindle bore | Minimum 30 mm through-hole | For gun drill shank clearance |
| Coolant-through capability | 40+ bar through-tool coolant | High-pressure coolant unit required if not equipped |
| Sub-spindle or tailstock | Programmable tailstock or sub-spindle | For part support and drill retraction |
| CNC control | Rigid tapping or helical interpolation capable | For controlled feed at entry |
| Workholding | Custom soft jaws or hydraulic chuck | Must not obstruct drill exit |
| Chip management | Adequate coolant flow and chip diversion | Through-spindle coolant preferred |
High-Pressure Coolant Retrofit for Lathes
| Retrofit Option | Cost | Pressure Range | Installation Complexity |
|---|---|---|---|
| External high-pressure pump unit | $3,000–$8,000 | 40–100 bar | Moderate — requires plumbing connection |
| Through-tool coolant adapter | $500–$2,000 | 40–80 bar | Low — mounts in turret or tailstock |
| Rotary coolant union | $1,000–$3,000 | 40–150 bar | High — requires spindle modification |
| Intensifier unit | $4,000–$10,000 | 80–250 bar | Moderate — requires air or hydraulic supply |
Warning: Standard CNC lathes are not designed for high-pressure coolant above 40 bar without a rotary union upgrade. Exceeding the spindle seal pressure rating causes coolant to leak into the spindle bearings, leading to premature bearing failure. Verify the spindle seal rating before installing a high-pressure coolant system.
Gun Drilling Attachments
Attachment Types
| Attachment Type | How It Works | Best For | Limitations |
|---|---|---|---|
| Drill head attachment | Self-contained gun drill head mounts to lathe carriage | Turning centers with live tooling | Limited stroke, single diameter |
| Quill-feed attachment | Independent feed unit with guide bushing | Manual and CNC lathes | Requires setup time for each diameter |
| Sub-spindle mounted | Gun drill mounted in sub-spindle | Swiss-type and multi-spindle lathes | Limited to machine capacity |
| Drill bushing holder with pressure head | Bushing holder with coolant seal | Production runs | Higher cost, more complex setup |
Recommended Attachments by Shop Type
| Shop Type | Recommended Attachment | Budget |
|---|---|---|
| Job shop with CNC lathe | High-pressure coolant unit + turret-mounted gun drill holder | $5,000–$15,000 |
| Production shop | Quill-feed attachment with automatic retraction | $15,000–$30,000 |
| Manual lathe shop | Drill head attachment with coolant-through bushing | $3,000–$8,000 |
| Swiss-type shop | Sub-spindle mounted gun drill holder | $8,000–$20,000 |
Used Dedicated Machines
What to Look For in a Used Deep Hole Drilling Machine
| Check Point | What to Verify | Red Flags |
|---|---|---|
| Spindle condition | Runout at spindle taper and guide bushing | Runout > 0.01 mm |
| Guide bushing holder | Wear on bushing bore, alignment | Oversize bore, visible wear marks |
| Coolant pump | Pressure at full flow, seal condition | Pressure below spec, oil in coolant |
| Coolant filtration | Filter condition, chip handling | Damaged filter media, conveyor issues |
| Way condition | Gib wear, lubrication function | Scoring, excessive clearance |
| Ball screws | Backlash, preload condition | Visible wear, backlash > 0.02 mm |
| Hydraulic system | Pressure, leaks, cylinder seals | External leaks, noisy pump |
| Electrical system | Cable condition, PLC battery, drive faults | Corrosion, outdated control (1990s) |
Used Machine Price Ranges
| Machine Type | Age | Typical Price | Risk Level |
|---|---|---|---|
| Small gun drill (< 15 mm) | 10–20 years | $15,000–$35,000 | Moderate — simpler, easier to repair |
| Medium BTA (20–50 mm) | 10–20 years | $25,000–$60,000 | Moderate to high — coolant system complex |
| Large BTA (> 50 mm) | 10–20 years | $40,000–$100,000 | High — foundation and service costs |
| Gun drill attachment (used) | 5–15 years | $5,000–$15,000 | Low — simple mechanism |
Tip: The coolant pump is the most expensive single repair on a used deep hole drilling machine. A replacement high-pressure piston pump can cost $8,000–$15,000. Test the coolant system under load before buying.
Support Equipment Requirements
Essential Support Equipment
| Equipment | Purpose | Cost Range |
|---|---|---|
| High-pressure coolant pump | Chip evacuation | $3,000–$15,000 |
| Coolant filtration system | Maintain coolant cleanliness | $2,000–$8,000 |
| Guide bushings (set) | Drill entry support | $500–$2,000 |
| Drill sharpening fixture | Maintain tool condition | $1,000–$5,000 |
| Bore gauging | Verify hole size and straightness | $500–$3,000 |
| Workholding fixtures | Custom for deep hole parts | $1,000–$5,000 |
Nice-to-Have Equipment
| Equipment | Purpose | Cost Range |
|---|---|---|
| Coolant chiller | Thermal stability | $3,000–$8,000 |
| Chip conveyor | Automated chip removal | $4,000–$12,000 |
| Mist collector | Air quality | $1,000–$4,000 |
| Tool presetter | Accurate tool setup | $2,000–$6,000 |
Decision Framework
Choosing Your Entry Path
| Your Situation | Recommended Path | Rationale |
|---|---|---|
| Have CNC lathe, need occasional deep holes | CNC lathe + high-pressure coolant + turret holder | Lowest cost, uses existing asset |
| Have CNC lathe, need production deep holes | Gun drilling attachment on lathe | Dedicated function, still uses existing machine |
| No suitable machine, want flexibility | Used small gun drilling machine | Purpose-built, consistent quality |
| No suitable machine, low budget | Manual lathe + drill head attachment | Highest risk, but lowest entry cost |
| Production volume > 1,000 parts/year | Dedicated entry-level machine | Cost justified by volume |
Cost Recovery Calculation
| Annual Volume | Entry Path | Estimated Cost-per-Hole Reduction vs Outsourcing | Payback Period |
|---|---|---|---|
| 100–500 holes | Lathe retrofit | 30–50% savings | 6–18 months |
| 500–2,000 holes | Gun drilling attachment | 50–70% savings | 4–12 months |
| 2,000+ holes | Dedicated machine | 70–90% savings | 12–24 months |
Tip: For small shops, the fastest return on investment comes from outsourcing deep hole drilling first, then bring it in-house once you have the volume to justify the equipment. Buying a dedicated machine before establishing the work usually delays the payback.
FAQ
What is the cheapest way to start deep hole drilling in a small shop?
The cheapest entry path is a manual lathe with a gun drilling drill head attachment and a separate high-pressure coolant pump. Total investment can be under $5,000 for a basic setup. However, this approach is limited in depth (under 300 mm) and requires significant operator skill.
Can I use a standard CNC lathe for deep hole drilling?
Yes, if the lathe has coolant-through tool capability and can accommodate a high-pressure coolant unit. The spindle bore must be large enough for the gun drill shank to pass through. Many small shops successfully run deep hole jobs on standard CNC lathes with a coolant retrofit.
Do I need a dedicated coolant system for small-scale deep hole drilling?
Yes. Standard machine tool coolant pumps (5–15 bar) are insufficient for deep hole drilling. You need a separate high-pressure coolant unit capable of 40+ bar minimum for gun drilling. Even for small diameters, the coolant pump is the most critical piece of support equipment.
How much floor space does an entry-level deep hole drilling setup need?
A lathe-based setup needs no additional floor space — it uses the existing machine. A dedicated small gun drilling machine requires approximately 3 m × 2 m including the coolant tank. Allow additional space for tooling storage and part staging.
Is it better to buy a used dedicated machine or retrofit an existing one?
Retrofit an existing machine if you already own a suitable CNC lathe and have moderate volume (under 2,000 holes per year). Buy a used dedicated machine if you have high volume, need deeper holes (over 600 mm), or require tighter tolerances than a lathe retrofit can deliver.
Small shops have more deep hole drilling options than ever before. Start with a coolant system upgrade on existing equipment and scale up as volume grows. This article reflects industry practice as of 2026.