Pricing deep hole drilling work is not the same as pricing standard CNC work. The machine hour rate is higher, the tooling cost is significant, and the risk of scrapping a near-complete part affects the price.
Here is how I calculate prices.
Machine Hour Rate
The machine hour rate is the foundation of any quote. I calculate it by dividing the total monthly cost of the machine by the number of billable hours.
| Cost Category | Monthly Cost (Example) |
|---|---|
| Machine payment or lease | $3,000 |
| Coolant (oil, filters, disposal) | $1,200 |
| Tooling (consumables per month) | $800 |
| Electricity | $400 |
| Maintenance (planned) | $500 |
| Floor space | $300 |
| Total monthly cost | $6,200 |
If the machine runs 160 billable hours per month (40 hours/week), the machine hour rate is $6,200 / 160 = $38.75 per hour.
I add operator labor cost on top of the machine rate. At $25/hour operator cost, the total shop rate is approximately $64/hour.
For BTA machines, the machine hour rate is typically 25-35% higher than gun drilling machines due to higher coolant volume, larger tooling, and higher power consumption.
Tooling Cost Per Hole
Tooling is a significant cost in deep hole drilling. I calculate tooling cost per hole separately from machine time.
| Tooling Item | Cost | Life (holes) | Cost Per Hole |
|---|---|---|---|
| Gun drill | $150 | 200 | $0.75 |
| Regrind | $30 | 150 (between regrinds) | $0.20 |
| Guide bushing | $80 | 2000 | $0.04 |
| Total tooling per hole | $0.99 |
For BTA drilling, tooling cost per hole is typically higher because BTA heads and inserts cost more, but the penetration rate is faster so the machine time cost is lower.
I cover detailed tooling cost analysis in Cost Per Hole Deep Hole Drilling.
Cycle Time Estimation
Cycle time drives the machine hour portion of the price. I estimate cycle time based on penetration rate:
| Process | Typical Penetration Rate |
|---|---|
| Gun drilling, 10mm in steel | 15-25 mm/min |
| Gun drilling, 20mm in steel | 30-50 mm/min |
| Gun drilling, 10mm in aluminum | 40-60 mm/min |
| BTA drilling, 30mm in steel | 80-150 mm/min |
| BTA drilling, 50mm in steel | 100-200 mm/min |
I add 20% to the calculated cycle time for setup, loading, and unloading.
For a 200mm deep hole with a 10mm gun drill in steel: 200mm / 20 mm/min = 10 minutes cutting time. With 20% overhead: 12 minutes total. At $64/hour, the machine time cost is $12.80.
Material Factors
Different materials affect pricing significantly:
| Material | Price Multiplier vs Mild Steel |
|---|---|
| Mild steel (1018, 1045) | 1.0x (baseline) |
| Alloy steel (4140) | 1.1-1.3x |
| Stainless steel (304, 316) | 1.5-2.0x |
| Tool steel (D2, H13) | 1.5-2.5x |
| Titanium (6Al-4V) | 2.0-3.0x |
| Inconel 718 | 3.0-5.0x |
| Aluminum | 0.8-1.0x |
The multiplier accounts for slower penetration rates, shorter tool life, and higher risk of scrap.
Minimum Order Quantity
Deep hole drilling has a minimum economic order quantity. The setup time — programming, workholding, tooling selection, first article inspection — takes 1-3 hours regardless of order size.
For small quantities, I calculate the price as:
(Setup time × shop rate + Per-hole time × quantity × shop rate + Tooling cost) × markup
For a single prototype hole, setup cost dominates. For high volumes, setup cost becomes negligible.
I typically charge a minimum of $200-400 for any deep hole drilling job, regardless of how simple it is. Below that minimum, the administrative cost of the order exceeds the profit.
Scrap Risk Premium
Deep hole drilling has a higher scrap risk than standard machining. The part is often 80% complete when the hole is drilled, so a scrapped bore means losing significant upstream value.
I add a scrap risk premium of 5-15% depending on the material and complexity:
| Job Type | Scrap Risk Premium |
|---|---|
| Simple steel, short hole | 5% |
| Steel, deep hole (50:1+) | 8% |
| Stainless or tool steel | 10% |
| Titanium or superalloy | 12-15% |
The premium covers the cost of the occasional scrapped part that cannot be charged to the customer.
Putting It Together: A Sample Quote
For a 20mm diameter, 300mm deep hole in 4140 steel, quantity 50:
| Cost Component | Calculation | Amount |
|---|---|---|
| Setup time | 2 hours × $64 | $128.00 |
| Machine time per hole | 300mm / 40mm/min = 7.5 min + 20% = 9 min | $9.60 |
| Machine time total | 50 × $9.60 | $480.00 |
| Tooling per hole | $0.99 | $49.50 |
| Scrap risk (8%) | ($128 + $480 + $49.50) × 8% | $52.60 |
| Total cost | $710.10 | |
| Price with 20% margin | $887.63 | |
| Price per hole | $17.75 |
Key Takeaways
- Calculate machine hour rate based on total monthly costs divided by billable hours. Include coolant, tooling, and maintenance.
- Separate tooling cost from machine time. Gun drill cost per hole is typically $0.50-2.00 depending on diameter and material.
- Use penetration rate to estimate cycle time. Add 20% overhead for loading and setup.
- Apply material multipliers: stainless costs 1.5-2x steel, superalloys cost 3-5x steel.
- Charge a minimum of $200-400. Deep hole drilling setup cost is significant regardless of order size.
- Add 5-15% scrap risk premium for difficult materials and deep holes.