“How much does deep hole drilling cost?” has two answers — the price of the machine, and the cost of each hole. Both are dominated by a few drivers: method choice, diameter, depth, material, and whether you already own the coolant system. This page walks the actual numbers, from regional machine-hour rates to a fully worked cost-per-hole example.
| Method | Entry machine cost | What you get |
|---|---|---|
| Ejector retrofit | $30k–$100k | Convert an existing lathe; no face seal needed |
| Gundrill machine | $50k–$200k | Single-spindle, small-to-medium bores |
| BTA machine | $200k–$800k+ | High metal removal, larger bores, high volume |
| Multi-spindle / special | $500k+ | High production, large parts (e.g. tube sheets) |
The machine-hour rate — the number your cycle time is multiplied by — varies more by region and machine class than by anything else. These are typical shop rates for precision machining, including labor, depreciation and overhead (material, setup and finishing billed separately):
| Region | 3-axis milling | 4/5-axis & Swiss | Relative cost |
|---|---|---|---|
| United States | $30–$120/hr | $75–$300+/hr | Baseline |
| Europe | €40–€100/hr | €100–€150/hr | Similar to US |
| China | $25–$60/hr | $50–$150/hr | ~30–60% cheaper |
| India | $4–$12/hr | lowest | Lowest-cost option |
What is inside the rate? A typical $80/hr 3-axis rate breaks down roughly as: labor $30 · overhead $24 · depreciation $10 · tooling wear $8 · maintenance $5 · coolant $2 · electricity $1. A deep hole machine adds high-pressure coolant, filtration and chip handling to that base.
Unit cost is machine-hour rate times cycle time, plus tooling and coolant:
| Example bore | Method | Approx. cost/hole |
|---|---|---|
| Ø10 mm × 200 mm, steel | Gundrill | $1–$4 |
| Ø50 mm × 1 m, steel | BTA | $15–$40 |
| Ø8 mm × 300 mm, Inconel | Gundrill | $8–$25 |
| Ø150 mm × 3 m, steel (trepan) | BTA / trepan | $200–$600 |
Vc 80 m/min → spindle ≈ 2,550 rpm; feed 0.03 mm/rev → feed rate ≈ 76 mm/min; 200 mm ≈ 2.6 min cut + ~0.5 min load & retract ≈ 3 min.
3 min at $60/hr = $60/60 × 3 = $3.00.
Carbide gundrill ~$80–$150 spread over many holes per regrind ≈ $0.50–$1.00.
Oil, filtration, inspection ≈ $0.30.
≈ $4 per hole — at $40/hr and a faster 2-min cycle it drops below $2. The same math, scaled up, is why a Ø150 mm × 3 m trepanned bore runs $200–$600.
Tooling is the 10–20% of cost most often mis-priced. Published figures:
| Item | Typical price | Cost driver |
|---|---|---|
| Carbide gundrill (~Ø40 mm) | ~$180 | Reground 8–10× before re-tip |
| Indexable gundrill body | ~$620–$680 | Body only; inserts indexed, no regrind |
| BTA indexable insert | ~$10 each | 3–6 edges per insert |
| Special / form BTA head | $1,000–$5,000+ | Aerospace form tools |
Batch size shifts the cost structure. On a job-shop part, setup and fixed costs dominate short runs and fall off fast as quantity rises (fixed-cost share of per-part price at 10 pcs ≈ 71%, 100 pcs ≈ 28%, 500 pcs ≈ 9%, 2,000 pcs ≈ 3%). For deep holes, the same logic applies to the machine purchase — which is why small-volume users retrofit ejector systems or outsource rather than buy a dedicated machine.
Outsourcing break-even. Decide in-house vs. contract with the classic quantity:
Above the break-even, in-house wins; below it, outsourcing converts fixed cost into variable cost and frees capacity. Example: if a gundrill machine adds $250k of fixed cost and a job runs $5/hole in-house vs. $9/hole outsourced, break-even is 250,000 ÷ 4 = 62,500 holes.
Cost scales faster than diameter — chips, coolant and power all grow. Design for the smallest standard bore that works.
Deeper holes slow feed and add whip/support costs. Beyond ~40:1, most machines need steady rests and dampers.
Superalloys and hardened steels cut speeds 50–80% and multiply tool cost.
Choosing BTA when gundrilling would do (or vice versa) is the single biggest cost error on large bores.