Quick answer: the cheapest rock drilling tool is not necessarily the lowest-cost tool to use. A useful supplier comparison looks at cost per acceptable drilled meter under controlled conditions, not unit price alone. At minimum, buyers should track tool purchase cost, meters drilled before retirement, penetration rate (ROP), tool-change time and abnormal downtime. For a broader operational view, rig, crew, compressor or energy cost, rework and damage to companion components can also be included.
The important point is to define the cost boundary before the trial and use the same boundary, rock conditions, equipment and discard criteria for every supplier. Sandvik's rock-tools services explicitly combine tool-consumption and rig-production data to visualize cost per meter and tool performance, while Epiroc markets rock-tool systems around cost-per-meter and total-cost-of-ownership outcomes. These OEM practices reinforce a simple procurement principle: tool life and drilling productivity need to be evaluated together.
1. What does “cost per meter” mean in rock drilling?
There is no single universal cost-per-meter formula that fits every mine, quarry or contractor. The correct formula depends on what decision you are making. A buyer comparing two button bits may need a narrower tool-cost metric. A drilling manager comparing complete systems may need a fully burdened operating metric.
| Cost layer | Practical formula | Best used for | Main limitation |
|---|---|---|---|
| Single-tool cost per meter | Landed tool cost ÷ acceptable meters drilled before retirement | Quick comparison of bits, rods or another individual consumable | Ignores drilling speed, tool-change time and secondary damage |
| Drill-string consumable cost per meter | Allocated cost of bits + rods + couplings + shank/hammer wear items ÷ acceptable meters | Comparing consumable systems or supplier packages | Still excludes rig, crew and downtime cost |
| Fully burdened drilling cost per meter | Tool cost + rig/crew/air or energy + planned change time + abnormal downtime + rework, divided by acceptable meters | Operational and procurement decisions where productivity matters | Needs reliable cost and production data |
“Acceptable meters” is a deliberate term. If a tool drills 500 m but a portion of those holes must be redrilled because of unacceptable deviation, diameter loss or other quality problems, simply dividing price by 500 m can hide the real cost. Define the hole-quality requirement before the test and use it consistently.
2. Why unit price can point buyers in the wrong direction
Unit price is certain and easy to compare, which makes it attractive in purchasing. But a drilling tool is consumed while enabling an expensive production process. A small difference in tool price can be outweighed by changes in tool life, penetration rate, tool-change frequency or downtime.
| Supplier signal | What unit price shows | What cost per meter adds |
|---|---|---|
| Lower-priced bit | Lower purchase spend per piece | Whether shorter life or slower drilling cancels the saving |
| Higher-priced bit | Higher purchase spend per piece | Whether extra life, ROP stability or fewer changes justify the premium |
| Long-life rod | Higher or lower rod price | How many usable meters are delivered before discard and how often the string is interrupted |
| Fast-drilling tool | Usually invisible | Whether higher ROP reduces rig and crew time per meter without unacceptable wear or hole quality |
| Frequent unexpected failures | May still look cheap | Downtime, companion-component damage and production variability become visible |
Sandvik's +Range materials connect longer tool life with lower cost per drilled meter and reduced handling, and its Track system records tool use, discard reasons and production data. Epiroc likewise describes rock-tool ranges optimized around cost per meter and availability. These are manufacturer-specific product claims, not PerfoMax performance promises, but they show which variables serious rock-tool economics normally examine.
3. The six variables that usually change drilling-tool economics
Tool life
Record total acceptable meters from commissioning to retirement, plus the discard reason. For a fair comparison, suppliers must use the same discard criterion. A bit removed because gauge loss reaches the site's limit cannot be compared with another bit that is kept in service until a more aggressive limit.
Penetration rate (ROP)
ROP affects the amount of rig and crew time required per meter. But ROP should be compared only within similar rock, hole geometry and operating conditions. A faster number from an easier bench is not evidence of a better tool.
Tool-change and handling time
Every bit, rod or coupling change interrupts productive drilling. The effect is small when changes are quick and infrequent, but grows when holes are deep, access is difficult or tool life is short. Record actual change duration instead of assigning an optimistic standard.
Abnormal downtime and failure mode
A planned discard after predictable wear is operationally different from a broken button, cracked body, damaged thread or stuck component. Track unexpected failures separately because they can create recovery work, damage other components or cause lost production.
Hole quality and rework
Cost per meter should not reward meters that fail the site's functional requirement. Depending on the job, that may include diameter, straightness, depth, collar position or blast-pattern tolerance. Use only criteria relevant to the application and measure them consistently.
Operating cost around the tool
For a fully burdened comparison, include the costs that change because the tool changes: rig time, labor, compressed air or fuel/electricity where measurable, service events and rework. Avoid loading unrelated fixed business costs into one supplier trial unless the same accounting method is used for all alternatives.
4. Worked example: how a more expensive bit can still lower cost per meter
The following numbers are hypothetical. They are not PerfoMax field data and are included only to demonstrate the calculation method.
| Variable | Supplier A | Supplier B |
|---|---|---|
| Bit purchase cost | $180 | $260 |
| Acceptable life | 300 m | 450 m |
| Average ROP in controlled test conditions | 35 m/h | 42 m/h |
| Tool-change time | 0.25 h | 0.25 h |
| Illustrative rig + crew cost | $220/h | $220/h |
Supplier A: tool cost = $180 ÷ 300 m = $0.60/m. Drilling-time cost = $220 ÷ 35 m/h = $6.29/m. Change-time cost = (0.25 h × $220) ÷ 300 m = $0.18/m. Simplified total = approximately $7.07/m.
Supplier B: tool cost = $260 ÷ 450 m = $0.58/m. Drilling-time cost = $220 ÷ 42 m/h = $5.24/m. Change-time cost = (0.25 h × $220) ÷ 450 m = $0.12/m. Simplified total = approximately $5.94/m.
This simplified example excludes freight, taxes, compressor/fuel or electricity, maintenance, regrinding and abnormal downtime. Its purpose is only to show why price per piece and cost per meter answer different questions. The result changes immediately if the measured tool life, ROP, hourly cost or trial conditions change.
5. Control the field trial before comparing suppliers
Cost-per-meter data is only useful when the comparison is reasonably controlled. Before the trial, document the variables that can change drilling performance:
- rig and rock-drill or DTH-hammer make/model;
- bit shank, thread and drill-string configuration;
- bit diameter, face design and button configuration;
- rock type, UCS where available, abrasiveness and fracture condition;
- hole diameter, depth, inclination and drilling direction;
- air pressure/flow or hydraulic operating settings relevant to the system;
- feed, rotation and flushing practice;
- operator, shift and site procedure;
- lubrication, regrinding or servicing policy;
- discard/wear-limit criteria and required hole quality.
If geology varies significantly across the site, segment the trial by rock zone instead of blending all meters into one average. Peer-reviewed drilling-cost work and OEM guidance both show that penetration rate, bit wear and drilling economics are condition-dependent; a supplier comparison that changes formation and operating parameters at the same time cannot isolate the tool effect reliably.
6. A seven-step supplier field-trial workflow
- Define the decision. Decide whether you are comparing one component, a drill-string consumable package or the fully burdened drilling cost.
- Establish a baseline. Record the current tool's average meters, ROP, discard reasons, change time and relevant downtime in comparable ground.
- Verify incoming configuration. Confirm thread/shank, dimensions, bit face, buttons, flushing arrangement and other ordered details before the trial starts.
- Assign comparable test holes or zones. Avoid giving one supplier only the easiest or hardest ground. If exact A/B matching is impossible, record geology and segment results.
- Track every tool identity. For each bit/rod/tool, record start and end meter, meters drilled, operating hours where available, regrinds/service events, failure mode, discard reason and abnormal downtime.
- Calculate both tool CPM and operational CPM. Keep the narrow consumable metric separate from the broader rig-time metric so purchasing and operations can see what drives the result.
- Review variability, not only the best result. Compare typical life and ROP, the spread between tools, failure patterns and hole quality. One exceptional tool should not represent a bulk-order decision.
7. What should a buyer conclude from common trial patterns?
| Observed pattern | Possible interpretation | What to verify before buying |
|---|---|---|
| Longer life, similar ROP | Likely lower tool consumption and fewer changes | Same discard criteria, hole quality and ground |
| Longer life, much lower ROP | Tool CPM may improve while rig-time CPM worsens | Calculate fully burdened cost, not life alone |
| Higher ROP, shorter life | May still win if rig-time saving exceeds extra tool consumption | Change time, failure risk and total hourly cost |
| Low average cost but large tool-to-tool variation | Supply or operating consistency may be a risk | Lot traceability, failure reasons and sample size |
| Low unit price with repeated thread/button/body failures | Purchase saving may be offset by downtime or secondary damage | Root cause, compatibility, operating parameters and quality evidence |
| Good meters but more hole rework | Raw life metric may overstate economic value | Acceptable-hole definition and re-drilling cost |
8. Common procurement mistakes
- Ranking suppliers by unit price before running a controlled trial.
- Comparing meters drilled in different geology without segmentation.
- Using the single longest-lived tool as the supplier's expected life.
- Ignoring ROP because “tool life is all that matters.”
- Ignoring change time, recovery time or damage to companion components.
- Using different discard limits between suppliers.
- Counting all meters even when hole quality causes rework.
- Treating an OEM or supplier marketing percentage as a site forecast. Product claims must be validated in the buyer's own application and operating conditions.
9. What to send in an RFQ or supplier trial request
A useful supplier conversation starts with the current operating baseline and the test method, not only a request for the lowest price. Include:
- application: quarry, mine, construction or other drilling work;
- rig, rock drill or DTH hammer model;
- required shank/thread and current drill-string configuration;
- bit/hole diameter and target depth;
- rock type, hardness/UCS if available, abrasiveness and fractures;
- current tool make/model and typical life/ROP if known;
- current discard criteria and major failure modes;
- planned trial quantity and the meters/holes to be evaluated;
- which CPM boundary will be used: tool-only, drill-string or fully burdened;
- required incoming quality documents, dimensional evidence or batch traceability;
- packing and shipping requirements for the trial or bulk order.
PerfoMax currently supplies multiple rock-drilling tool families. Buyers can review the Drill Bits, Drill Rods and DTH Tools collections. For a controlled supplier comparison or quotation, request a quote with your rig, interface, rock and baseline performance data. For the site's current inspection approach, see Quality Control.
Frequently asked questions
How do I calculate drill-bit cost per meter?
For a narrow consumable comparison, divide the landed cost of the bit by the acceptable meters drilled before it reaches the agreed discard criterion. If regrinding or refurbishment is part of normal use, include those costs and the additional meters delivered. For an operational decision, also calculate a broader metric that includes rig time, change time and abnormal downtime.
Should I buy the drill bit with the longest life?
Not automatically. A long-life bit can still be expensive if it drills much more slowly, requires frequent intervention or produces unacceptable holes. Compare life together with ROP, change time, failure mode and hole quality under the same conditions.
How many tools should be included in a supplier trial?
There is no universal sample size because geology, hole length, tool variability and the economic risk of the decision differ by site. Avoid making a bulk-order decision from one exceptional tool. Use enough test units and comparable holes to distinguish a repeatable pattern from normal field variation, and agree the trial design before drilling starts.
Should downtime be included in cost per meter?
Include downtime when the purchasing decision can reasonably change it—for example tool changes, premature failures or recovery work caused by the tool. Keep the downtime category explicit so it is not confused with unrelated site delays.
What is the fairest way to compare two rock-tool suppliers?
Use the same equipment, interface, hole design, rock zone, operating procedure, discard limits and cost boundary; identify every tool; record life, ROP, changes, failures and hole quality; then compare typical performance and variability rather than only the best result.
Technical references
- Sandvik — Centrevo Track: rock-tools consumption, discard reasons, production data and cost-per-meter visualization.
- Sandvik — +Range top hammer drilling rod: service life, handling and cost-per-meter considerations.
- Epiroc — Grey line: rock drilling tools optimized for cost-per-meter operations.
- Energies — Real-Time Drilling Parameter Optimization Model Based on the Constrained Bayesian Method.