Gauge Buttons vs Face Buttons on Rock Drill Bits: What They Do and Why Gauge Wear Matters

Direct answer: Face buttons and gauge buttons are both carbide inserts on a button bit, but they do different jobs. Face buttons are concentrated toward the center of the bit and mainly break rock at the bottom of the hole. Gauge buttons sit around the perimeter and also create the side clearance that lets the bit rotate freely while helping the drilling system maintain the intended hole gauge. That is why a bit can still have usable-looking face buttons yet become inefficient or risky to run if the gauge row has worn excessively.

This distinction matters on both top-hammer and DTH button bits. The exact number, angle, size, shape and carbide grade of the buttons vary by bit design, but the buyer and driller should always evaluate the center/face zone and the outer gauge zone separately.

1. Gauge Buttons vs Face Buttons: Quick Definition

Sandvik’s current resharpening guide makes the functional distinction explicit: the center face buttons strike downward, while the perimeter gauge buttons also provide side clearance so the bit can rotate and cuttings can evacuate. This is a useful way to understand why the two button zones should not be treated as interchangeable.

2. What Does “Gauge” Mean on a Rock Drill Bit?

In drilling language, gauge refers to the effective outside diameter of the cutting structure. On a button bit, the outer gauge buttons and surrounding bit-body geometry help establish the clearance between the rotating bit and the wall of the hole.

This is different from simply checking the height of one carbide insert. A useful gauge inspection looks at the full bit diameter across the outer cutting structure, the profile of the perimeter buttons, and whether the bit head still tapers away correctly behind the cutting edge.

For procurement, nominal bit diameter is the starting specification. For used-tool control, the site or OEM should define how diameter is measured, what gauge or template is used, and the minimum acceptable diameter before the bit is removed from service.

3. Why Gauge Wear Matters Even When the Face Buttons Still Look Usable

Loss of side clearance

Gauge buttons work at the outer edge of the hole. As their profile and the surrounding steel wear, the original relationship between the cutting edge and the bit body can change. Sandvik describes severe gauge wear as anti-taper: the bit no longer has the intended backward taper behind the face. In that condition, the hole can provide too little clearance around the body, increasing the risk of the bit jamming and increasing load on the rotation motor.

Loss of effective hole gauge

A nominal 38 mm, 76 mm or 115 mm bit is not useful simply because that diameter was printed on the original specification. The used bit must continue to cut an acceptable diameter for the hole requirement. Epiroc’s current top-hammer bit guidance explicitly treats diameter wear as a design and service-life variable, alongside penetration rate and hole straightness.

Changes in drilling behavior

Excessive button wear does more than consume carbide. Flattened profiles reduce the ability of the buttons to concentrate impact into the rock. Sandvik notes that over-worn buttons can reduce drilling speed and straightness and increase the risk of damage to the bit, drill string and rig. Gauge wear adds the extra problem of deteriorating perimeter clearance.

Higher cost per meter

A bit that still “has carbide left” is not automatically economical to keep drilling. If penetration falls, rotation load rises, hole diameter becomes unacceptable, or the bit requires additional reaming or recovery work, the apparent saving from delaying maintenance can be outweighed by machine time and downstream tool wear.

4. Face Wear vs Gauge Wear: What the Symptoms Suggest

These are diagnostic clues, not stand-alone failure conclusions. Rock abrasiveness, rotation, feed, percussion, flushing, hole condition and incorrect bit selection can all change wear patterns.

5. How to Inspect Gauge and Face Buttons in the Field

1. Clean the bit first. Remove packed fines and surface contamination so the carbide, steel body and flushing features are visible.
2. Identify the original specification. Record bit type, connection, nominal diameter, face design and button profile. Do not evaluate a used bit against a generic photo.
3. Inspect face buttons separately. Look for wear flats, loss of the original profile, cracks, chips, broken carbide and abnormal protrusion.
4. Inspect the full gauge row. Check all perimeter buttons for uneven wear, anti-taper, damage and differences around the circumference.
5. Measure the complete bit diameter. Use the correct manufacturer/site template or gauge. Sandvik recommends checking the full diameter regularly rather than judging gauge condition visually.
6. Inspect the steel body and flushing features. Look for excessive body wear, deformed areas, damaged flushing holes or grooves, and insufficient clearance behind the gauge row.
7. Compare with drilling data. Record meters drilled, rock condition, penetration trend, rotation behavior and any increase in torque or sticking.
8. Decide regrind, repair or replacement under an approved procedure. The tool manufacturer’s limits and the site’s hole-diameter requirement should control the decision.

6. When Should a Button Bit Be Reground?

There is no safe universal meter interval because wear rate changes with rock, drilling parameters, carbide, button profile, bit diameter and flushing. A condition-based interval is more useful.

As an OEM example, Sandvik recommends resharpening before the wear flat on any button reaches 50% of that button’s diameter and at the first sign of anti-taper on the gauge buttons. Its guide also recommends responding to unexplained penetration loss and carbide surface cracking. Epiroc’s grinding guidance similarly describes establishing a grinding interval around the stage where the wear flat reaches roughly 40–50% of button diameter.

These percentages are manufacturer maintenance guidance, not universal acceptance tolerances for every PerfoMax or third-party bit. For a specific product, use the applicable drawing, service procedure and grinding-cup/profile instructions.

7. When Does Gauge Wear Mean the Bit Should Be Replaced?

Replacement should be driven by serviceability, not by a single generic number. Common triggers include:

• the full bit diameter falls below the agreed minimum for the hole requirement;
• gauge damage cannot be restored within the manufacturer’s permitted grinding procedure;
• buttons are broken, missing or damaged beyond the applicable service rule;
• the bit body no longer safely supports the carbide or maintains the required profile;
• cracks or other structural damage make further drilling unsafe;
• the bit repeatedly creates unacceptable hole diameter, sticking or rotation load after operating causes have been checked.

Sandvik’s current guide recommends using the correct diameter template and discarding a bit when its full diameter has become too small for that template. Epiroc likewise emphasizes maintaining diameter and avoiding excessive grinding of the perimeter.

8. Do Gauge and Face Buttons Always Use the Same Shape?

No. Button layout is a bit-design decision. Sandvik describes spherical buttons as a robust profile for hard and abrasive rock and ballistic buttons as a slimmer profile that can favor penetration in softer to medium-hard formations. OEM designs may use different profiles or carbide grades in different positions.

Do not convert that directional guidance into a rule such as “all gauge buttons must be spherical” or “all face buttons should be ballistic.” The correct combination depends on the bit family, diameter, rock, hammer/rock-drill system and the manufacturer’s design.

For example, PerfoMax currently supplies H22 tapered button bits in 30–40 mm sizes, where bit face and button configuration are selected for the application. PerfoMax’s DTH drill bit selection page likewise treats shank, diameter, face, button pattern and flushing as configuration variables rather than one fixed universal bit.

9. What Buyers Should Specify in an RFQ

If gauge retention or button wear is important to your operation, send more than a nominal diameter.

• drilling system: tapered top hammer, threaded top hammer or DTH;
• exact rod thread, taper or DTH hammer shank;
• nominal bit diameter and required finished-hole diameter;
• current bit face design and button layout, with photos if replacing an existing tool;
• rock strength, abrasiveness, quartz content if known, and fracture condition;
• typical hole depth and drilling direction;
• air or water flushing arrangement;
• current wear problem: face flattening, rapid gauge loss, button breakage, body wash, sticking or deviation;
• site method for checking used-bit diameter and any minimum acceptance requirement;
• quantity, destination, packaging and inspection-document requirements.

Browse PerfoMax’s current Drill Bits collection or send the drilling system, current bit and rock information for an RFQ review.

10. Common Gauge-Button Mistakes

• Looking only at the center buttons. A usable face does not prove the bit is still in gauge.
• Measuring one carbide insert instead of the full bit diameter. Gauge is a whole-head geometry question.
• Using a fixed meter interval for every rock. Abrasiveness and operating parameters can change the correct grinding interval dramatically.
• Grinding away the perimeter aggressively. Removing too much carbide or steel can reduce effective diameter and shorten service life.
• Assuming a larger wear flat is only a bit-cost issue. Overdrilling can also affect penetration, straightness, rotation load and the wider drill string.
• Ordering only by diameter. Connection, shank/taper, face, button pattern and flushing still have to match the drilling system.

FAQ

Are gauge buttons the same as face buttons?

No. Face buttons are mainly positioned in the center/inner face and break rock at the bottom. Gauge buttons are on the perimeter and also create the side clearance needed around the rotating bit.

Do gauge buttons control hole diameter?

They are a major part of the outer cutting structure that maintains effective bit gauge. The complete bit-body and button geometry determines the cutting diameter, so inspect the full bit rather than one button alone.

Can I keep drilling if the face buttons look good but the gauge buttons are worn?

Not automatically. Excessive gauge wear or anti-taper can reduce clearance, raise rotation load and increase jamming risk. Measure the full bit diameter and follow the manufacturer/site service limit.

How should gauge wear be measured?

Use the correct full-diameter template or gauge for the bit size and inspect the perimeter profile for anti-taper and uneven wear. Keep a new or approved reference where possible.

When should a button bit be reground?

Use the applicable OEM procedure and a condition-based interval. Sandvik currently recommends grinding before any button wear flat reaches 50% of button diameter and at the first sign of gauge anti-taper; other manufacturers may define their own intervals.

Related PerfoMax Guides

• Button Bit Regrinding Guide: When to Sharpen Carbide Buttons and When to Replace
• Carbide Button Failure Guide: Why Drill Bit Buttons Break, Crack, or Pop Out
• Rock Hardness vs Abrasivity in Drilling
• H22 Tapered Button Bit Size Guide: How to Choose 30–40 mm Diameter

Technical Source Notes

• Sandvik — Expert Guide to Effective Resharpening of Drill Bits: face/gauge button functions, wear-flat, anti-taper, diameter templates and resharpening practice.
• Epiroc — Grinding Equipment Product Catalog: bit grinding intervals, gauge anti-taper and perimeter-clearance guidance.
• Epiroc — Underground Drill Bits: diameter wear, penetration-rate and hole-straightness design considerations.