Gauge wear on an H22 tapered drill bit is the loss of diameter or roundness at the outside cutting edge. Check it by cleaning the bit, measuring across the widest outer cutting points in several orientations, comparing the results with the bit's documented new diameter, and inspecting the carbide and steel body at the same time. A worn bit should not be kept in service simply because it still drills: an undersize or uneven gauge can change hole clearance, increase rubbing, worsen flushing and make a later full-size replacement bit difficult to run into the hole.
There is no universal millimetre limit that applies to every H22 bit design, rock condition and hole requirement. Use the bit supplier's limit, the hole specification and a site-approved inspection rule. If those are unavailable, record the actual measurements and operating symptoms and obtain a model-specific decision before regrinding or continued use.
What gauge wear changes in an H22 drilling system
The gauge is the outermost part of the bit face that establishes the hole diameter. On a button bit, the gauge row and adjacent steel carry this job; on cross and chisel profiles, the outer cutting edges define the gauge. The H22 designation describes the drill-steel cross-section, not the bit's cutting diameter, so maintenance records must keep those two dimensions separate.
As the outside cutting points wear, the drilled hole can become smaller than the nominal bit size. If the wear is uneven, the bit may also drill an irregular hole or rub one side more heavily. Gauge retention depends on carbide condition, button profile, rock abrasivity, rotation, feed, flushing and any approved regrinding practice. The exact service limit must still come from the relevant bit design and hole requirement.
For the general distinction between outside gauge cutters and central face cutters, use the gauge buttons vs face buttons guide. This page owns the H22 field-measurement, under-gauge-hole and replacement decision.
| Observed condition | Likely meaning | Required check |
|---|---|---|
| Similar readings in all directions, but below the new-bit record | Generally uniform gauge loss | Compare with the approved diameter limit and hole requirement |
| Readings differ by orientation | Out-of-round or localized gauge wear | Check alignment, feed, rotation, collaring and rock discontinuities |
| Diameter loss plus polished steel around the skirt | Body rubbing or inadequate clearance | Inspect flushing, cuttings removal and hole condition |
| Flat, chipped or cracked carbide | Cutting structure damage, not just diameter loss | Quarantine for a competent regrind or replacement decision |
| Loose carbide, severe steel wash or a body crack | Structural damage | Remove from service; do not return it to drilling |
A repeatable gauge-wear inspection procedure
1. Identify the exact bit before measuring
Record the bit profile, nominal diameter, taper angle, supplier or drawing reference, and whether the bit has previously been reground. Do not treat all bits on an H22 rod as interchangeable. A nominal diameter without the connection and face design is incomplete identification; see the H22 tapered button-bit size guide for the selection boundary.
2. Clean the measuring surfaces
Remove compacted cuttings, oil film and loose corrosion from the outside cutting points and skirt. Measure only after the bit is cool enough to handle and dimensionally stable. Dirt between the caliper jaws and carbide can create a false high reading; a raised burr can do the same. Do not grind away evidence merely to make the measurement easier.
3. Establish the reference diameter
The best reference is a controlled record of the same bit when new, supported by the supplier drawing or purchase specification. A catalogue nominal can be useful, but it should not replace the agreed product tolerance. If no baseline exists, compare the used bit with an unused bit of the same controlled part number and lot only as a screening check, then ask the supplier to confirm the acceptance rule.
4. Measure across the true outer gauge
Place the caliper square to the bit axis and contact the opposite outermost cutting points. Do not measure across two convenient features that sit inside the real gauge. Take readings at several rotational positions, record every result and note the smallest and largest values. The spread between readings matters because an apparently acceptable maximum can conceal a badly worn sector.
5. Inspect the face, carbide and body
Diameter alone cannot release a bit for service. Look for carbide flats, chips, cracks, looseness, missing inserts, steel wash around the buttons, skirt polishing, flushing-hole blockage and cracks in the steel body. Photograph the face and side profile with the bit ID visible. If a defect changes the structural condition, a favourable diameter reading does not override it.
6. Link the measurement to the hole result
Compare the bit record with hole diameter, penetration trend, flushing behaviour, rotation smoothness and any difficulty withdrawing the drill steel. A shrinking hole can have more than one cause, including rock closure, deviation or cuttings accumulation. Gauge measurements help separate bit wear from those other conditions; they do not prove the cause by themselves.
How to diagnose uneven gauge wear
Uniform abrasive wear usually produces broadly similar diameter readings. A pronounced difference by orientation points to a loading or contact problem that deserves investigation before another bit is installed. Common contributors include poor collaring, side loading from an angled operator position, bent drill steel, insufficient rotation, excessive feed, fractured ground and ineffective flushing.
| Pattern | Check first | Why it matters |
|---|---|---|
| One sector worn more than the opposite side | Rod straightness, drill alignment and feed direction | Side loading can keep one gauge sector in heavier contact |
| Gauge carbide worn while face buttons remain relatively sharp | Rock abrasivity, rotation and wall contact | The hole wall may be consuming the outer row faster than the face |
| Steel eroded around otherwise intact carbide | Flushing path, blocked holes and recirculating cuttings | High-velocity abrasive cuttings can wash the supporting steel |
| Repeated chipping after regrinding | Grinding profile, carbide temperature and residual cracks | An incorrect grind can leave stress raisers or damaged carbide |
| New bits repeat the same one-sided pattern | Drill, rod, operator setup and ground condition | The root cause may sit outside the consumable |
If penetration has slowed but gauge readings remain stable, use the wider diagnostic sequence in H22 tapered drilling is slow. That guide separates air supply, flushing, bit condition, feed and rock changes rather than blaming diameter alone.
Regrind, continue, quarantine or replace?
Continue in service only when the diameter and roundness meet the approved limit, the carbide and steel body are sound, flushing holes are open and drilling behaviour remains normal. Record the inspection interval so a trend can be seen before the bit reaches a critical condition.
Send for competent regrinding when the bit design is intended to be reground, adequate carbide remains, and no crack, looseness or body damage disqualifies it. Controlled regrinding can restore the intended cutting profile when the design and remaining carbide allow it, but it cannot restore lost gauge diameter or repair a damaged taper. Confirm that the grinder, cup profile and operator procedure match the actual carbide shape.
Quarantine for technical review when readings conflict, the baseline is missing, the bit is out of round, or the hole result is outside specification. Mark the bit so it cannot re-enter the rack by mistake. Keep the measurement sheet, photos, drilled metres or holes if recorded, rock description, air and flushing observations, and the related rod and machine identity.
Replace and investigate when the bit exceeds the approved wear limit, produces unacceptable hole size, has loose or missing carbide, shows cracking, or has severe steel wash. Installing a new full-gauge bit without investigating the old bit's wear pattern can repeat the damage or cause the replacement to bind in an under-gauge hole.
Controls that make bit-wear records useful
- Assign a simple bit ID and retain the nominal diameter, taper angle and profile with it.
- Use one measuring method, the same reference features and a checked instrument.
- Record minimum and maximum gauge readings, not only a single average.
- Separate normal wear from damage such as cracks, loose carbide or blocked flushing holes.
- Track the rod and drill used when repeated one-sided wear appears.
- Do not mix a worn bit and a new bit in the same hole without checking clearance and the site procedure.
- Set the inspection trigger from operating experience and supplier guidance rather than waiting for obvious failure.
Information to send when requesting replacement H22 bits
A useful RFQ should identify more than “H22 bit.” Send the rod cross-section and shank arrangement, taper angle, required nominal bit diameter, bit profile, face and carbide configuration, flushing arrangement, rock description, hole application and current wear evidence. Include the minimum and maximum readings from representative used bits and explain whether the problem is undersize holes, short life, uneven wear or slow penetration.
PerfoMax's active H22 taper button-bit range covers nominal inquiry sizes from 30 to 40 mm, but diameter alone does not confirm compatibility. The final quotation should control the taper, face design, carbide arrangement and drilling conditions as one specification.
Frequently asked questions
Where should I measure an H22 button bit?
Measure across the opposite outermost gauge cutting points, with the caliper square to the bit axis. Repeat at several orientations and retain the smallest and largest readings. Avoid measuring on dirt, a burr or an inner face button.
Does a smaller measured diameter always mean the bit must be discarded?
No. The decision depends on the approved wear limit, hole requirement, bit design and the condition of the carbide and body. A model-specific regrind may be possible, but regrinding cannot restore diameter already lost from the gauge.
Why can a new bit stick after a worn bit drilled the hole?
The worn bit may have produced an under-gauge or irregular hole. A new full-gauge bit then has less clearance, especially if cuttings remain or the hole has deviated. Check the old-bit diameter and the hole before forcing the replacement.
Can I judge gauge wear only by penetration rate?
No. Penetration also changes with air pressure, feed, rotation, flushing, rock and operator technique. Direct measurement and visual inspection are needed to distinguish gauge loss from other causes.
Is one caliper reading enough?
No. One reading can miss local wear or out-of-roundness. Take several orientations, record the range and investigate a large spread before returning the bit to service.
Request a controlled H22 bit match
Send the current bit diameter and profile, taper angle, rod and rock-drill model, hole requirement, rock condition, flushing method and photos of the wear pattern. PerfoMax can review the information against the current H22 tapered-bit supply scope and prepare a project-based specification for quotation.