Quick answer: 7°, 11° and 12° on a tapered rock-drilling system describe the taper geometry at the rod-to-bit connection. They are not interchangeable performance grades. A tapered bit should be matched to a rod made for the same taper angle. The marking H22 identifies the 22 mm hex drill-steel section, but H22 alone does not tell you whether the bit connection is 7°, 11° or 12°. Before ordering, confirm the rod section, taper angle, shank/interface, bit diameter and bit type as one compatible set.
What do 7°, 11° and 12° mean on a tapered drill string?
In hand-held and air-leg top-hammer drilling, the bit is commonly retained on the rod by a tapered socket rather than by a threaded connection. The angle is a connection dimension: it defines the conical mating surfaces between the rod nose and the bit socket.
OEM tooling catalogs treat the taper angle as a specification separate from drill-steel size and bit design. Epiroc's top-hammer catalog, for example, lists distinct H22 connection codes for 7°, 11° and 12° tapers. Sandvik likewise lists tapered-bit families in 7°, 11° and 12° configurations. This is why a buyer cannot safely order only by “H22” or by bit diameter.
| Specification | What it tells you | What it does not tell you |
|---|---|---|
| H22 | Nominal 22 mm hex drill-steel section | Taper angle, bit diameter or bit profile |
| 7° / 11° / 12° | Rod-to-bit taper geometry | Rock condition, bit diameter or cutting-face type |
| H22 × 108 mm | Drill-steel section plus shank/interface length used by the rock drill | Bit taper unless the rod specification also states it |
| 32–40 mm, etc. | Nominal bit or hole-size range | Whether the socket matches the rod taper |
| Button / cross / chisel | Cutting-face design | Connection angle |
Can a 7° bit be used on an 11° or 12° H22 rod?
Treat a different taper angle as incompatible unless the tooling manufacturer explicitly specifies that combination. A 7° bit should be paired with a 7° rod, an 11° bit with an 11° rod, and a 12° bit with a 12° rod.
A mismatched bit may appear to enter the rod nose, but visual fit is not proof of correct contact. Different taper geometries change where the conical surfaces seat. That can create incomplete or localized contact instead of the intended full mating surface. PerfoMax's current 11° H22 chisel-bit and cross-bit pages therefore state that the rod taper must be 11° and that 7°, 11° and 12° tapered components should not be mixed.
| Rod taper | Bit taper | Procurement verdict | Action |
|---|---|---|---|
| 7° | 7° | Potentially compatible | Still confirm H22 section, socket dimensions, insertion depth and bit diameter. |
| 11° | 11° | Potentially compatible | Confirm the exact rod and bit specifications. This is the connection used by PerfoMax's current H22 × 108 mm rod. |
| 12° | 12° | Potentially compatible | Confirm the exact system and dimensions before ordering. |
| 7° | 11° or 12° | Do not mix | Order the bit made for the rod's verified taper. |
| 11° | 7° or 12° | Do not mix | Keep the installed drill string on the same 11° standard. |
| Unknown | Known | Not ready to order | Identify the rod taper from markings, records, drawing or a verified sample. |
“Potentially compatible” means the taper-angle check has passed; it does not replace the rest of the compatibility checks.
Why H22 alone is not enough to order a replacement bit
H22 is useful, but it is only one item in the interface chain. Epiroc's catalog is a useful illustration: the same H22 family appears with several taper-angle codes. A buyer who sends only “H22 bit, 36 mm” can therefore receive a bit with the correct outside diameter but the wrong socket geometry.
For a replacement order, verify at least the following:
- Rock-drill model and shank interface: confirm that the rock drill accepts the rod's shank specification.
- Drill-steel section: H22 in this case.
- Taper angle: 7°, 11° or 12° as actually used by the rod.
- Rod length: selected for hole depth and working clearance.
- Bit diameter: matched to the required hole size and the drill system.
- Bit type: button, cross or chisel according to the installed standard and application.
- Flushing arrangement: confirm that the bit and rod support the required cuttings-removal path.
How to identify an unknown taper angle before ordering
If the existing rod or bit has been in service for a long time, markings may be worn or inventory may have been mixed. Use the following sequence rather than estimating the angle by eye.
- Check the rod marking and original purchase record. Look for the complete rod description, not only H22.
- Check the existing bit marking or packaging. A verified old bit can identify the connection standard if its original specification is known.
- Confirm the rock-drill and rod system. The machine model does not by itself prove the bit taper, but it narrows the installed tooling family.
- Compare with a known matched sample. A clearly identified unused rod or bit from the same fleet is more reliable than a heavily worn component.
- Do not identify 7°, 11° and 12° by visual inspection alone. The differences are too small for a reliable field judgment from appearance.
- Use a drawing, gauge or controlled measurement when records are unavailable. Ask the tooling supplier which dimensions and gauge method are required for that specific product family.
- Send photos and markings with the RFQ. Include side views of the rod nose and bit socket, the full product marking, and a scale reference.
Is 7°, 11° or 12° “better” for drilling performance?
There is no useful universal ranking in which one of these three angles is automatically “better” for hard rock, soft rock or faster penetration. OEM catalogs offer multiple tapered connection systems, and the first selection rule is compatibility with the installed drill steel and bit family.
If you are replacing consumables in an existing fleet, stay with the verified taper standard unless there is a planned system conversion. Changing only the bit angle while keeping the old rods is not a performance upgrade; it creates an interface mismatch.
If you are choosing an entirely new tapered system, evaluate the complete package: rock-drill interface, local bit and rod availability, required hole diameter, rod length, cutting-face design, rock condition and maintenance practice. Then select a matched rod-and-bit system supported by the equipment and tooling supplier. Do not infer a rock-hardness recommendation from the taper angle alone.
How PerfoMax's current H22 tooling fits this compatibility rule
The current PerfoMax H22 × 108 mm tapered drill rod is listed with an 11° bit connection. Its product description also states that the drill bit must use the same 11° taper.
PerfoMax also lists H22 tapered button bits, plus dedicated 11° H22 chisel bits and 11° H22 cross bits. For the current 11° rod, an 11° bit is the correct starting point; exact diameter, profile and availability should still be confirmed for the order.
Six procurement mistakes that create avoidable compatibility problems
1. Ordering by bit diameter only
“36 mm button bit” does not define the socket. Add H22 and the verified taper angle.
2. Assuming every H22 rod uses the same taper
OEM catalogs show H22 systems in more than one taper angle. Treat H22 and taper angle as separate fields.
3. Reusing old bits after changing the rod standard
If a fleet converts from one taper system to another, segregate old inventory. A familiar outside diameter can hide an incompatible socket.
4. Using bit type as a substitute for connection data
Button, cross and chisel describe the cutting face. Each still requires the correct taper connection.
5. Identifying taper angle by eye
Small angle differences are easy to misread, particularly on worn components. Use markings, records, samples or controlled dimensional verification.
6. Sending an RFQ without current-tool photos
For replacement supply, a clear photo of the existing rod marking and bit socket can expose ambiguity before parts are shipped.
RFQ checklist for H22 tapered drill rods and bits
To reduce compatibility back-and-forth, send the following information together:
- Rock-drill make and model
- Current shank specification, for example H22 × 108 mm where applicable
- Verified taper angle: 7°, 11° or 12°
- Rod length and quantity
- Required bit diameter
- Bit type: button, cross or chisel
- Rock type, hardness/abrasiveness information if available, and whether the ground is massive or fractured
- Flushing method
- Photos of current rod markings, rod nose and bit socket
- Whether the request is a like-for-like replacement or a new complete drill-string configuration
If any interface field is unknown, mark it as unknown rather than guessing. A supplier can then ask for the specific measurement or image needed to verify the connection.
Frequently asked questions
Are 7°, 11° and 12° tapered drill bits interchangeable?
No. Treat each taper as a different connection geometry. Match the bit to a rod with the same specified taper angle and then confirm the remaining dimensions.
Is every H22 tapered drill rod 11°?
No. Epiroc's catalog lists H22 examples in 7°, 11° and 12° configurations, and Sandvik's tapered-tool range also includes multiple taper angles. H22 alone does not define the rod-to-bit taper.
How can I identify the taper if the marking is worn off?
Start with purchase records and a known matched sample. If those are unavailable, send the rod and bit photos plus controlled measurements to the supplier and use the manufacturer's drawing or gauge method. Do not rely on visual judgment alone.
Can I temporarily use a 12° bit on an 11° H22 rod?
Do not treat a mismatched angle as a temporary substitute. The correct procurement action is to use an 11° bit on a confirmed 11° rod or replace the rod-and-bit system as a matched set.
Which taper should I buy for the current PerfoMax H22 × 108 mm rod?
The current PerfoMax rod page specifies an 11° bit connection, so a confirmed 11° H22 bit is the correct starting point. The required diameter and cutting-face type must still be selected for the actual hole size, rock condition and drilling system.
Technical references
- Sandvik — Tapered Bits: current tapered-bit family showing 7°, 11° and 12° connection options.
- Sandvik — Top Hammer Drilling Tools 2024 catalog: H22 tapered-tool sections and connection specifications.
- Epiroc — Tophammer catalog: product-code examples for 7° H22, 11° H22 and 12° H22 tapered connections.
Confirm the connection before you buy
For an existing H22 drill string, the lowest-risk route is simple: identify the installed taper, keep the rod and bit on the same taper standard, and confirm diameter and bit type separately. If you are replacing an H22 × 108 mm 11° rod or matching tapered bits, send PerfoMax the rock-drill model, rod marking, taper angle, required bit diameter, photos and quantity through the Request a Quote page. The configuration can then be checked before quotation.