Two DTH bits with the same diameter can have quite different cutting heads. The face may be flat, convex or concave; the carbide buttons may be rounded or more pointed; the gauge row may use a different arrangement. Separate those features before comparing the two tools.
A convex face is not the same thing as a pointed button
Flat, convex and concave describe the profile of the whole bit face. Spherical and ballistic describe individual carbide buttons. A face profile can be paired with different button shapes, so read the face design, gauge buttons and front buttons as separate parts of the specification.
Match the face to the ground
Epiroc's DTH catalogue, page 10, gives the following application guidance for its designs. It provides a useful way to frame a comparison before selecting a complete FSDRILL configuration.
| Design direction | Catalogue application | What to compare |
|---|---|---|
| Flat front | Hard, abrasive formations | Gauge-row configuration and gauge retention |
| Convex front with ballistic buttons | Soft to medium-hard, non-abrasive rock | Drilling progress and button wear |
| Concave front | Medium-hard to hard, less abrasive and fractured formations | Hole-direction control and the complete head configuration |
Add the site's rock condition to its rock name. Two intervals described as limestone may differ in fractures, hard bands and abrasiveness. “Limestone with frequent broken zones” gives the selection discussion a clearer direction than “limestone” alone.
Read the gauge row and front wear separately
Gauge buttons work around the hole perimeter; front buttons break rock at positions across the bottom. Photograph the outer row, the centre and the complete face when considering an alternative.
If wear is concentrated at the gauge, compare the button sizes, arrangement and material options in that region. If front buttons repeatedly chip, record where the damage appears along with changes in the ground and operating conditions. That creates a more useful question than simply asking for more buttons.
Compare the next bit over a full run
Keep the hammer, shank and required hole diameter fixed before comparing head options. To investigate a face-profile change, keep the button specification and other features comparable where possible. If several features change together, treat the trial as a comparison of two complete configurations.
Record more than penetration rate. After a known drilled distance, compare outside-diameter wear, button condition and hole direction. A faster start is useful information, but the condition of the tool later in the run helps show how the choice works over the job.
The FSDRILL catalogue records 146 mm and 152 mm flat-face configurations with two flushing holes. You can compare these configurations on the DTH bit product page. For a replacement, send face, gauge-row and shank photographs on WhatsApp, along with the issue you want to improve: drilling speed, gauge wear or button chipping.