Repairing a worn drill bit beats buying new when the body is still sound and enough of the cutting structure can be restored for materially less than a new bit — a refurbishment generally runs about 40 to 60 percent of new-bit cost. That case is strongest for a steel-body PDC bit that comes out with worn, chipped, or broken cutters (dull codes WT, CT, BT) over an intact body and near-full gauge: the affected cutters are replaced and the bit goes back in the hole. Replacement wins when the damage is in the body or the gauge — ring-out, through-body erosion, junk damage, a broken body — or, on a roller-cone bit, when the sealed bearing has failed, because those are the parts a repair cannot economically bring back.
The decision is an economic one, not an emotional one: a repair is worth doing when it restores a usable bit for clearly less than the price of a new one, and when the parts that are damaged are the parts a repair can actually rebuild. Across bit-repair shops and bit-maker references, a refurbished fixed-cutter bit typically costs on the order of 40 to 60 percent of a new bit of the same class — roughly half — while returning it close to its original working condition. The savings are real, but they only apply while two things hold true: the body is sound, and enough of the cutting structure survives to be worth rebuilding.
The opposite is also true. Once the damage moves from the cutters into the body or the gauge — or into the bearing on a roller-cone bit — the cost and difficulty of the repair climb quickly, and at some point the honest answer is to replace the bit rather than spend repair money on a tool that will not return to full reliability. The rest of this guide is about telling those two situations apart, and the fastest way to do that is to read the dull grade the bit came out with.
A repair is a set of separate operations, not one process. Which ones a given bit needs depends on how it wore, and which ones are even possible depends on the body type (covered in the next section). These are the operations a repair shop draws on.
| Repair operation | What it does | Where it applies |
|---|---|---|
| Cutter replacement / re-tipping | Worn, chipped, lost, or braze-released PDC cutters are removed and new cutters are brazed into the pockets, returning the cutting structure to a sharp, full-height condition. | Steel and matrix bodies — cutters are brazed in on both. |
| Gauge and OD restoration | The gauge row and outer diameter are rebuilt so the bit again cuts a full-diameter hole and holds it, correcting an undergauge or rounded-gauge condition. | Practical on steel; limited on matrix. |
| Nozzle and hydraulic reconditioning | Eroded or plugged nozzles are replaced and the flow passages cleaned, so cleaning and cooling flow returns to the design the bit was built for. | Steel and matrix bodies. |
| Blade and body weld repair | Eroded or cracked blade and body steel is built back up by welding and hardfacing, then re-machined to profile. | Steel bodies only. |
| Cutter-pocket re-machining | A damaged pocket is re-cut into the steel so a new cutter seats and brazes correctly, rather than the bit being scrapped for a few bad pockets. | Steel bodies only. |
Body type is the single most important thing that decides how far a bit can be repaired, so it is worth stating plainly. A PDC bit is built on one of two bodies: a machined steel body, or a cast matrix body — a tungsten-carbide composite. Both hold their cutters the same way: each cutter is brazed into a pocket, so on both bodies an individual worn or lost cutter can be replaced. The difference is what happens when the damage reaches the body itself.
Steel is weldable and machinable. Eroded or cracked steel can be built back up by welding and hardfacing and then re-cut, and damaged cutter pockets can be re-machined — which is why steel-body bits are the more repairable of the two and can go through multiple repair cycles. A cast tungsten-carbide matrix is not weldable in the same way; it resists erosion far better in hard, abrasive, hot holes, but once the composite body itself is significantly damaged it generally cannot be rebuilt, and the bit is replaced. The nuance that matters: matrix is not "unrepairable" — its brazed cutters are still replaceable — but its body damage usually is not.
| Steel body | Matrix body | |
|---|---|---|
| Replace individual cutters | Yes — cutters brazed into machined pockets, readily swapped. | Yes — cutters are brazed into the cast matrix and can be replaced individually. |
| Repair body damage | Yes — weldable and re-machinable; eroded or cracked steel can be built back and re-cut. | Generally no — a cast composite that is not weldable the same way; major body damage usually means replacement. |
| Rebuild gauge / OD | Practical, by welding and re-machining the gauge. | Limited — cast matrix material is hard to restore. |
| Typical outcome | Multiple repair cycles; longer working life per bit. | Cutter-level repair yes; body damage usually ends the bit. |
| The trade-off | Softer body, more prone to erosion in abrasive rock — but easier to bring back. | Erosion-resistant in abrasive and hot holes — but harder to repair once the body is hurt. |
This is why the same dull grade can point to a repair on one bit and a replacement on another: an erosion mark at the shoulder that a steel body can be welded and re-cut through may be the end of a matrix bit.
The IADC dull grade already carries the decision. It records how worn the cutting structure is, what kind of damage it shows and where, the gauge condition, and — on a roller-cone bit — the bearing. Those are exactly the inputs the repair-or-replace decision needs. The table below maps the common dull-grade signals to a general read; treat it as a starting point, not a verdict, because body type and the number of sound cutters left decide the borderline cases. Every two-letter code below is decoded on the companion IADC dull grading page.
| Dull-grade signal | What the bit is telling you | General read |
|---|---|---|
| Low inner and outer wear (roughly 0–2 of 8), in gauge (I), pulled at total depth (TD) | The cutting structure is barely used and the hole is still full diameter. | Generally re-run as-is — no repair needed. The bit was well matched to the section. |
| Moderate cutter wear or damage — WT, CT, BT — over a sound body and near gauge | Cutters worn, chipped, or broken, but the body and gauge are intact. | Repair is usually economical, especially on a steel body: replace the affected cutters and re-run. |
| Lost cutters (LT) or bond failure (BF) on an otherwise sound body | Cutters are gone or a braze has released, but the body is still good. | Generally repairable — re-braze or replace the cutters, provided enough pockets are sound. |
| Rounded gauge (RG) or ring-out (RO) | The gauge is worn to a rounded profile, or a concentrated ring of cutting structure is gone. | Steel body: gauge is often restorable, so weigh a repair. A severe ring-out across the profile generally points to replacement. |
| Through-body erosion or washout (ER, WO), junk damage (JD), or a broken body | The fluid has cut into the body, or impact or metal debris has damaged the body itself. | Steel: sometimes weld-repairable. Matrix: generally replace — the composite body is not weldable. |
| Roller-cone seal or bearing failure — a position-5 grade of F, or a dragged cone (CD) | The seals have failed and the sealed bearing is compromised. | Generally the end of a sealed roller-cone bit's reliable life — replace. |
Two worked grades show how the read comes together. A fixed-cutter bit graded 2-3-WT-S-X-I-CT-PR came out with moderate, even cutter wear heaviest on the shoulder, chipped cutters as the secondary, still in gauge, pulled on penetration rate. The damage is all in the cutting structure and the body and gauge are sound — a straightforward repair candidate, most clearly so on a steel body: replace the shoulder cutters and re-run. Contrast a bit graded 4-6-ER-A-X-3-RO-PR: heavier wear, erosion across all areas as the main characteristic, 3/16 inch undergauge, ring-out as the secondary. Here the damage has reached the body and the gauge at once. On a steel body that is a hard repair the shop may still take on; on a matrix body the un-weldable erosion usually settles it toward replacement.
The reason-pulled code (position 8) keeps the decision honest. A lightly worn bit pulled for a downhole motor failure (DMF) or a formation change (FM) says nothing about the bit and needs no repair at all — it just needs to go back in. Read the whole grade, not one alarming code: it is the combination of cutting-structure wear, body and gauge condition, bearing state, and reason pulled that tells you whether to repair, replace, or simply re-run.
A sound steel-body bit is not a one-run tool. It can generally be rebuilt and re-run several times, and vendors report high-cycle cases well beyond that — but a fixed number is misleading, because each rebuild depends entirely on how much sound structure survives the run. The governing test is how many of the original cutters are still reusable: a common guideline is that a steel-body PDC bit stays worth repairing only while a meaningful share of its cutters — roughly a quarter or more — remain sound. Below that, a repair is rebuilding most of the bit, and buying new starts to make more sense. Matrix bits follow the same cutter logic but exit sooner, because body damage that a steel bit could be welded through generally retires a matrix bit.
Repair-or-replace is a read Ironstone gives before any order is on the table, and it costs you nothing but a photo. Send us the bit type and size, whether the body is steel or matrix, and the dull grades from the last run — or clear photographs of the cutting structure and gauge — and we read them the same way this guide does: we tell you whether the bit is a repair candidate or a replacement, and the reason. Because that read asks only for a worn bit and a picture, it is a lower-commitment way to test our judgment than ordering a new bit — which is exactly why we lead with it. Send your bit's dull grades or photos on WhatsApp for an honest repair-or-replace read.