Bit Thread & Make-Up Torque
Bit size to thread connection, then make-up torque for that connection on PDC and roller cone bits — Minimum, Maximum, and Maximum Severe.
| Bit Size (in) | Bit Thread |
|---|---|
| 3 3/4 - 4 1/2 | 2 3/8 REG |
| 4 5/8 - 5 | 2 7/8 REG |
| 5 1/8 - 7 3/8 | 3 1/2 REG |
| 7 1/2 - 9 3/8 | 4 1/2 REG |
| 9 1/2 - 14 3/8 | 6 5/8 REG |
| 14 1/2 - 18 1/2 | 6 5/8 or 7 5/8 REG |
| 18 5/8 - 26 | 7 5/8 or 8 5/8 REG |
| 27 and larger | 8 5/8 REG |
| Pin Size | Minimum | Maximum | Max. Severe |
|---|---|---|---|
| 2 3/8 REG | 3,100 ft-lb | 3,400 ft-lb | 4,000 ft-lb |
| 2 7/8 REG | 5,250 ft-lb | 5,750 ft-lb | 6,800 ft-lb |
| 3 1/2 REG | 7,750 ft-lb | 8,500 ft-lb | 10,000 ft-lb |
| 4 1/2 REG | 18,000 ft-lb | 20,000 ft-lb | 23,500 ft-lb |
| 6 5/8 REG | 43,000 ft-lb | 47,500 ft-lb | 56,000 ft-lb |
| 7 5/8 REG | 72,000 ft-lb | 80,000 ft-lb | 93,000 ft-lb |
| 8 5/8 REG | 101,000 ft-lb | 111,000 ft-lb | 131,000 ft-lb |
| Bit Thread | daN-m | ft-lb |
|---|---|---|
| 2 3/8 REG | 400 - 480 | 3000 - 3500 |
| 2 7/8 REG | 600 - 750 | 4500 - 5500 |
| 3 1/2 REG | 950 - 1200 | 7000 - 9000 |
| 4 1/2 REG | 1600 - 2200 | 12000 - 16000 |
| 6 5/8 REG | 3800 - 4300 | 28000 - 32000 |
| 7 5/8 REG | 4800 - 5400 | 34000 - 40000 |
| 8 5/8 REG | 5400 - 8100 | 40000 - 60000 |
Why the Range Matters
Make-up torque is not a single number to hit — it is a range with a reason behind each end. Below the minimum, the connection is not fully engaged and can work loose under the vibration and cyclic loading of normal drilling. Above the maximum, the pin and box are stressed harder than the connection was designed for, and repeated over-torquing is a direct path to galled threads.
Maximum Severe exists for a specific reason: directional and high-WOB drilling put more working load on a bit connection than a straightforward vertical run, and a connection made up to ordinary maximum can still back off under that extra load. It is not a target to aim for by default — it is the ceiling for when conditions actually call for it.
How This Differs from a Flange Bolt-Up
A bit connection is a tapered threaded joint torqued to a spec — there is no separate gasket, and the seal comes from the metal-to-metal contact of the thread itself once made up correctly. That is a different system entirely from the studded, gasketed flanges used on a BOP stack — see the flange and ring gasket lookup for that side of the rig's connections.
For where the bit sits in the rest of the string and how tool joint connections carry load above it, see the drill string page. Make-up torque only covers how the bit is connected — for the hydraulics happening at the bit face once it's drilling, see the bit hydraulics calculator (total flow area, jet velocity, HHP, HSI).
Bit size alone doesn't say what a bit is built to drill — that's a separate code stamped on the bit itself. See the IADC rock bit and PDC bit classification reference for what those characters mean before the bit ever reaches this torque table.
Frequently Asked Questions
What is make-up torque and why does it matter?
It is the torque applied to fully tighten a threaded connection — here, the bit onto the last drill collar. Too little and the connection can back off downhole, which means losing the bit and fishing for it. Too much and you risk galling the threads or a twist-off. The range in this table exists because "tight" is not a feel, it is a number.
What is the difference between Minimum, Maximum, and Maximum Severe torque?
Minimum is the lowest make-up proven to hold the connection under normal drilling loads. Maximum is the upper limit for ordinary service. Maximum Severe is reserved for conditions that put extra load on the connection — high weight on bit, high torque directional work, or anything expected to work the connection harder than a straightforward vertical run.
How do I find the right thread connection from bit size?
Match the bit diameter to the size range in the first table. Connection size scales with bit diameter — an 8 1/2 in bit runs a 4 1/2 REG connection, for example — because a larger bit needs a physically bigger, stronger connection to carry the same loads without becoming the weak point in the string.
Do PDC and roller cone bits use different make-up torque?
Yes, which is why they are shown separately. The two bit types load the connection differently in service, so a roller cone bit and a PDC bit on the same thread size do not necessarily share the same torque figures — always read from the table matching the bit type in hand.
How is make-up torque actually applied on the floor?
With a calibrated torque sub or tong system that reads the applied torque directly, not by feel or by counting turns. "By feel" make-up is one of the more common causes of galled connections, because the point at which a connection feels tight and the point at which it has reached its correct torque are not the same thing.
Are these torque figures the same across every bit manufacturer?
No — always check the specific bit's own spec sheet first. This table reflects Reed Hycalog's published reference figures as a general guide; actual required torque can vary by manufacturer, thread condition, and the thread compound used.