Drill Pipe Connections and Sizes
A working reference for the thread forms and sizes on U.S. rigs — and how to tell which one is on your pipe.
Connections are where drill strings are won and lost. Two pipes with identical outside diameter and wall can behave completely differently depending on the thread form cut into the tool joint: coarse API REG threads make up fast and tolerate dirt but carry less torque than a fine NC or IF form, while RC standards like REMET and METZKE are built around a sealed dual-wall assembly rather than raw torque capacity.
This page compares the forms Republic supplies, notes where each is normally used, and lists the sizes currently published in our catalog. If you are unsure what is on your existing pipe, measure the pin outside diameter, count threads per inch and photograph the shoulder — that is usually enough for us to identify the form without a part number.
Send the rig, the hole and the thread you run. We will spec the string and quote it.
Connection forms compared
| Form | Family | Typically used on |
|---|---|---|
| API REG | API | DTH hammers, bit subs and general water well strings |
| API NC | API | Rotary strings where joint torque capacity governs |
| API FH | API | Full-hole rotary applications with larger bores |
| API IF | API | Internal flush rotary strings favouring flow area |
| BECO | Manufacturer | Smaller-diameter DTH pipe, common in water well and geothermal |
| Cubex | Manufacturer | Specific blasthole and production rig fleets |
| Z-thread / RD round | Manufacturer | Legacy and specialty strings still in service |
| REMET | RC standard | Reverse circulation pipe in grade control and exploration |
| METZKE | RC standard | Reverse circulation pipe, widely used on RC fleets |
| DR102 / DR115 | RC standard | Diameter-specific RC assemblies |
Perforator cuts API REG, NC, FH and IF alongside BECO, Cubex, Z-thread and RD round thread on DTH and rotary pipe, and covers the common RC standards on dual-wall pipe. That breadth is why a mixed fleet can consolidate on one pipe supplier without re-threading iron it already owns.
DTH and rotary sizes in stock programme
| Item | Outside diameter | Connection | Details |
|---|---|---|---|
| Perforator DTH/Rotary Drill Pipe — 76.1 mm | 76.1 mm | 2 3/8" API REG, 2"Z, GG2", MAYHEW JR, RD50x1/6", #19 | Specs → |
| Perforator DTH/Rotary Drill Pipe — 88.9 mm | 88.9 mm | 2 3/8" API IF/NC26, 2 3/8" API REG, 2 7/8" API REG, 2 1/2" Z, RD70x1/4", #21, #24 | Specs → |
| Perforator DTH/Rotary Drill Pipe — 101.6 mm | 101.6 mm | 2 7/8 API REG, #24 | Specs → |
| Perforator DTH/Rotary Drill Pipe — 114.3 mm | 114.3 mm | 2 7/8" API IF/NC31, 3 1/2" API IF/NC38, 3 1/2" API FH, 3 1/2" API REG, API NC35, #28, 3" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 127 mm | 127 mm | 3 1/2" API IF/NC38, 3 1/2" API FH, 3 1/2" API REG, 3 1/2" BECO, #28 | Specs → |
| Perforator DTH/Rotary Drill Pipe — 139.7 mm | 139.7 mm | 4 1/2" API REG, 4" API FH/NC40, 3 1/2" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 152.4 mm | 152.4 mm | 4" API IF/NC46, 4 1/2" API FH, 4 1/2" API REG, 4" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 159 mm | 159 mm | 4 1/2" API IF/NC50, 4" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 168.3 mm | 168.3 mm | 4 1/2" API IF/NC50, 5 1/2" API REG, 4" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 177.8 mm | 177.8 mm | 5 1/2" API FH, 5 1/2" API REG, 4 1/2" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 193.7 mm | 193.7 mm | 5 1/2" API IF, 6 5/8" API REG, 5 1/4" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 203 mm | 203 mm | 5 1/2" API IF, 6 5/8" API FH, 6 5/8" API REG, 5 1/4" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 219.1 mm | 219.1 mm | 6 5/8" API REG, 7 5/8" API REG, 6" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 235 mm | 235 mm | 6 5/8" API REG, 7 5/8" API REG, 6" BECO | Specs → |
| Perforator DTH/Rotary Drill Pipe — 254 mm | 254 mm | 8 5/8" API REG | Specs → |
| Perforator DTH/Rotary Drill Pipe — 273 mm | 273 mm | 8 5/8" API REG, 8" BECO | Specs → |
Reverse circulation sizes in stock programme
| Item | Outside diameter | Length | Connection | Details |
|---|---|---|---|---|
| Perforator RC Drill Pipe — 3 1/2" × 3 m REMET | 3 1/2 in | 3 m | 3 1/2" REMET | Specs → |
| Perforator RC Drill Pipe — 3 1/2" × 6 m REMET | 3 1/2 in | 6 m | 3 1/2" REMET | Specs → |
| Perforator RC Drill Pipe — 4" × 3 m REMET | 4 in | 3 m | 4" REMET | Specs → |
| Perforator RC Drill Pipe — 4" × 3 m METZKE | 4 in | 3 m | 4" METZKE | Specs → |
| Perforator RC Drill Pipe — 4" × 3 m DR102 | 4 in | 3 m | DR102 | Specs → |
| Perforator RC Drill Pipe — 4" × 6 m REMET | 4 in | 6 m | 4" REMET | Specs → |
| Perforator RC Drill Pipe — 4" × 6 m METZKE | 4 in | 6 m | 4" METZKE | Specs → |
| Perforator RC Drill Pipe — 4" × 6 m DR102 | 4 in | 6 m | DR102 | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 3 m REMET | 4 1/2 in | 3 m | 4 1/2" REMET | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 3 m METZKE | 4 1/2 in | 3 m | 4 1/2" METZKE | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 3 m DR115 | 4 1/2 in | 3 m | DR115 | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 6 m REMET | 4 1/2 in | 6 m | 4 1/2" REMET | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 6 m METZKE | 4 1/2 in | 6 m | 4 1/2" METZKE | Specs → |
| Perforator RC Drill Pipe — 4 1/2" × 6 m DR115 | 4 1/2 in | 6 m | DR115 | Specs → |
How to identify the connection you run
- Pin OD and box ID
- Measure at the shoulder with a caliper, not a tape.
- Threads per inch
- Count over a measured inch; note whether the form is coarse or fine.
- Taper and shoulder
- Photograph the profile — square shoulder vs. tapered tells us a lot.
- Rig and hammer
- The rig model and hammer make usually narrows it to one or two forms.
How to get pipe quoted
Send the rig make and model, the hole diameter and depth you are drilling, the hammer or bit sub thread you are running, and the rod length your mast and handling system can take. That is enough to price a string. If you are replacing pipe on an existing rig, a photo of the box and pin and a thread gauge reading will confirm the connection faster than a part number from a previous supplier.
Quotes come back with pipe, connection, wall and any subs or crossovers required to make the string work with tooling you already own. Where a size is not on the shelf, the quote states the build and transit lead time rather than an availability promise we cannot hold.
- Rig and hammer
- Make, model, top drive or rotary head thread, and the hammer or bit sub in use.
- Hole program
- Diameter, target depth, angle, and the formation you expect to fight.
- Handling
- Rod length the mast, carousel or rod handler can accept, and single vs. double.
- Existing string
- Connections already in the yard, so crossovers keep the old iron working.
Frequently asked
What is the difference between REMET and METZKE connections?
Open
Both are reverse circulation connection standards used on dual-wall pipe. They are not interchangeable — a string must be consistent, or joined with a crossover sub. Republic supplies pipe in both, plus DR-series diameters.
Can I mix API and manufacturer thread forms in one string?
Open
Only through a crossover sub. Making up two different forms directly will damage both. We quote crossovers with the pipe when a yard runs mixed inventory.
Which API thread should I run?
Open
It depends on the load. API REG is common on hammer and bit sub connections and tolerates field conditions well; NC, FH and IF forms are chosen where joint torque capacity or flow area governs on a rotary string.
How do I identify an unmarked connection?
Open
Measure the pin outside diameter, count threads per inch, photograph the shoulder profile, and send those with the rig and hammer model. That is normally enough to identify the form.
Keep reading
Send the rig. We'll spec the string.
Rig model, hole diameter and depth, hammer or bit sub thread, and the rod length your mast can take. That is enough to price pipe.