trepanningConfluent Maine’s deep hole drilling expertise dates back more than sixty five years. In that time we have expanded our portfolio of capabilities to include other precision boring and machining processes.

While gun drilling efficiently produces deep, concentric bores in barstock, gun drilled holes are typically less than 1.5 inches in diameter. For larger diameter holes, we typically rely on trepanning to efficiently remove large amounts of material.

Like gun drilling, trepanning efficiently produces deep bores. With subsequent processing, THI can produce excellent concentricity in larger tubing sizes. Unlike gun drilling, trepanning leaves the core of the bar intact. Trepanning and gun drilling both use a high pressure coolant and lubricant to machine holes with excellent ID finishes and tight tolerances. But in gun drilling, the core of the bar is reduced to chips, which are then evacuated from the drill through a “V” shaped flute in the bit. Trepanning does not break down the center, solid core of the tube into chips, but rather leaves it intact for testing, reclamation or repurposing.


“The machine can make a perfect part, but it needs help. It’s up to us to throw in the human input that makes the difference.”

Having a solid core to work with post manufacturing gives trepanning an edge when a project requires expensive metals or alloys such as titanium. This may represent a considerable downstream cost savings for customers.

The intact core left by trepanning is also easy to handle. If your company’s design or product requires post processing testing, the core can be easily shipped to a laboratory for further testing. Engineers and design professionals in the nuclear power generation industry often rely on trepanned materials because they are easily indexed and tested for critical safety components and systems in their power plants.

Confluent Maine typically uses trepanning to remove material in a cost effective manner. Our trepanning capabilities range from 1.250” to 3” IDs. We combine trepanning with additional machining processes such as honing to produce extremely precise Internal Diameter dimensions with surface finishes of Ra 32 and finer.

Trepanning ID/OD

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