Brazed Joint

T-DRILL Collaring Method

Tee Forming – The T-DRILL method was developed in the 1970’s. The idea that pipes and tubes could be branched much more quickly and cost-effectively into end products of greater strength and higher quality was as revolutionary as it was simple, and one of the major inventions in the field.

As the tee is fabricated from the basic tube, no costly T-pieces are needed. Instead of three joints there is only one joint! This saves a lot of time and means considerably lower total costs. The construction also makes the tube stronger and provides for better flow characteristics.

Tee Forming – Pipe Branching – Collaring

Pipe branching – i.e. connecting a branch pipe to a run pipe – using T-DRILL method is also called collaring. The joint can be completed by brazing (= lap joint) or by welding (butt joint).

For the lap joint process, a round hole is drilled in the pipe wall using a collaring head. After the tube wall is penetrated, two forming pins are extended from the drill bit. The collaring head then automatically withdraws from the main run pipe and forms a collar in readiness for the branch tube. The branch tube is located within the collar and finally the joint is completed by brazing. A brazing fixture, a bead or dimple (depth stop), on the tube end ensures that the tube will penetrate to the correct depth on the run tube.

The required collar height (i.e. lapping distance) must be three times the branch tube wall thickness to get the maximum joint strength. Normally lap joints are used on small diameter tubing applications, such as used in the HVAC, automotive and other industries.

The time needed for making an outlet using the T-Drill method varies from seconds to minutes, depending on the tube diameter and pipe material used. The complete collaring process is carried out on the outside of the pipe, as opposed to traditional methods in which tools are inserted into the pipe, which makes the tooling difficult to locate when long lengths of pipe are required.


  • Production cost reductions up to 80%
  • No costly inventories
  • Less wasted material
  • Remarkably faster through-put times
  • Improved product strength, flow and brazing characteristics
  • Only one brazed joint instead of three
  • Applicable to almost all malleable materials including stainless steel, CuNi, aluminium alloys and copper

Most commonly used in:


Butt Welded Joint

T-DRILL Collaring Method

Whenever two pipes need to be joined together, T-DRILL is the answer.

Tee Forming – Pipe Branching – Collaring

The T-DRILL process is a patented method of producing outlets for branch connections. Pipe branching by T-DRILL method is also called collaring, mechanical tee forming or simple T-DRILL tees.

Butt welded joint is typically used in the process piping and heavier industrial applications. It provides a better quality inside surface, which is needed, where good flow characteristics and cleanliness are important. The T-DRILL collaring process is a method of producing outlets for branch connections directly from the run material. The process from hole cutting to collar trimming is carried out in a single workstation in one set-up from outside the pipe and no access into the pipe is needed from the end of the pipe.

First an elliptical hole is milled in the pipe. Since more material is needed in the “stirrup” area to get a good collar height for butt welding, an elliptical hole is used as a pilot hole rather than a round hole, which is used in the lap joint. After the pilot hole is made, the forming pins of the collaring head are extended and the collar is formed. This is aided by automated lubrication and optimized forming. Then the collar is trimmed to the desired height and the branch pipe is connected to the run pipe by butt welding.

Typical applications areas are in food processing, pharmaceutical, pulp and paper industry, stainless steel piping systems, water treatment, shipbuilding and convential and nuclear submarines.


  • No costly inventories
  • Improved flow characteristics
  • Instead of three welded joints, only one simple weld joint is required
  • Remarkable faster through-put times
  • Minimized inspection cost
  • Less chance of leakage or call-backs
  • Can be used in any malleable material
COMPARISON: Welded Fittings vs T-DRILL Collaring & Flanging

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