Definition
A consumable metal added during a welding or brazing operation to join two pieces of base metal. The filler material melts and fuses with the base metal (in welding) or flows between the joined surfaces by capillary action (in brazing) to form the completed joint. Filler material is supplied as welding rod, wire, or brazing rod, and its composition is selected to match or be compatible with the base metal being joined.
Plain English
The extra metal you add into a weld or brazed joint to fill the gap and bond the two pieces together. It comes as a rod or wire that melts during the process.
Context Anchor
Seen in aircraft maintenance instructions for welding, brazing, soldering, bonding, and structural repairs.
Why Pilots Care
Using the wrong filler material on an aircraft repair can produce a weak or brittle joint that fails in service. Approved repairs specify the exact filler to use so the finished joint has the strength and corrosion resistance of the original structure.
Intuition Check
Do not read this as any material used to plug a hole. In aircraft maintenance, filler material means the specified added material that becomes part of the completed repair or joint.
Example Sentence 1
The technician selected a filler material compatible with the 4130 steel tubing before starting the weld.
Example Sentence 2
Using the wrong filler material can cause the finish to crack after a few flights.