Double-J butt weld
Applied to joint
Butt joint — plates aligned end to end
Download
Shop
Equipment for groove welds
MIG and TIG machines suited for groove weld preparations on plate.
→ weldingandwelder.com
Description
A butt weld where one member is prepared with J-shaped grooves on both sides while the other member remains square. The double-sided J-prep combines single-side preparation economy with both-side welding benefits.
In plain English
One plate gets the curved J-prep on both top and bottom, the other plate stays square. It is the K-weld equivalent but with radiused grooves instead of straight bevels. Less common than the double-bevel K-weld because the machining is more expensive, but on thick T-joints where filler savings matter, it pays for itself. The arrow points to the plate that gets both J-preps.
Symbol position
Mirrored J symbols on both sides of the reference line. Arrow points to prepared member.
Size notation
Root radius, groove angle, root face for each side.
Notation examples
Broken arrow convention difference as per other single-member-prepared joints.
Broken arrow when needed. Each side dimensioned independently.
Broken arrow convention. Both sides dimensioned with 'r' and 'c'.
Common uses
- Heavy T-joints on very thick plate
- Cruciform joints where filler savings justify machining
- Thick corner joints with both-side access
- High-integrity structural connections
