Joining
- Processes
- 18
- Families
- 2
- Column
- Tolerances
Thermal11
- Arc Welding±1/16 in (±1.6 mm) on welded assembly dimensions; ±1/32 in (±0.8 mm) with hard fixturing; tighter only by machining after welding
- Friction WeldingRotary: finished length controlled to about ±0.010 in (±0.25 mm) through upset control; FSW: butt gap under 10% of thickness, plate flatness governed by clamping
- Hot Plate WeldingAssembly height after welding ±0.010–0.020 in (±0.25–0.5 mm), controlled by a positive stop rather than by molded part height; meltdown 0.04–0.16 in (1–4 mm)
- Laser Plastic WeldingClamped joint gap ≤ 0.004 in (0.1 mm) required across the seam; quasi-simultaneous collapse controlled to about ±0.001 in (±0.025 mm)
- PCB Assembly (SMT Reflow)Placement accuracy ±0.001–0.002 in (±25–50 µm) at 3σ; stencil foil 0.004–0.006 in (100–150 µm) with aperture area ratio above 0.66; board bow and twist ≤ 0.75% per IPC-6012
- Power Beam WeldingBeam-to-seam alignment ±0.004 in (±0.1 mm); joint gap ≤ 0.004 in (0.1 mm) for autogenous welds; post-weld distortion roughly an order of magnitude below an equivalent arc weld
- Resistance Welding±1/32 in (±0.8 mm) on fixtured sheet assemblies; nugget diameter held to 4√t–5√t (t in mm); electrode indentation ≤ 20–25% of sheet thickness
- Soldering and BrazingJoint clearance 0.001–0.005 in (0.025–0.13 mm) for brazing, 0.003–0.005 in (0.075–0.13 mm) for soldering, specified at brazing temperature; assembly position set by fixture or self-locating features
- StakingFormed head height controlled to about ±0.005 in (±0.13 mm) by tool stop; hole-to-boss clearance 0.002–0.010 in (0.05–0.25 mm)
- Ultrasonic WeldingWeld collapse held to ±0.002 in (±0.05 mm) with distance-mode control; joint faces should be molded flat and parallel to the limit the tool allows
- Vibration WeldingMeltdown controlled to about ±0.004 in (±0.1 mm); final assembly height set by a positive stop or machine collapse control rather than by molded part height
Mechanical7
- Adhesive BondingBond line 0.005–0.010 in (0.13–0.25 mm) held with glass beads or shims; assembly position set by the bond fixture, commonly ±0.010 in (±0.25 mm)
- JoineryGlue line of 0.002–0.006 in (0.05–0.15 mm) for PVA; joints fitted to firm hand pressure rather than to a numeric tolerance
- Mechanical FasteningNormal-fit clearance holes about 1/32 in (0.8 mm) over nominal per ASME B18.2.8 for screws up to 1/2 in; preload scatter ±25–35% with torque control, ±15% with angle control, ±5–10% with bolt elongation measurement
- RivetingHole 0.003–0.006 in (0.08–0.15 mm) over nominal shank; driven head 1.5x shank diameter wide by 0.5x shank diameter high; SPR interlock commonly ≥ 0.016 in (0.4 mm) with ≥ 0.008 in (0.2 mm) remaining bottom sheet
- Timber Frame StructuresCNC-cut joinery to about ±1/16 in (±1.5 mm) over member lengths of 40 ft (12 m) and more; erection tolerances are set by the project specification
- Upholstery
- Weaving
About joining
Joining processes combine two or more parts into an assembly, either permanently (welding, brazing, adhesive bonding) or reversibly (fasteners, snap fits).
The design question is rarely which joining process is strongest, but which one tolerates the materials, thicknesses and access you already committed to upstream.