What tolerance standard for holes on 3D welding fixture table？

Global mainstream 3D modular welding tables adopt D10 hole tolerance(ISO 286-2)for locating holes,matched with H7 standard positioning pins.Two mainstream systems:D28(Φ28 hole,100 mm grid)and D16(Φ16 hole,50 mm grid).Below is the universally accepted industrial specification for export and technical quotation.

1.Hole Diameter Tolerance(D10)

D28 Series(Φ28 locating holes)

Nominal diameter:28 mm

D10 tolerance range:Φ28.065~Φ28.149 mm

Common simplified marking:Φ28 D10

D16 Series(Φ16 locating holes)

Nominal diameter:16 mm

D10 tolerance range:Φ16.065~Φ16.149 mm

Common simplified marking:Φ16 D10

Matching pin standard:Locating pins=h7 shaft tolerance,forming stable clearance fit for quick insertion&repeatable positioning.

2.Hole Pitch/Center Distance Tolerance(Critical for interchangeability)

D28 table:Grid pitch=100 mm±0.05 mm

D16 table:Grid pitch=50 mm±0.05 mm

High-precision cast iron premium grade:±0.03 mm(for robotic welding,high-tolerance batch production)

3.Geometric Tolerance Requirements

Position Tolerance of hole centers:

Standard grade:Position toleranceΦ0.08~Φ0.10 mm relative to table datum edges.

Premium cast iron table:Position tolerance≤Φ0.05 mm.

Hole perpendicularity to table surface:≤0.05 mm over 100 mm hole depth

Surface roughness of hole inner wall:Ra≤3.2μm

4.Grade Difference:Cast Iron VS Steel Table

Cast iron 3D welding table(HT250/HT300)

Standard specification:Hole D10;hole spacing±0.03~±0.05 mm;recommended for robotic welding,precision assembly.

Nitrided steel 3D welding table(S355/Q355)

Standard specification:Hole D10;hole spacing±0.05 mm;general fabrication standard.Low-cost steel tables may loosen tolerance to±0.10 mm,which causes poor accessory interchangeability.

5.Practical Buying&Technical Tip

If suppliers only state“precision holes”without tolerance grade,you must confirm D10 hole+pitch±0.05mm minimum.

If tolerances are wider than above:Clamps,positioning blocks and extension fixtures cannot be universally interchanged between different tables,and repeated positioning accuracy will fail.

Short English Specification Version(You can directly put on datasheet)

Hole tolerance:ISO 286-2 D10

System 28:Φ28 D10;Grid pitch 100±0.05 mm

System 16:Φ16 D10;Grid pitch 50±0.05 mm

Matching locating pin:h7

Hole position tolerance:≤Φ0.10 mm

Hole perpendicularity:≤0.05 mm/100mm