PERFORATED METAL · DRAWING AND RFQ GUIDE

Perforated Metal Hole Size, Pitch and Ligament Guide

Perforated metal must be specified by more than hole diameter. A complete drawing identifies clear hole size, center-to-center pitch, straight or staggered pattern, ligament, orientation, sheet thickness, perforated zone, blank margins and tolerances before the sheet is formed into a filter component.

Direct Definitions

Hole size

The clear diameter or width of the opening, stated with shape and tolerance.

Pitch

Center-to-center spacing between adjacent holes in a stated direction.

Ligament

The remaining metal bridge between neighbouring hole edges.

Pattern and orientation

The row arrangement and its direction relative to the finished part or flow.

Perforated Metal Drawing Specification Table

Put dimensions and tolerances on one controlled drawing. If inspection is required, identify what is measured, where it is measured and the agreed sampling or acceptance method.

Drawing field	How to state it	Common ambiguity prevented
Hole shape and size	Round Ød, slot width × length, square side or drawing profile	Nominal designation without a measurable clear opening
Pitch	Center distance in each required direction	Confusing pitch with edge-to-edge bridge width
Pattern	Straight, 60° staggered or drawing-defined layout	Different open area and directional geometry
Sheet	Material, thickness, grain/rolling direction if critical	Assuming the same punching and forming behaviour
Perforated zone	Start/stop datums, blank margins and unperforated bands	Holes entering seams, bends, seals or mounting lands
Finished part	Cut size, bends, diameter, seam, flange and tolerances	Treating a flat sheet pattern as the complete component

Round-Hole Pitch and Ligament

For equal round holes measured along one pitch direction, the nominal metal bridge is ligament = pitch − hole diameter. This simple relation does not replace tolerance, burr, edge condition or forming review.

Use the perforated-metal open-area calculator for straight and staggered geometric open-area estimates. Finished filter open area will be lower when rims, seams, supports and blank margins mask the pattern.

Straight, Staggered and Directional Patterns

Straight rows

Hole centers align along principal directions; state both pitches if they differ.

Staggered rows

Rows are offset; identify the angle and reference direction on the drawing.

Slots and directional holes

State slot width, length, end form, row spacing and orientation to the part or flow.

Orientation survives into the finished part

When a perforated sheet is rolled, bent or cut, the hole-row direction moves with the blank. Reference the pattern to the cylinder axis, bend line, flange or another finished-part datum whenever orientation matters.

Sheet Thickness and Perforation Feasibility

Hole-to-thickness relationship

Small holes in relatively thick sheet may require a different process or feasibility review.

Material behaviour

Alloy, hardness and finish influence punching, burr and distortion.

Pattern density

Small ligaments and high open area reduce remaining material between holes.

Part dimensions

Large sheets, narrow strips and edge margins respond differently during perforating and forming.

There is no single hole-to-thickness ratio that safely defines every alloy, hole shape, tolerance and production method. Submit the complete drawing for feasibility review before fixing a critical design.

Blank Margins, Seams and Forming Zones

Keep controlled unperforated areas where the part requires a weld seam, rolled rim, flange, gasket seat, mounting hole, bend or reinforcement. Dimension the perforated zone from stable datums instead of describing it only as “full perforation.”

For cylindrical parts, compare the perforated filter tube and perforated filter cylinder pages.

Real Maidong Perforated Filter Components

These real Maidong parts show how perforated zones interact with forming, rims, flanges, seams, supports and finished geometry. They are examples, not universal dimensional limits.

Round-hole pattern

Opening-shape options

Fabricated filter forms

Flanged basket structure

Open Area, Strength and Filtration Are Different Questions

Geometric open area

Calculated from hole size, pitch and pattern before masked zones.

Structural behaviour

Depends on remaining metal, thickness, material, forming, supports and load.

Filtration opening

The perforated hole may be the coarse retention opening or only support finer mesh.

Finished pressure loss

Depends on area, thickness, layers, flow, fluid and contamination—not open area alone.

For a coarse support-core application, see perforated filter element support cores. For fine media selection, review stainless steel filtration mesh.

Perforated Metal Filter-Part Drawing Checklist

1. Define the opening

Hole shape, clear size, tolerance and inspection basis.

2. Define the layout

Pitch, pattern, orientation and perforated-zone datums.

3. Define the sheet

Material, thickness, finish and edge/burr requirement.

4. Define fabrication

Cut size, bends, rolling, seam, flange, supports and margins.

5. Define acceptance

Critical dimensions, quantity, drawings and required records.

Perforated Metal Hole, Pitch and Ligament FAQ

What is pitch in perforated metal?

Pitch is the center-to-center distance between adjacent holes measured in a stated direction. It is not the clear metal distance between hole edges.

What is ligament or bridge width?

Ligament is the remaining metal between adjacent hole edges. For equal round holes along the measured pitch direction, nominal ligament equals center pitch minus hole diameter.

Is hole diameter and open area enough to specify perforated sheet?

No. Also define pitch, pattern, orientation, sheet thickness, material, blank margins, part dimensions and tolerances. Different patterns can produce similar open area but different directional and fabrication behavior.

How does sheet thickness affect perforation?

Thickness affects punching feasibility, hole quality, distortion, forming and strength. A hole-to-thickness combination should be reviewed for the actual material, pattern, part size and process rather than assumed from a universal ratio.

What is the difference between straight and staggered hole patterns?

Straight rows align in both principal directions. Staggered rows are offset, commonly using a 60-degree layout for round holes. The drawing should identify the pattern and its orientation to the finished part.

What information belongs on a perforated filter-part drawing?

Show material and thickness, hole shape and clear size, center pitch, pattern and orientation, perforated zone, blank margins, part dimensions, bends or forming, seam, interfaces, tolerances, quantity and inspection requirements.

Need a Perforated Filter-Part Drawing Review?

Send material, thickness, hole geometry, pitch, pattern, margins, finished dimensions, forming, seams, interfaces, tolerances, inspection requirements and quantity.

Using This Reference in Procurement

A perforated-metal specification should state hole size, centre spacing and arrangement together. Pitch is a centre-to-centre distance; ligament is the material remaining between neighbouring openings. Record the pattern direction and reference area when comparing dimensions or open-area values.

Read a drawing before comparing open area

Check the nearest-neighbour direction

For a repeating row of equal round holes, the clear bridge between adjacent holes on that row equals the centre spacing minus the hole diameter. On staggered patterns, another neighbour direction may define the smaller bridge. Do not apply one row dimension to every direction without checking the layout.

Mark the reference region

A stated pattern open area generally concerns the repeating perforation field. The entire blank may also contain margins, internal solid zones and cut-outs. A further installed-area value can change again where supports, a seam or a gasket block the pattern. State which area your number describes.

Example: equal hole area is not equal component design

Compare the full geometry

Two blanks may have similar hole-area percentages but different hole sizes, arrangements and solid regions. They may also have different thicknesses and supported spans. Retain each geometric input on the drawing rather than reducing the enquiry to one open-area percentage.

Keep inspection and service separate

Hole and overall dimensions can be inspected against an agreed specification. A structural or pressure capability assessment needs its own loading, support, material and joint information. An open-area calculation is not a strength calculation or a certified flow-performance test.