# Sheet Metal & Fabrication Drawings

Source: https://dijitulmedia.co.uk/sheet-metal-and-fabrication-drawings/
Updated: 2026-10-12

> dijitul media produces sheet metal models, flat patterns and fabrication drawings for UK fabricators, engineers and product companies. We set bend radius and K-factor to suit your press brake, export 1:1 DXF flat patterns for laser, plasma or waterjet, and draw clear bend and weld details. Sheet metal CAD is £45 an hour + VAT, or a fixed quote.

Price: £45 an hour + VAT

## Problems this solves

- Folded parts come out a millimetre or two oversize on every bend
- Holes near bends stretch into ovals
- The laser cutter rejects your DXF or cuts every line twice
- Welders are working from a sketch and every frame comes out different
- Corners tear when folded because there is no bend relief

## Key facts

- 3D sheet metal models that unfold to accurate flat patterns
- Bend allowance calculated from your material, thickness, inside radius and K-factor
- Flat patterns exported as 1:1 DXF in millimetres, closed profiles, ready to nest
- Bend drawings showing direction, angle, sequence and inside radius
- Weld symbols to ISO 2553 on fabrication drawings
- £45 an hour + VAT, or a fixed quote per part or assembly

## K-factor, bend allowance and why your parts come out wrong

When metal is bent, the outside stretches and the inside compresses. Somewhere in between is the **neutral axis**, which keeps its length. The **K-factor** describes where that axis sits, as a fraction of the thickness from the inside face. Typical values fall roughly between 0.3 and 0.5, depending on material, thickness, inside radius and tooling.

The **bend allowance**, the length of material used in each bend, follows from it: bend allowance = bend angle in radians × (inside radius + K-factor × thickness). Get the K-factor wrong and each bend adds a small error, which on a box with four bends adds up to a part that does not fit.

The most reliable K-factor comes from your own press brake: bend a test strip of known length, measure the flanges and work back. If your fabricator has a bend table or preferred values, we use those; if not, we start from sensible defaults for the material and note them on the drawing so they can be corrected.

## Design rules that keep fabrication simple

- **Inside bend radius** at least the material thickness for mild steel and stainless, more for harder aluminium grades, matched to your available tooling.
- **Holes and slots kept clear of bends**, commonly at least 2.5 times the thickness plus the bend radius from the bend line, so they do not distort.
- **Bend reliefs** where a bend meets an edge, so corners do not tear.
- **Flange lengths** long enough to sit on the die; your press brake operator can tell you the minimum for each thickness.
- **One inside radius throughout** where possible, so the whole part bends with a single tool set.
- **Grain direction** noted for materials and finishes where it matters, such as brushed stainless.

## Flat patterns for laser, plasma and waterjet

The flat pattern is what actually gets cut, so it has to be right. Ours are exported as **DXF at 1:1 in millimetres**, with every profile closed, no duplicate lines, bend lines on their own layer (or removed, if your cutter prefers), and engraved part numbers on a separate layer if you want parts marked. Kerf allowance is left to the cutting company unless asked for, because it depends on their machine. Read more in 2D CAD drafting.

We also supply a bend drawing showing each bend's direction (up or down), angle, inside radius and suggested sequence, so the press brake operator does not have to work it out from the 3D model.

## Fabrication and weld drawings

Fabricated frames, guards, brackets and enclosures need drawings that show how pieces are cut, positioned and joined. Our fabrication drawings include a **cut list** of sections (box, angle, flat bar, tube) with lengths and end mitres, dimensions from clear datums, and **weld symbols to ISO 2553** showing weld type, size, length and which side. Notes cover material grade, finish (galvanised, powder coated, painted) and any post-weld machining. Drawings follow the general rules in technical drawings, including projection, tolerances and revision control.

Weld procedure, welder qualification and structural calculations remain the fabricator's or engineer's responsibility. We draw what is specified; we do not sign off structural adequacy.

## Materials and finishes on the drawing

A fabrication drawing should name the exact material, not just 'steel'. That means the grade and thickness, for example S275 mild steel, 304 or 316 stainless, or a named aluminium alloy and temper, because bendability, weldability and corrosion resistance all differ. Finish matters too: powder coating and galvanising add thickness, so close-fitting parts, threads and holes may need masking notes or extra clearance. We put material, thickness, finish and any masking on every drawing, so the cutter, folder, welder and finisher all work from the same information.

## Price

Sheet metal and fabrication CAD is £45 an hour + VAT. A single folded bracket with a flat pattern is a short job; an enclosure with doors, hinges and a drawing pack takes longer and is usually fixed-priced. Fabricators sending regular work can agree a standing process and file format. See prices or design for manufacturers.

## What you get

- Sheet metal 3D models and STEP exports
- Flat pattern DXFs for cutting, with bend lines on a separate layer
- Bend and fold drawings as PDF
- Fabrication and weld drawings with a cut list
- Assembly drawings with a bill of materials

## FAQs

### What K-factor should I use for sheet metal?

There is no single right value. Typical figures sit roughly between 0.3 and 0.5, varying with material, thickness, inside radius and tooling. The most reliable K-factor comes from a test bend on your own press brake. dijitul uses your fabricator's bend table where one exists and states the values used on the drawing.

### Can you supply DXF files for laser cutting?

Yes. dijitul supplies flat patterns as 1:1 DXF in millimetres with closed profiles, no duplicate lines and bend lines on a separate layer, ready for nesting. Tell us your cutting company's preferences for layers, colours and DXF version and we will match them.

### Why are my folded parts coming out oversize?

Usually because the flat pattern assumed the wrong bend allowance, either through an unsuitable K-factor or a different inside radius from the tooling actually used. Each bend adds a small error. Matching the model to the real press brake setup normally fixes it.

### Do you add weld symbols to drawings?

Yes. Fabrication drawings from dijitul use weld symbols to ISO 2553, showing type, size, length and side. Weld procedures and welder qualifications are the fabricator's responsibility, and structural design checks stay with a qualified engineer.

### Can you turn a sketch of a bracket into a cut-and-fold part?

Yes. Send the sketch with key dimensions, material and thickness. We model it as sheet metal, check bend radii and hole positions, and supply the flat pattern DXF and a bend drawing for the workshop, usually as a fixed quote.

## Prices and contact

Prices (all from, + VAT): Logo design £150; Brand identity pack £395; Business cards or letterhead £75; Flyer or leaflet £95; Brochure £295; Social media graphics pack £99; Photography, half day £295; Photography, full day £495; Product photography £25 per image; Video £695; 2D/3D CAD and design time £45 an hour. All prices are "from" and exclude VAT. Every job gets a fixed price before work starts. Printing, and travel for shoots beyond the Mansfield and Nottinghamshire area, are quoted separately. Contact: https://dijitulmedia.co.uk/contact/ · 01623 650333 · info@dijitul.uk