--- title: "Sheet metal cutting and forming operations" subject: "Workshop Technology" chapter: 8 key: "semester_2/workshop_technology:sheet-metal-operations-explained" source: https://www.bctengineer.com/q/semester_2/workshop_technology/sheet-metal-operations-explained site: BCT Engineering --- # Sheet metal cutting and forming operations Workshop Technology · Chapter 8: Sheet Metal Works - Asked in: year not given, 6 marks - Video: [Sheet metal operations | operations performed on sheet metals | sheet metal processes](https://www.youtube.com/watch?v=jhBBEBDk4P4) — SELF ENGINEER - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/workshop_technology/sheet-metal-operations-explained - Whole chapter: https://www.bctengineer.com/md/semester_2/workshop_technology/chapter-8 ## Question Differentiate between blanking and piercing. Explain shearing, bending, rolling and punching operations of sheet metal work with sketches. ## Short answer Blanking: cut-out piece is product, die opening sized; piercing: cut-out is scrap, punch sized. Shearing cuts along straight line with blades. Bending forms sheet along axis, overbend for springback. Roling uses three rolls to curve sheet into cylinders. Punching removes slug to create hole (same as piercing). ## Answer Sheet metal is generally 0.4 to 6 mm thick; its operations are of the cutting and forming types. #### Blanking and piercing | Blanking | Piercing (punching) | |---|---| | Cutting the outline of a piece from a sheet | Cutting holes in a sheet | | The cut-out piece is the product | The cut-out slug is scrap | | Die opening is the size of the blank | Punch size is the hole size | | Clearance is applied to the punch | Clearance is applied to the die | | Example: coin, outside of a washer | Example: washer hole | #### Shearing Cutting a sheet along a straight line between two blades. A guillotine shear has a fixed lower blade and a moving upper blade, inclined at a small rake angle to lower the force. Hand shears (snips) cut thin sheets. ```text upper blade \ ============ \___ sheet lower blade ______| ``` #### Bending Forming a sheet along a straight axis by stressing it beyond its yield point. Air bending, V-bending and wiping (edge) bending are done in press brakes and dies. Springback occurs, so a slight over-bend is given. The minimum bend radius depends on the ductility of the material (about 1 to 2 times the thickness). ```text punch | v \ / \ sheet / sheet bent to a V \___________/ [ V-shaped die ] ``` #### Rolling A sheet is passed through three rolls (pyramid or initial pinch type) to form cylinders and curved shapes. Moving the top roll changes the curvature. ```text ( O ) top roll (adjustable) sheet ~~~~~~~~~~~~~ ( O ) ( O ) two bottom rolls ``` #### Punching A punch and die pair removes a slug to form a hole; it is used for holes, slots and notches. CNC turret presses punch many shapes. ```text | punch | |_______| ========| |======== sheet [ die ] slug [ die ] v ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In blanking, compared with piercing, A. The slug is the scrap B. The cut-out piece is the product C. The punch size is the hole size D. Clearance is applied to the die Answer: B. In blanking the cut piece is the product; in piercing the slug is scrap and the sheet with the hole is the product. (Key point: Blanking vs piercing) 2. In piercing, clearance is applied to the A. Punch B. Die C. Sheet D. Press frame Answer: B. Punch size gives the hole size, so the die is made larger; in blanking the punch is made smaller. (Key point: Clearance in piercing) 3. Why is a slight over-bend given in bending? A. To save material B. To compensate for springback C. To harden the sheet D. To make shearing easier Answer: B. After bending, the sheet partly springs back, so it is bent slightly more than required. (Key point: Springback) 4. Why is the upper blade of a guillotine shear inclined by a small rake? A. To lower the shearing force B. To make the cut curved C. To raise the force D. To hold the sheet Answer: A. The inclined blade cuts progressively along the length, reducing the force needed. (Key point: Guillotine shear) ## Related in Workshop Technology - [Blanking force and press capacity for washer](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Ablanking-force-press-capacity) — Workshop Technology, chapter 8 - [Basic forging operations](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aforging-operations-explained) — Workshop Technology, chapter 9 - [Drilling time and metal removal rate](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Adrilling-time-numerical) — Workshop Technology, chapter 5 - [Turning time and metal removal rate](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Alathe-turning-time-mrr-numerical) — Workshop Technology, chapter 6 - [Basic lathe operations](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Alathe-operations-explained) — Workshop Technology, chapter 6 - [Work holding and tool mounting on lathe](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Alathe-work-tool-holding) — Workshop Technology, chapter 6 ## Related in other subjects - [Blanking force, clearance and die sizes](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Ablanking-punching-force-clearance-numerical) — Manufacturing and Production Processes, chapter 6 - [Differentiate GVF, RVF and SVF with sketches](https://www.bctengineer.com/question.md?key=semester_4%2Fhydraulics%3Adifferentiate-gvf-rvf-svf-sketch) — Hydraulics, chapter 5, asked 5× - [Sheet bending allowance, force, springback](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Abending-allowance-force-springback-numerical) — Manufacturing and Production Processes, chapter 6 - [Painting work on metal surfaces](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apainting-metal) — Building Technology, chapter 9, asked 2×