--- title: "Work holding and tool mounting on lathe" subject: "Workshop Technology" chapter: 6 key: "semester_2/workshop_technology:lathe-work-tool-holding" source: https://www.bctengineer.com/q/semester_2/workshop_technology/lathe-work-tool-holding site: BCT Engineering --- # Work holding and tool mounting on lathe Workshop Technology · Chapter 6: General Machining Processes “Chip-forming” - Asked in: year not given, 6 marks - Video: [Work holding device in Lathe Machine I Tutorials- 05](https://www.youtube.com/watch?v=CUIjO60H_vc) — Learn Engineering Tutorials - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/workshop_technology/lathe-work-tool-holding - Whole chapter: https://www.bctengineer.com/md/semester_2/workshop_technology/chapter-6 ## Question Describe the devices used to hold work on a centre lathe. How are cutting tools mounted and set on the lathe? ## Short answer Work holding: three-jaw chuck for rounds, four-jaw for irregular, collet for precision, face plate for odd shapes, between centres with driver for long shafts, mandrel for bored parts, steady and follower rests for support. Tools are clamped in a tool post at centre height with minimal overhang and set square to the workpiece. ## Answer #### Work holding devices | Device | Description and use | |---|---| | Three-jaw self-centring chuck | Jaws move together by a scroll; holds round and hexagonal bars quickly; accuracy is moderate | | Four-jaw independent chuck | Each jaw moves separately; holds square, irregular or eccentric jobs; can be set accurately with a dial indicator | | Collet chuck | Split sleeve gripping small bars of exact size; very accurate, used in production | | Face plate | Large disc with slots; irregular jobs are bolted to it with clamps and angle plates | | Between centres | A job with centre holes is supported between the headstock (live) centre and the tailstock (dead) centre and driven by a lathe dog and driver plate; for long shafts | | Mandrel | A tapered rod pressed into a bored job so that the outside is turned concentric with the bore | | Steady rest and follower rest | Support long, slender jobs to prevent bending; the steady rest is fixed on the bed, the follower rest travels with the carriage | #### Mounting and setting of tools - The tool is clamped in the tool post (four-way turret post or quick-change post); the overhang is kept as small as possible for rigidity. - The cutting tip is set exactly at the height of the job's centre line, by checking against the tailstock centre, with a steel rule held against the job, or by a trial cut. A tool set above centre has less clearance and rubs; a tool set below centre has less effective rake and the work tends to climb over the tool. - Packing (shims) is placed under the tool to raise it; the tool must be firmly clamped. - The tool is set at right angles to the job for turning and facing; for threading, the tool is set square to the job with a thread gauge (centre gauge). - The depth of cut is set with the cross-slide dial, whose graduations show the tool movement; the reduction in diameter is twice the depth of cut. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which chuck should be used for square or irregular jobs that must be set accurately using a dial indicator? A. Three-jaw self-centring chuck B. Four-jaw independent chuck C. Collet chuck D. Mandrel Answer: B. Each jaw of the four-jaw chuck moves independently, allowing irregular and eccentric jobs to be centred. (Key point: Four-jaw chuck) 2. What supports a long, slender job against bending? A. Face plate B. Steady rest or follower rest C. Mandrel D. Collet Answer: B. Steady rests fixed on the bed and follower rests travelling with the carriage prevent bending. (Key point: Holding long slender jobs) 3. Where should the cutting tip be set? A. Well above the centre line B. Well below the centre line C. Exactly at the height of the job centre line D. Anywhere, as long as it is clamped Answer: C. Centre-height setting is needed for correct clearance and rake; wrong height spoils the cutting angles. (Key point: Tool height) 4. Which is correct for mounting tools and setting depth? A. Keep overhang large for visibility; diameter reduces by the dial reading B. Keep overhang small for rigidity; the diametral reduction is twice the depth fed C. Keep overhang small; diameter reduction equals the depth D. Overhang does not matter Answer: B. Short overhang gives rigidity; since the job is round, a depth of cut reduces diameter by twice that depth. (Key point: Tool overhang and depth of cut) ## Related in Workshop Technology - [Cutting tool materials and carbon steels](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Acutting-tool-materials-carbon-steels) — Workshop Technology, chapter 7 - [Thread cutting on lathe and change gears](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Alathe-thread-cutting-change-gears) — Workshop Technology, chapter 6 - [Classification and main parts of centre lathe](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Alathe-classification-main-parts) — Workshop Technology, chapter 6 - [Taper turning: set-over and compound angle](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Ataper-turning-setover-numerical) — Workshop Technology, chapter 6 - [Sheet metal cutting and forming operations](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Asheet-metal-operations-explained) — Workshop Technology, chapter 8 ## Related in other subjects - [Cutting tool materials and their properties](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Acutting-tool-materials-characteristics-economics) — Manufacturing and Production Processes, chapter 7 - [Alignment tests on a lathe](https://www.bctengineer.com/question.md?key=semester_3%2Fmetrology%3Amachine-tool-geometric-tests) — Metrology, chapter 13 - [Lathe operations, taper turning and turning calculations](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Alathe-operations-taper-turning-numerical) — Manufacturing and Production Processes, chapter 7 - [CNC lathe part program with G and M codes](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Acnc-lathe-part-program-gcode) — Manufacturing and Production Processes, chapter 9