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School of Mechanical and Materials Engineering

MEEN 20060

Mechanical Engineering Design 1

Creo Computer Aided Design Project

2014/2015

Student Name: Alan Murphy

Student Number: 13360891

Date: 25/3/15

Design Title: Adjustable Spanner

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Design Title: Adjustable Spanner

1. Introduction

The aim of this project was to design a mechanical part or system using CAD (computer

aided design) software. In this case, the software used was Creo Parametric, running on my own

laptop. The first part of this project was started on the 21st of March and was completed by the 25th.

I chose to model an adjustable spanner, as I believed that it was suitably challenging to

design using CAD software, while at the same time containing few enough parts to not be overly

time-consuming. An adjustable spanner is a hand-held tool that can be used to grip objects of

various sizes for the purposes of twisting or tightening, as the jaws can be moved further apart or

closer together as needed.

The spanner consisted of three distinct separate parts, and while each part was modelled

from scratch, each of the parts required knowledge and techniques learned from previous design

exercises to complete. For example, all of the parts required basic knowledge of extrusions and

referencing, while a helical sweep was required to

model the adjustment screw. The use of a pattern

and a datum plane also aided in the modelling of

the movable jaw.

See to the right for a picture of the actual

spanner that this project was based on. All

measurements were taken with a ruler, and as

such are not accurate representations of the

actual dimensions of the spanner.

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2. Major component parts

Main Spanner Body: The largest part in this project,

consisting of the grip and the head, as well as a hole for

hanging the tool when not in use. Rounded to provide a

more comfortable and ergonomic grip, as well as to

remove any potentially dangerous sharp corners or stress

concentrations.

Movable Jaw: This jaw sits into the keyway of the main

spanner, and its position in relation to the fixed jaw can

be adjusted as required using the adjustment screw

(below). The grooves along the bottom of the jaw fit

around the adjustment screw and allow the jaw to

move as the screw is turned.

Adjustable Screw: Fits into the main body of the

spanner and is secured with a screw (aside from the notch where the screwdriver would turn the

screw, the screw is not detailed). Screw thread fits into the grooves along the bottom of the

movable jaw. When the screw is turned the jaw moves with it, allowing for the distance between

the fixed and movable jaw to be altered as needed.

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3. View of completed model

Pictured below are multiple views of the final piece, including a view of the entire model, an

exploded view and a close-up of where the movable jaw and adjustment screw interact.

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4. Drawing, Dimensions, Tolerances

Pictured below is a complete orthographic view of the spanner, as well as a detailed

engineering drawing of the movable jaw with dimensions and geometric tolerances.

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5. Discussions and Conclusions

Overall, the model turned out very well. No major issues arose during the modelling of the

spanner, and any small mistakes made were rectified with reasonably little difficulty. All the parts

fitted together as desired in the final assembly; however the movable jaw needed to be adjusted

manually to prevent clipping with the screw.

The main files for this project are as follows:

de4_spanner_body_finished.prt

de4_movable_jaw_finished1.prt

de4_adjustment_screw_finished.prt

de4_assembly_finished.asm

de4_drawing_finished.drw

de4_movable_jaw_geotol_finished.drw

A small difficulty arose with the Creo software when modelling the movable jaw. It was

desired that both jaws of the spanner have the same profile, for aesthetic as well as functional

purposes (any stress in the spanner while in use would therefore be equally distributed across both

jaws). However, as Creo does not allow two sketches to be open at the same time, even on different

parts, it became inconvenient switching between the sketches of both the movable jaw and the

main spanner body to ensure that the profiles were identical. This was a minor issue and did not

majorly impact on the project as a whole.

Given more time, I believe the adjustment screw could be modelled with extra detail. On the

actual spanner, there is a textured finished on the adjustment screw for increased grip, thus making

it easier to turn. The screw is also attached to the main body of the spanner with a smaller screw.

Further time would have allowed for the modelling of these details and resulted in a higher-quality

end result.