• March 24, 2023
  • Machine Tools
  • Cutting Tools
  • Software
  • Metrology
  • Accessories
  • Mechatronics
  • About us
  • Contact us
  • REGISTER
  • SIGN IN
www.cnctimes.com logo
  • News
  • CT+
  • Webinar
  • Knowledge Center
    • INDUSTRY UPDATES
    • INTERVIEWS
    • VIDEOS
    • TECHNICAL ARTICLES
    • CASE STUDIES
    • PRODUCT SHOWCASE
    • BLOGS
    • SUCCESS STORIES
    • NEWSLETTERS
  • Start Your Subscription
  • Register
  • Sign in

Information

Please login to give the feedback.

Subscription Plans

Subscription Type
Duration
Months
News
Articles
Blogs
Case Studies
Videos
Product Updates
Webinar
Amount
CT
Lifetime
Lifetime
Full Access
Limited Access
Full Access
Limited Access
Limited Access
Limited Access
No Discount
INR 0.00
CT+
6 Months
6 Months
Full Access
Full Access
Full Access
Full Access
Full Access
Full Access
5% Discount
INR 599.00
CT+
Annual
12 Months
Full Access
Full Access
Full Access
Full Access
Full Access
Full Access
10% Discount
INR 999.00

Subscription Plans

Subscription Type
Duration
Months
News
Articles
Blogs
Case Studies
Videos
Product Updates
Webinar
Amount
CT
Lifetime
Lifetime
Full Access
Limited Access
Full Access
Limited Access
Limited Access
Limited Access
No Discount
INR 0.00
CT+
6 Months
6 Months
Full Access
Full Access
Full Access
Full Access
Full Access
Full Access
5% Discount
INR 599.00
CT+
Annual
12 Months
Full Access
Full Access
Full Access
Full Access
Full Access
Full Access
10% Discount
INR 999.00
Successfully registered. Please check your email to activate account.

Registration
  • Sign In



Sorry Captcha Unsuccessful!!

Sign In


OR
If your not registered user first Register
  1. Home
  2. Blogs
  3. Global Dimensioning & Tolerancing

Global Dimensioning & Tolerancing

30 June, 2018
  • Tweet
  • share via email
Your comment has been posted.
We have sent you a verification email. To verify, just follow the link in the message.
Some technical error. Please try again.

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2018-06-30 19:50:00

What is Tolerance?

An acceptable amount of dimensional variation that will still allow an object to function correctly.

Few points to be known for Tolerances:

  • No manufacturing process is perfect – tolerances define the acceptable limits of dimensions
  • Tolerances should be based on the function of the part
  • Often, the tolerances will affect the manufacturing process that is chosen
  • Higher tolerances = higher cost
  • Specify dimensions only to precision and tolerance necessary for the part to function properly
  • Proper tolerancing ensures interchangeability – parts purchased from different vendors will function properly

 

Geometric Dimensioning & Tolerance

GD&T is a symbolic language used to specify the size, shape, form, orientation and location of features on a part.  It is a design tool that communicates design intent. It was created to ensure the proper assembly of mating parts, to improve quality, and to reduce cost. Geometric Dimensioning and Tolerancing (GD&T) is the way to accomplishing these objectives as defined by ASME (American Society of Mechanical Engineers) as Dimensioning and Tolerance ASME Y14.5M-1994 standard. Now, we also have an international standard that is ISO 1101.

Few points to be known for Tolerance:

  • Applying tolerances to dimensions is acceptable for parts that are not mass produced or do not mate with other parts.
  • Dimensional tolerance alone may not ensure that parts will function correctly, in more critical parts
  • Geometric Dimensioning and Tolerancing (GD&T) augments dimensional tolerances to control important geometric features.

 

For example, if only tolerance is applied without considering dimensioning then the part may fail. Hence global dimensioning is very crucial.

The following figures are from Shigley’s Mechanical Engineering Design, 10th edition, Budynas and Nisbett, McGraw Hill, 2015.

 

 

Figure 1

Fig1: Assume all the dimensions are in cm and we have the same tolerance (+/-0.01) in every single dimension, the result will be as shown in fig 2

Figure 2

Figure2: This part may meet all the dimensional tolerances of the previous figure but may not function correctly. We will witness deflection from everywhere. To rectify it, we can specify the deflection or the deformation with the GD&T symbols.

Also, the large “L” shaped figures in the figure 2 are known as Datum. It is basically used as a test jig, something that is defined as a perfect flat surface which can serve as a reference point for all the measurements.

Figure 3

Figure 3) There are several different kinds of geometric features to be considered during GD&T

  1. Size
  2. Location
  3. Orientation
  4. Form

Figure 4

Figure 4 Other than form controls, Datum is required for GD&T specification

We cannot say that the top surface is to be parallel without saying what it is parallel to – in this case the bottom surface is datum.

Figure 5

Figure 5 Datum designation on drawings. Three methods of designating a datum feature.

 

Figure 6

Figure 6 Features Control Frame

You can see various GD&T symbol applied for proper dimensioning.

We can generate the four geometric attributes of a feature as displayed in Figure 3 using the below table (Table 20 -1)

 

Why is GD&T so Important?

Geometric Dimensioning and Tolerancing (GD&T) was created to address the numerous issues that had been experienced throughout the years as associations endeavored to portray their part geometry. It is a "dialect" made out of images, used to productively and precisely convey geometric prerequisites for related highlights on components and assemblies. GD&T is vital to comprehend detailed engineering illustrations and has been effectively utilized by engineers, designers, and manufacturers in the automobile, aviation, electronics, and assembling ventures. It helps to specify and control the form, location, and introduction of the highlights of segments and fabricated parts.

The GD&T symbols for measurements on a section are characterized in connection to a datum—a hypothetically idealized point, line, or plane on a section that is utilized as a kind of the perspective point for tolerance calculations and dimensional estimations. The datum(s) on each part is viewed as the "zero point," and computations are worked starting from there and then to every other measurement. This is to guarantee the consistency of the part, giving manufacturing and measurement clarity to the design, production, and quality specialists. Furthermore, utilizing datums radically simplifies the design and specification procedures.

The currently used standards of ASME Y14.5M-2009 within the US and ISO 1101:2012 abroad have replaced previously complex and long descriptions with simple symbols. These symbols should be clearly and unanimously understood by everyone who reads and interprets an engineering drawing.

 

 

The Author: Avinash Pandey, MS Graduate in Mechanical Engineering & Management from University of Glasgow, UK, is a content writer at CNCTimes Pvt Ltd., the number one platform for channelizing resources. Having the audacity for learning about new technologies from the manufacturing sector, Avinash Pandey holds specialty in writing case studies, technical articles, technical blogs, and social media marketing content.

 

 

 

 

  • Follow @CNCTimes

Captcha is required.
Sorry Captcha Unsuccessful!!

Latest Blogs

  • 25 March, 2022

    Getting Closer to Launch: Additive Manufacturing for the Quadcopter Mold

  • 25 March, 2022

    Creating low-code solutions with big impacts

  • 24 March, 2022

    The Endless Possibilities of a Sim5x Machine

  • 24 March, 2022

    iMachining: The Revolution in Manufacturing

  • 24 March, 2022

    Your Way or the Swiss Way

  • 24 March, 2022

    SolidCAM- Integration, Association & Education

  • 23 March, 2022

    3D scan and CAD comparisons of large castings

  • 23 February, 2022

    Should You Invest in a Multitasking Machine?

  • 18 January, 2022

    Mastercam CNC machining capabilities for the medical industry

  • 19 April, 2019

    Additive Manufacturing: a big leap in production

  • 11 July, 2018

    Advanced Machining with Industrial Robots.

  • 14 August, 2017

    Industry 4.0 applications outside

  • 01 August, 2017

    Industry 4.0: Applications in a shop

  • 19 July, 2017

    Industry 4.0 – Machine monitoring

  • 09 June, 2017

    Drill helix angles and their applications

  • 24 May, 2017

    Achieving tolerance less than the accuracy: CNC

  • 17 May, 2017

    Key parts of a CNC fixture

  • 09 May, 2017

    Mohs scale and cutting tools

  • 11 April, 2017

    “OnCreate3D” First Full Cloud CAM app, introduces Stock Definition, modification and use in rouging toolpaths and many more features.

  • 10 April, 2017

    Epoxy granite beds in CNCs

  • 31 March, 2017

    HOW TO CREATE MACHINING OPERATIONS AND NC FILE OUTPUT FOR YOUR ONSHAPE MODELS

Previous Next

Related Blogs

  • 05 August, 2016

    Precision needs to be respected – Part 2

    Category: Measuring Instruments
  • 25 May, 2016

    The Concept of Measurement Accuracy

    Category: Metrology
  • 29 April, 2016

    What is Metrology?

    Category: Measuring Instruments

TESTIMONIALS VIEW MORE

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2019-11-19 17:57:22We would like to express our sincere appreciation for your service to us.You have provided us best marketing platform through CNCTime...

Mr.Adil Atar, Ass.Mng.Technical Sales & Service: Precision Machinekraft

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2016-10-21 09:00:00Dedication and determination is key to success and CNC Times team is evident to it - FARO Business Technologies (I) Pvt Ltd

Ms. Amrita Gokhale , FARO Business Technologies

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2016-08-25 00:00:00Seminar was really very good, please let us know about future seminars. we would like to attend the seminar on "Machining of the mate...

Roshan Deshmukh, Design Engineer - Ashvini Magnets Private Limited

FOLLOW US

TECHNOLOGY FOCUS

    Machine Tools

    • CNC Lathe
    • Boring Machines
    • Drilling Machines
    • Spark Erosion
    • Wire Cut
    • Vertical Machining Centers - VMC
    • Horizontal Machining Centers - HMC
    • Grinding Machines
    • Gear Cutting Machines
    • Additive Manufacturing - RP
    • Multi-Axis Machines
    • Multi-Tasking Machines
    • Welding Machines
    • Presses
    • Laser Cutting
    • Others
    • IIoT

    Metrology

    • CMM
    • VMM ( Vision Measuring Machines )
    • PCMM ( Portable CMM )
    • Measuring Instruments
    • Probing Technology
    • 3D Scanners
    • Roundness Measurement
    • Surface Roughness Measurement
    • Contour Measuring Machines
    • Others

    Accessories

    • Workholding
    • Toolholders
    • Spindles
    • Coolants
    • Others

    Software

    • CAD
    • CAM
    • CAE
    • ERP
    • Inspection Software
    • Reverse Engineering Software
    • MES
    • Others

    Mechatronics

    • Robotics
    • Automation
    • CNC Controllers
    • Others

    Cutting Tools

    • Turning Tools
    • Milling Tools
    • Grinding Wheels
    • Drilling
    • Others

INDUSTRY VERTICALS

  • General
  • Automotive
  • Aerospace
  • Healthcare
  • Healthcare Engineering
  • FMCG
  • Consumer Durable
  • Defence
  • Electronics
  • Oil & Gas
  • Heritage
  • Heavy Engineering
  • Die & Mold
  • Plastic
  • Footwear
  • Jobshop

PROFILE

  • About us
  • Contact us

Terms of use

  • Privacy Policy
  • Payment Policy
  • Refund Policy
  • Terms and Conditions

Follow us on:

Download CNCTimes App:

Play Store
2023 © www.cnctimes.com  | Payment Policy   |   Terms and Conditions
Developed & Maintained by Deven Infotech