2 Lots Within 10% Of Tolerance

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2 Lots Within 10% Of Tolerance Meaning
2 Lots Within 10% Of Tolerance Refers
2 Lots Within 10% Of Tolerance

Example for the DIN ISO 2768-2 tolerance table. This is just one example for linear tolerances for a 100 mm value. This is just one of the 8 defined ranges (30–120mm).

Whilst the GPDO allows for changes to buildings and land throughout England, there are some areas that are protected in certain permitted development rights. This is called Article 2 Land. For example Class M conversions, shops to residential, is prohibited in Article 2(3) land. This also affects items such as rear extensions on houses. These are broken down into two sections – Article 2(3. 1X CTS 300K Vintage-style dish back, SPLIT shaft audio taper potentiometers. Each pot comes with nut, lock & dress washer. These are a short shaft pots (threaded bushing is 1/4' tall & 3/8' diameter, fine spline 24-tooth shaft is 1/4' diameter). Unlike schedule tolerance and cost tolerance, scope tolerance is really hard to specify. Project tolerances are specified in the project plan, and they are typically between -10% (negative tolerance) and +10% (positive tolerance), which means, in the case of Cost Tolerance, that the project can cost 10% less or 10% more than initially planned. The value of a resistor with three bands is assumed to be within 20%. A silver 4th band = 10% tolerance, gold = 5%. A fifth band would indicate a 1 or 2% precision resistor. No guarantees that they will remain so over the years, and at least carbon comps and some dogbones certainly do not. Defects internal to the land shall not exceed 10% of the length or width of the land for Class 2 or Class 3 boards, or 20% for Class 1, and shall remain outside of the pristine area of the surface mount land. One electrical test probe ‘‘witness’’ mark is allowed within the pristine area for Class 1, 2 and 3.

Engineering tolerance is the permissible limit or limits of variation in:

a physical dimension;
a measured value or physical property of a material, manufactured object, system, or service;
other measured values (such as temperature, humidity, etc.);
in engineering and safety, a physical distance or space (tolerance), as in a truck (lorry), train or boat under a bridge as well as a train in a tunnel (see structure gauge and loading gauge);
in mechanical engineering the space between a bolt and a nut or a hole, etc.

Dimensions, properties, or conditions may have some variation without significantly affecting functioning of systems, machines, structures, etc. A variation beyond the tolerance (for example, a temperature that is too hot or too cold) is said to be noncompliant, rejected, or exceeding the tolerance.

Considerations when setting tolerances[edit]

A primary concern is to determine how wide the tolerances may be without affecting other factors or the outcome of a process. This can be by the use of scientific principles, engineering knowledge, and professional experience. Experimental investigation is very useful to investigate the effects of tolerances: Design of experiments, formal engineering evaluations, etc.

A good set of engineering tolerances in a specification, by itself, does not imply that compliance with those tolerances will be achieved. Actual production of any product (or operation of any system) involves some inherent variation of input and output. Measurement error and statistical uncertainty are also present in all measurements. With a normal distribution, the tails of measured values may extend well beyond plus and minus three standard deviations from the process average. Appreciable portions of one (or both) tails might extend beyond the specified tolerance.

The process capability of systems, materials, and products needs to be compatible with the specified engineering tolerances. Process controls must be in place and an effective Quality management system, such as Total Quality Management, needs to keep actual production within the desired tolerances. A process capability index is used to indicate the relationship between tolerances and actual measured production.

The choice of tolerances is also affected by the intended statistical sampling plan and its characteristics such as the Acceptable Quality Level. This relates to the question of whether tolerances must be extremely rigid (high confidence in 100% conformance) or whether some small percentage of being out-of-tolerance may sometimes be acceptable.

An alternative view of tolerances[edit]

Genichi Taguchi and others have suggested that traditional two-sided tolerancing is analogous to 'goal posts' in a football game: It implies that all data within those tolerances are equally acceptable. The alternative is that the best product has a measurement which is precisely on target. There is an increasing loss which is a function of the deviation or variability from the target value of any design parameter. The greater the deviation from target, the greater is the loss. This is described as the Taguchi loss function or quality loss function, and it is the key principle of an alternative system called inertial tolerancing.

Research and development work conducted by M. Pillet and colleagues^[1] at the Savoy University has resulted in industry-specific adoption.^[2] Recently the publishing of the French standard NFX 04-008 has allowed further consideration by the manufacturing community.

Mechanical component tolerance[edit]

Summary of basic size, fundamental deviation and IT grades compared to minimum and maximum sizes of the shaft and hole.

Dimensional tolerance is related to, but different from fit in mechanical engineering, which is a designed-in clearance or interference between two parts. Tolerances are assigned to parts for manufacturing purposes, as boundaries for acceptable build. No machine can hold dimensions precisely to the nominal value, so there must be acceptable degrees of variation. If a part is manufactured, but has dimensions that are out of tolerance, it is not a usable part according to the design intent. Tolerances can be applied to any dimension. The commonly used terms are:

Basic size: The nominal diameter of the shaft (or bolt) and the hole. This is, in general, the same for both components.
Lower deviation: The difference between the minimum possible component size and the basic size.
Upper deviation: The difference between the maximum possible component size and the basic size.
Fundamental deviation: The minimum difference in size between a component and the basic size.

This is identical to the upper deviation for shafts and the lower deviation for holes.^{[citation needed]} If the fundamental deviation is greater than zero, the bolt will always be smaller than the basic size and the hole will always be wider. Fundamental deviation is a form of allowance, rather than tolerance.

International Tolerance grade: This is a standardised measure of the maximum difference in size between the component and the basic size (see below).

For example, if a shaft with a nominal diameter of 10mm is to have a sliding fit within a hole, the shaft might be specified with a tolerance range from 9.964 to 10 mm (i.e., a zero fundamental deviation, but a lower deviation of 0.036 mm) and the hole might be specified with a tolerance range from 10.04 mm to 10.076 mm (0.04 mm fundamental deviation and 0.076 mm upper deviation). This would provide a clearance fit of somewhere between 0.04 mm (largest shaft paired with the smallest hole, called the Maximum Material Condition - MMC) and 0.112 mm (smallest shaft paired with the largest hole, Least Material Condition - LMC). In this case the size of the tolerance range for both the shaft and hole is chosen to be the same (0.036 mm), meaning that both components have the same International Tolerance grade but this need not be the case in general.

When no other tolerances are provided, the machining industry uses the following standard tolerances:^[3]^[4]

1 decimal place	(.x):	±0.2'
2 decimal places	(.0x):	±0.01'
3 decimal places	(.00x):	±0.005'
4 decimal places	(.000x):	±0.0005'

Limits and fits establish in 1980, not corresponding to the current ISO tolerances

International Tolerance grades[edit]

When designing mechanical components, a system of standardized tolerances called International Tolerance grades are often used. The standard (size) tolerances are divided into two categories: hole and shaft. They are labelled with a letter (capitals for holes and lowercase for shafts) and a number. For example: H7 (hole, tapped hole, or nut) and h7 (shaft or bolt). H7/h6 is a very common standard tolerance which gives a tight fit. The tolerances work in such a way that for a hole H7 means that the hole should be made slightly larger than the base dimension (in this case for an ISO fit 10+0.015−0, meaning that it may be up to 0.015 mm larger than the base dimension, and 0 mm smaller). The actual amount bigger/smaller depends on the base dimension. For a shaft of the same size, h6 would mean 10+0−0.009, which means the shaft may be as small as 0.009 mm smaller than the base dimension and 0 mm larger. This method of standard tolerances is also known as Limits and Fits and can be found in ISO 286-1:2010 (Link to ISO catalog).

The table below summarises the International Tolerance (IT) grades and the general applications of these grades:

IT Grade	01	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Measuring Tools									Material
Fits							Large Manufacturing Tolerances

An analysis of fit by statistical interference is also extremely useful: It indicates the frequency (or probability) of parts properly fitting together.

Electrical component tolerance[edit]

An electrical specification might call for a resistor with a nominal value of 100 Ω (ohms), but will also state a tolerance such as '±1%'. This means that any resistor with a value in the range 99–101Ω is acceptable. For critical components, one might specify that the actual resistance must remain within tolerance within a specified temperature range, over a specified lifetime, and so on.

Many commercially available resistors and capacitors of standard types, and some small inductors, are often marked with coloured bands to indicate their value and the tolerance. High-precision components of non-standard values may have numerical information printed on them.

Difference between allowance and tolerance[edit]

The terms are often confused but sometimes a difference is maintained. See Allowance (engineering)#Confounding of the engineering concepts of allowance and tolerance.

Clearance (civil engineering)[edit]

In civil engineering, clearance refers to the difference between the loading gauge and the structure gauge in the case of railroad cars or trams, or the difference between the size of any vehicle and the width/height doors, the width/height of an overpass or the diameter of a tunnel as well as the air draft under a bridge, the width of a lock or diameter of a tunnel in the case of watercraft. In addition there is the difference between the deep draft and the stream bed or sea bed of a waterway.

Notes[edit]

^Pillet M., Adragna P-A., Germain F., Inertial Tolerancing: 'The Sorting Problem', Journal of Machine Engineering : Manufacturing Accuracy Increasing Problems, optimization, Vol. 6, No. 1, 2006, pp. 95-102.
^'Thesis Quality Control and Inertial Tolerancing in the watchmaking industry, in french'(PDF). Archived from the original(PDF) on 2011-07-06. Retrieved 2009-11-29.
^2, 3 and 4 decimal places quoted from page 29 of 'Machine Tool Practices', 6th edition, by R.R.; Kibbe, J.E.; Neely, R.O.; Meyer & W.T.; White, ISBN0-13-270232-0, 2nd printing, copyright 1999, 1995, 1991, 1987, 1982 and 1979 by Prentice Hall.
(All four places, including the single decimal place, are common knowledge in the field, although a reference for the single place could not be found.)
^According to Chris McCauley, Editor-In-Chief of Industrial Press' Machinery's Handbook: Standard Tolerance '…does not appear to originate with any of the recent editions (24-28) of Machinery's Handbook, although those tolerances may have been mentioned somewhere in one of the many old editions of the Handbook.' (4/24/2009 8:47 AM)

External links[edit]

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Engineering_tolerance&oldid=970101642'

Printed Circuit Tolerances

FOR FABRICATION & ASSEMBLY

Have you ever submitted a Gerber file only to have a laundry list of feedback and red-pen markup sent back to you, creating hours of revisions and delays for the engineering team?

Delays like these not only increase the lead time of your product but increase costs, especially if special ordered materials are required for the adjustments.

Every PCB manufacturing facility has different PCB tolerances that affect an engineer’s target impedance and stack up.

While not mandatory, it is extremely beneficial for the PCB designer to consult the PCB manufacturer and PCB assembly shop as early as possible in the design and layout process to get a copy of the PCB tolerance requirements and stack up.

One of the benefits of working with a supplier like San Francisco Circuits is everything is managed under one roof - sales, engineering consultations, fabrication, component sourcing, and assembly.

Our specialty is in providing solutions to the most complex design challenges and ultra-demanding applications - be that high-heat, critical-reliability, or military standards.

We supply these advanced technologies to you, transforming the old way you would order printed circuit boards; with us, there is no more need to manage multiple supplier relationships and account for miscommunication on aspects like component overages or tolerances.

Get your PCBs Built-Fast.

OUR PCB TOLERANCES

During your design process, follow these printed circuit board tolerance guidelines to ensure the quality (and feasibility) of the manufactured PCBs is maximized.

All of our circuit boards are built within valid IPC guidelines and standards, typically IPC-A-600 Class 2 standards. We can also build HDI boards with smaller tolerances upon request.

Tolerances	Standards	Detailed Tolerance Standards
Inner Layer Clearances	0.010'
Pad Size	±20 %	IPC-6012 3.5.4.2.1 Rectangular Surface Mount Lands Defects such as nicks, dents, and pin holes along the external edge of the land shall not exceed 20% of either the length or width of the land for Class 2 or Class 3 boards, or 30% for Class 1, and shall not encroach the pristine area, which is defined by the central 80% of the land width by 80% of the land length as shown in Figure 3-6. Defects internal to the land shall not exceed 10% of the length or width of the land for Class 2 or Class 3 boards, or 20% for Class 1, and shall remain outside of the pristine area of the surface mount land. One electrical test probe ‘‘witness’’ mark is allowed within the pristine area for Class 1, 2 and 3. IPC-6012 3.5.4.2.2 Round Surface Mount Lands (BGA Pads) Defects such as nick, dents and pin holes along the edge of the land shall not radially extend towards the center of the land by more than 10% of the diameter of the land for Class 1, 2 or 3 boards and shall not extend more than 20% around the circumference of the land for Class 2 or 3 boards or 30% for Class 1 as shown in Figure 3-7. There shall be no defects within the pristine area which is defined by the central 80% of the land diameter. One electrical test probe ‘‘witness’’ mark is allowed within the pristine area for Class 1, 2 and 3.
Hole Size	Standard Plated ±3 mils - Advanced Plated ±2 mils - NPT ± 1 mil - NPT > 126 mils ±2+ mils
Printed Circuit Board Thickness	>=31 mils 10% or ± 3 mils which ever is larger - Thickness < 31 mils ±3 mils - Advanced 5%
Rout (Board Outline & Internal Cutouts)	Standard ±10 mils - Advanced ±5 mils - Special ±3 mils
Copper Trace Width/Spacing	±20 %	IPC-6012 3.5.1 Conductor Width and Thickness When not specified on the master drawing the minimum conductor width shall be 80% of the conductor pattern supplied in the pro-curement documentation. When not specified on the master drawing, the minimum conductor thickness shall be in accordance with 3.6.2.12 and 3.6.2.13. 3.5.2 Conductor Spacing The conductor spacing shall be within the tolerance specified on the master drawing. Minimum spacing between the conductor and the edge of the board shall be as specified on the master drawing. If minimum spacing is not specified, the allowed reduction in the nominal conductor spacings shown in the engineering documentation due to processing shall be 20% for Class 3 and 30% for Class 1 and 2 (minimum product spacing requirements as previously stated apply).
OVERALL BOARD FEATURES
Minimum Inside Radius	16 mils
Controlled Impedance	Standard 10% - Advanced 5%
Outer Copper Thickness	Absolute copper min. for 1/2 oz = 0.606 mils for 1 oz = 1.217 mils for 2 oz = 2.429 mils
Minimum Width Between Profile & Copper	5 mils
SCORING
PCB Dimension X/Y	10 mils
Scoring Depth	±3 mils on a 62 mil thick board
Rigid PCB Thickness	>=31 mils 10% or ± 3 mils which ever is larger - Thickness < 31 mils ±3 mils - Advanced 5%
Flexible PCB Thickness	±1 mils
Flexible Part Thickness	±1 mils
Flexible Part + Stiffener Thickness	±1 mils
BOW & TWIST
Bow & Twist Tolerance - with & without SMD	0.75%	IPC-6012 3.4.3 Bow and Twist Unless otherwise specified in the procurement documentation, when designed in accordance with 5.2.4 of IPC-2221, the printed board shall have a maximum bow and twist of 0.75% for boards that use surface mount components and 1.5% for all other boards. Panels which contain multiple printed boards which are assembled on the panel and later separated shall be assessed in panel form. Bow, twist, or any combination thereof, shall be determined by physical measurement and percentage calculation in accordance with IPC-TM-650, Method 2.4.22.

Figure 3-6 Round Surface Mount Lands

This image is Copyright 2019 by IPC International, Inc. and is used with IPC’s permission. This image may not be altered or may not be used by any other persons, companies or organizations other than the original user.

Note 1. Pristine area (80% of diameter).
Note 2. 2 Lots Within 10% Of Tolerance

Pin holes acceptable outside of pristine area.
Note 3. Electrical test probe 'witness' marks within the pristine area are acceptable provided the requirements for final finish are met.
Note 4. Defect ≤ 10% of land diameter ≤ 20% of land circumference for Class 2 or Class 3 and does not encroach pristine area.
Note 5. Solder mask.
Note 6. Clearance in mask.
Note 7. Solderable ball pad (land).

Figure 3-7 Printed Board Edge Connector Lands