Thread Gage Seminar

Welcome to Productivity Quality, Inc.

PRODUCTIVITY QUALITY, INC.ADVANCED INSPECTION SERVICES, LLC (AIS) - A Division of PQI

ISO / IEC 17025 Accredited

Productivity Quality is ANABAccredited to ISO 17025

for the Calibration of thread plug gages and thread ring gages and many other things…

ANSI-ASQ National Accreditation Board

Morning Agenda• Thread basics• Go / NoGo thread gages• Handheld variable thread gaging

– Pitch micrometers– 3 Wire systems

• Optical thread measurement– Optical comparators– Video Measurement machines– Round part inspection systems

• 2D Contact thread measurement systems

Thread Form

Thread Nomenclature• Pitch Diameter - “located equidistantly between the sharp major & minor cylinders.”

•Major Diameter - “is an imaginary cylinder that would bound the crests of an external thread or the roots of an internal thread.”

•Minor Diameter - “is an imaginary cylinder that would bound the roots of an external straight thread or the crests an internal thread.”

• Per ANSI/ASME B1.7M

Thread Nomenclature(Layman's Terms)

•Pitch Diameter - is the halfway point between the sharp thread crest & root.

•Major Diameter - is the largest diameter of a thread.

•Minor Diameter - is the smallest diameter of a thread.

Thread Nomenclature(Illustrated)

Inch Thread Designations

External Inch Screw ThreadsNominal Diameter - Threads

per InchThread Series Class of Fit

.250 - 20 UNC 2A

Internal Inch Screw ThreadsNominal Diameter - Threads

per InchThread Series Class of Fit

.250 - 20 UNC 2B

Ring Gages & Set Plug Gages

Working Plug Gages

Special Nominal Diameter and Threads / Inch combinations or Pitch Diameters must be marked “UNS” per ASME B1.1-2003.

( Exceptions: “Before Plate” or “Before Heat Treat”.)

Metric Internal Thread Designations Metric Thread

Designater

Nominal Diameter x

Thread Pitch Tolerance Class Designations

M 6 x 1 4 H 6 HGrade Position Grade Position

Pitch Dia Tolerance Minor Dia Tolerance

Metric Thread DesignationsMetric External Thread Designations

Metric Thread

Designater

Nominal Diameter x Thread

Pitch Tolerance Class Designations

M 6 x 1 4 g 6 gGrade Position Grade Position

Pitch Dia Tolerance Major Dia Tolerance

Ring Gages & Set Plug Gages

Working Plug Gages

Special Nominal Diameter and Pitch combinations or Pitch Diameters must be marked “SPL” per ASME B1.13M-2005.

( Exceptions: “Before Plate” or “Before Heat Treat”.)

General Classifications For Inch Threads

Classes 1A and 1B Class 1A for external threads and 1B for internal threads. these classes are intended for ordnance and other special uses. They are used on threaded components where quick and easy assembly is necessary and where liberal allowance is required to permit ready assembly, even with slightly bruised hands or dirty threads.

General Classifications For Inch Threads

Classes 2A and 2B Class 2A for external threads and 2B for internal threads. are the most commonly used thread standards for general applications, including production of bolts, screws, nuts, and similar threaded fasteners.

General Classifications For Inch Threads Cont…

Classes 3A and 3B Class 3A for external threads and 3B for internal threads. provide for applications where closeness of fit, accuracy of lead, and angle of thread are important. They are obtainable consistently only with high-quality production equipment supported by a very efficient system of gaging and inspection. These fasteners are generally used in the aerospace industry.

General Classifications For Inch Threads Cont…

Thread Series There are three standard thread series in the Unified screw thread system that are highly important for fasteners: UNC(coarse), UNF(fine), and 8-UN(8 thread). Along with a special series designated UNS.

•Relationship of Internal and External Product Threads.

•Class of Fit = how tight or loose the product thread assembly is.

•Remember: The Product Dictates the Gages.

Attributes Gaging (Fixed Limit)Attributes Inspection is a non-quantitative type of

inspection whose only possible outcome is either accept or reject. Attributes Inspection is gaging at the limits of tolerance. In the world of Screw Threads, Go and No Go Ring and Plug Gages are the most common type of Attributes Inspection. Attributes Inspection is non generally recommended for SPC. , it cannot measure actual Pitch Diameter.

Product Thread Inspection

Fixed Limit GagesFixed Limit Gages determine either the maximum or minimum material condition of a part's features. Fixed Limit gages are typically utilized as a full-form or 3D simulation of the mating part. This serves as the basis for the gaging practice known as "Go, No Go," which is often used with ring and plug gages.

Purpose:

To Pass or Fail Product!They are not intended to give an

“Actual Size”.

USE:

“Fixed Limit Gages” provide a accurate, quick & economical

inspection of product specifications.

Thread Gages Are Not:

• Thread Chasers, Taps, Dies or Other Cutting Tools• Hammers•Die or Tap Clean Out Tools• Intended to Measure “Actual Size”

• Taper-lock Work Plugs (Standard)•Reversible Work Plugs (When Specified)•STI Taper-lock Work Plugs (When Specified)•Ring Gages • Setting Plugs Gages•Pipe Plug Gages •Pipe Ring Gages

Thread Gages Types

*Do not confuse a thread setting gage for a thread working gage

Taperlock Thread Plugs

Range: Inch = #0-80 UNF to 3-1/4-8 UN ( Chrome) Metric= M1.6 x .35 to M39 x 4.0 ( Chrome)

LH & RH Inch & Metric Threads in Stock.Materials: Chrome (Plated Tool Steel) 70/72 RC Tolerances: Class “ X”

Features:Go : Min Product Pitch Dia. No-Go : Max Product Pitch Dia.

Gage Tolerance: Plus Gage Tolerance: Minus Long Member Short Member

ANSI/ASME B1.2 (Inch) & B1.16 M (Metric)* Unless Otherwise Specified Taperlock is the Gage Design Supplied!!!

Catalog pg.# 33-81

Reversible Thread Plugs

Range: Inch = #0-80 UNF to 3/4 - 20 UNEF (Chrome) Metric= M1.6 x .35 to M18 x 2.5 ( Chrome)

Materials: Chrome (Plated Tool Steel) 70/72 RC Tolerances: Class “ X”

Features:Go : Min Product Pitch Dia. No-Go : Max Product Pitch Dia.

Gage Tolerance: Plus Gage Tolerance: Minus

•“Reversible” Must be Specified When Ordering!!!

Catalog pg.# 33-81

GO NOGO

Thread Ring & Set Plug GagesRange:Inch = 0-80 UNF to 3-1/4-8 UN (Steel & Chrome) Metric= M1.6 x .35 to M39 x 4.0 (Steel & Chrome)LH & RH Inch & Metric Threads in Stock.Tolerance: Class “X”Materials: Tool Steel 60/62 RC

Chrome (Plated Tool Steel) 70/72 RCFeatures:Go : Max Product No-Go : Min Product

Pitch Diameter Pitch Diameter Gage Tolerance: Plus Gage Tolerance: Minus Ring Knurled, No Groove Ring Knurled, Groove

Set Plugs - Both Members are the Same Length!!ANSI/ASME B1.2 (Inch) & B1.16 M (Metric)

Catalog pg.# 33-81

Save on Re-Calibration:

Purchase Set Plugs with Custom Rings!

Remember!!!

•Set Plug Gages are Only Intended to Inspect Thread Ring Gages. They are Not Used to Inspect Product Threads!

•Set Plug Gages Have the Same Pitch Diameters as the Thread Rings they Set, (Go PD Larger than NG PD).

Go / NoGo Thread Gages

• The Go gage should pass completely across or into the product threads.

• The NoGo gage for inch threads should stop within 3 turns. For metric threads, drag must be felt within 2 turns

Go / NoGo Thread Gages

• The accept / reject decision that was just made is based on a judgement of pitch diameter only. The thread gage has been ground with specific allowances to judge only the pitch diameter.

Variable Gaging (Fixed Limit)Variables Inspection is a quantitative type of inspection

whose we determine specific results for each thread parameter and compare it to a nominal and tolerance value standard for that thread per an accepted national standard

Product Thread Inspection

Pitch MicrometerLike the Go/NoGo gages, a pitch micrometer evaluates only the pitch diameter and returns a value that can be compared to a standard. For our 8-32 UNC 2B example the pitch diameter is .1399 – .1428”, a tolerance range of .0029”

Product Thread Inspection

Variable Thread Gages

Qualitative ReadingsThe Tri-Roll not only indicates whether a threaded part is within assigned limits, it also shows the exact position of the pitch diameter within a tolerance range. In addition, the Tri-Roll gages will check size and out of roundness of plain cylindrical parts.

Measuring Pitch Diameter by the Three Wire Method.

Thread Measuring Wires

Tolerance: .000020”

Sets Matched w/in.000010”

Material: Tool Steel 59/64 Rc

ANSI/ASME B89.1.17

Catalog pg.# 82 – 84

60 Degree Thread Measuring WiresPITCH DIAMETER = MEASUREMENT OVER WIRES (MOW) – CONSTANT w = Wire Size P =Pitch = 1 / # of Threads per Inch = The distance the Thread travels in one turn. C = Constant = 3w - .86602540P PD = Pitch Diameter = the halfway point between Sharp Major & Minor Diameters. Measured PD = MOW - ( 3w -0.88602540P) Reference ANSI / ASME Standards: B89.1.17 - 2001 “Measurement of Thread Measuring Wires”

Catalog pg.# 82 – 84

Choose Carefully!• Pee Dee Thread Wires• Mitutoyo 3 Wire Thread Measuring System

Optical thread measurement solutions provide variable data results enabling process control decisions. Optical solutions include:

Optical Comparators

Toolmaker’s Microscopes

Video Measurement Machines

Round Part Optical Measurement System

Optical Thread Inspection

Optical Comparators• Through the direct

measurement of edges

• Through the use of thread dedicated charts and overlays

• Typically more manual, operator dependent measurements

Optical Comparators• Larger systems enable

very accurate measurements from skilled operators

Video Measurement Systems

• Field of View edge processing for large sets of data points

• Powerful edge finding to eliminate foreign material

• High magnification and zoom lens capabilities

Video Measurement Systems

Video Measurement Systems

Video Measurement Systems• Lack of physical contact and force may effect results• Considerations for setting part to thread helix angle

Round Part Measurement Systems

Round Part Measurement Systems

2D Contact Thread Profile Measurement

Any Questions, Contact Us

Douglas Binning

doug.binning@pqi.net

763 249 8159

Tom Tremmel

tom.tremmel@pqi.net

763 249 8140

George Hatcher

george.hatcher@pqi.net

763 249 8141

PRODUCTIVITY QUALITY, INC. (PQI)

Custom Thread Gages

•Acme, Stub Acme, Buttress, UNJ, UNS...•Built to Your Specifications or Applicable Standards• Developed from Your Part Drawings • Designed to Meet Your Specific Needs• Drawings May Be Supplied, if Required.

ACME Thread Form

(All Created Drawings Require Your Approval!)

Buttress Thread Form

NPT PIPE GAGES

NPT L1 PLUG GAGE NPT L1 RING GAGETolerance: + or -one Turn from the notch.

Tolerance: + or - one Turn from the Small End Face of the Ring.

Catalog pg.# 86 - 87

•NPT Gages are Made to: ANSI/ASME B1.20.1

NPT PIPE THREADS

•NPT Threads are Considered “General Purpose” Pipe Threads.

•NPT Threads Are Intend to be Sealed at the Crest & Root with Teflon Tape, Pipe Dope or Other Types of Sealant.

•NPT Threads Do Not Require “Crest Check”, L3, or L2 Gages.

•NPT Gages are Made to: ANSI/ASME B1.20.1

NPTF PIPE PLUGS

NPTF L1PLUG GAGE

NPTF L3PLUG GAGE

CREST CHECK PLUG (6 Step ) GAGE

The L-1 Plug Inspects the Pitch Diameter of the Hand Tight (L-1) Length of Engagement.

The L-3 Plug Inspects the Taper and Wrench Tight (L-3) Length of Engagement.

The Crest Check Plug Inspects the Truncation Limits & Taper of the Minor Diameter.

Catalog pg.# 86 & 87

•NPTF Gages are Made to: ANSI/ASME B1.20.5

NPTF PIPE RINGS

The L2 Ring Inspects the Taper and Wrench Tight (L2) Length of Engagement.

The L1 Ring Inspects the Pitch Diameter of the Hand Tight (L1) Length of Engagement.

The Crest Check Ring Inspect the Truncation Limits & Taper of the Major Diameter.

NPTF L1RING GAGE

NPTF L2RING GAGE

CREST CHECK RING (6 Step ) GAGE

Catalog pg.# 88-89

•NPTF Gages are Made to: ANSI/ASME B1.20.5

NPTF PIPE GAGES•NPTF Gages are Considered “Dry Seal” Pipe Threads.

•NPTF Gages are Relationship Gages.

•NPTF L1 Tolerance is + or - One Turn from the, (Notch on the Plug or Small End Face of the Ring).

•NPTF L2 Ring, L3 Plug Tolerance is + or - One Half Turn from the Location of the L1 Gage.

•NPTF Crest Check Gage will be Between one of these Sets of Notches, ( MN & MNt ,B & Bt ,MX & MX t ). These Notches are in Relation to Where the L1 & ( L3 or L2 ) Gages Measured.

NPTF Classes of Product Threads

Class 1 Threads - “Acceptability is determined by coordinated use of L1 & L2 gages for external product threads and L1 & L3 internal product threads. Crest and root truncation is generally considered to be controlled by tooling or other means”. ANSI/ASME B1.20.5

Class 2 Threads - Same as above, “however, inspection of root and crest truncation is required.”, (ANSI/ASME B1.20.3). This means that 6-step root & crest check gages or other methods are required to inspect product root & crest truncation.

Dryseal Gage Selection ChartASME B1.20.5 - 1991 TABLE 1 Gages and Tolerances

Thread to be Gaged Gaged WithProduct Thread Tolerance

Applied to Basic Size [Note (1)]

Limits Method of Gaging [Note (1)] Tolerance

NPTF, ExternalL1 or L1 Short and [Note (2)]

L2 or L2 short ring gages

Plus (small) 1 turn

Minus (large) 1 turn

Threads are within the allowable tolerance when

the product reference point is on or between the

maximum and minimum step of the L1 gage.

PTF-SAE SHORT, External Plus (small) 0 turn

Minus (large) 1.5 turn

NPTF, InternalL1 or L1 Short and [Note (3)]

L3 or L3 short plug gages

Plus (large) 1 turn

Minus (small) 1 turn

PTF-SAE SHORT, Internal Plus (large) 0 turn

Minus (small) 1.5 turn

NPSF, InternalL1 or L1 Short plug gage

Plus (large) 0 turn

Minus (small) 1.5 turn

NPSI, Internal Plus (large) 1 turn

Minus (small) 0.5 turn

Notes:(1) Step limit gages with 4 (or 3) steps should be used.(2) The difference in engagement of the L1 versus the L2 ring gages shall not exceed 0.5 turn. See para. 1.8.4. (3) The difference in engagement of the L1 versus the L3 plug gages shall not exceed 0.5 turn. See para. 1.8.4.

Note: Customers usually prefer to measure Dryseal Straight Pipe Threads (NPSF, NPSI, …) with Go & No Go Plug gages. Go & No Go Plug gages may be used but, the parts must pass the NPTF L1 Plug gage.

Never force a Gage into or on a Part Being Check

Handle gages as you would any precision tool, misuse or mishandling can result in nicks or other deformities which can destroy the integrity of the gage.

Store gages in a secure location, preferably in individual compartments or containers. Gages should be dipped in an oil-wax based seal or coated with a rust preventive prior to storing

Ship gages packed separately, coated with rust preventive, with sufficient packing material to avoid damage.

Remember!!!

Any Questions, Contact UsPRODUCTIVITY QUALITY, INC. (PQI)

Metric Screw Thread Classes and Positions Cont…

The 'g' & 'H' are commonly confused with the unified method of denoting internal and external of 'A' & 'B'. Here the metric uses a method that is not present in the inch series.

The internal and external threads in metrics are denoted by the case of the letter used, lower case for external, and upper case for internal. The letter used denotes the amount of allowance adjustment applied to the basic size. For external threads, allowances available are 'e, f, g, & h'. For internal threads, allowances available are 'G & H'.

Here again we see a difference in the inch and metric systems. In the Unified, there is only one allowance available and it is only applied to the external thread. For metric, you can apply allowances to the internal also. In both the internal and external the 'h or H' signifies an allowance factor of zero. The 'G' is the only allowance for internal threads and the 'g' is the smallest allowance available for external, the 'f' being more, and the 'e' being the greatest allowance.

Metric Screw Thread Classes and Positions

Tolerance GradesGrades 4, 6, and 8, which reflect the size of the tolerance. Grade 6, the most common, is recommended for "medium" quality and normal lengths or general purpose threads. Grade 6 is the closest to the Unified Class 2A and 2B. Tolerances smaller than Grade 6 are recommended for "fine" quality or short lengths of engagement. Tolerances above grade 6 are larger and recommended for "coarse" quality or long lengths of engagement.

Tolerance PositionsExternal threads (bolts): small "e" = large allowance, small "h" =no allowance, small "g" = small allowance.Internal Threads (nuts): Large "G" = small allowance, Large "H" = no allowance.