Using a Go Thread Ring Gauge
It is always advisable to clean threaded parts before applying the thread ring to gauge part. If the radial slots in the ring gage accumulate chips and dirt, it is likely the parts have not been cleaned and /or the ring gage is being applied too harshly and removing material. Remember that a ring gage is a precision gage and not a die. The ring gage should not be used to re size over sized and defective product. The ring gage should turn over the part with very little force or drag. Many books state that the customary amount of pressure is 2 pounds of force but there is no specification or standard that dictates this.
On the whole it is suggested to turn the part onto the ring but this should be determined by the configuration and size of the parts. If the workpiece is large and heavy then of course the ring should be turned onto the part.
British Thread Gages – BSP Gages – BS EN ISO 228
G Series - Formally known as BSPF
The BSPP Thread Gages conform to to BS EN ISO 228-1 Parts and -2 for Gages. The standard year is 2003.
Screw Thread Plug Gages are to a standard class of fit. 
- British BSP Thread Ring Gages
Screw Thread Ring Gages are available in Class A and Class B
Class A on G Series rings is more common and considered standard. Class B only refers to rings, there is no class B on screw plugs
The go thread ring gauge is a class A only.Class B does not exist but you may get inquiries asking for a Class B go ring in which case we will mark the Class A as a class B.
The difference is only on the No go ring. Class A is a tighter tolerance than a Class B, The tolerance on a class B is twice that of the Class A.
In March 2003 the British Standards Institute withdrew BS-2799 and replaced it with ISO-228 ( technically BS-EN-ISO-228 )
Full Form British Thread Gages sold by Thread Check Inc are full form gages traceable to U.K.A.S
http://www.threadcheck.com/g1-8-x-28-bspp-go-no-go-thread-ring-gage-set/thread-gages-gauges/
Gagemaker Functional Thread Gages for large diameter thread inspection
The Gagemaker functional thread gage inspection equipment is ideal for large diameter internal and external thread inspection. The measuring equipment is relatively low cost, extremely versatile and readily available compared to Fixed limit thread ring and thread plug gages
Functional thread size gages inspect the effects of all thread element variations and report deviations (functional size).The gages use matched sets of precision ground thread rolls that seat in the threads during inspection to ensure accuracy. Each set of thread rolls is designed to ANSI specifications to measure unlimited diameters for a specific thread form. Common pitches ranging from 4 TPI to 20 TPI of the UN Series, ACME, and Stub ACME, and 1.5mm to 4 mm of the ISO Metric thread rolls are in stock. Whitworth and 7° X 45° Buttress thread rolls are available with a fast lead time. Custom thread rolls are priced on request.
The PG-6000 Series gages inspect diameters of internal threads. The RG-7000 Series gages measure diameters of external threads.
Special thread forms are priced upon request. All thread rolls are sold separately in matching sets.
Features
Measures internal or external threads for a range of diameters
Uses interchangeable thread rolls for measurement of different thread forms.
Replaces conventional ring and plug gages by providing actual diameter readings.
Provides functional measurement by inspecting the effects of thread element variations such as: lead, taper, thread height and pitch diameter.
Eliminates unnecessary damage to threads caused by ring and plug gages.
Durable construction allows use in a manufacturing or field environment.
Requires presetting using basic gage blocks, micrometers, or Gagemaker’s MIC TRAC measurement center.
http://www.threadcheck.com/functional-thread-size-gages/
Choosing The Correct Air Gage
Choosing the Correct Air Plug Gage
There are two basic styles of Air Plug Gages. Through Hole Style and Blind Hole Style. Dimension B on the attached form refers to the dimension of the jet centerline to the nose of the air plug. The overall dimension is indicated by Dimension “A”. If you are measuring a blind bore you must order a Blind Style air plug so the air escapement channels are designed to allow for air to escape the part, regardless of the depth of the bore. There is also an option for a Super Blind Plug which further reduces dimension B permitting checking closer to the counterbore, or the bottom of the part. If extra length is required and an extension or handle will not work, you can specify extra length in 1” increments. Non-Relieved style should only be specified for valve bores where obstructions like lands could make it difficult to remove the tool. You must also specify the dimensionair Model Number you are ordering the tooling for. It is always recommended to supply a part drawing with your inquiry.
http://www.threadcheck.com/images/pdf/Air-Plug-Form-2.pdf
Choosing the Correct Air Ring Gage
Special care must be taken when selecting air ring gages. There are 5 basic styles of air ring gages. The 5 styles are centered jets, offset jets, shoulder type, countered bore type, and snout type. Air rings may be attached directly to the Dimensionair, or used with base and guide chutes that can only be provided at time of manufacture. It is always recommended to supply a part drawing with your inquiry.
http://www.threadcheck.com/images/pdf/Air-Ring-Form.pdf
Measuring Plain External Diameters – American vs European
A case related to pin gages being rejected by our European Customer
The ASME B89.1.5-1998 is the correct document to review. Reference para. 6.1, pg. 5 & 6 as well as Table 4 on pg. 7. The values were computed using the equation in Puttock and Thwaite’s CSIRO Technical Paper #25. This statement is also on page 6. The question that should be asked is, what is their measurement uncertainty? Remember that the Europeans add measurement uncertainty into their measurements. We do not do that in the US. Depending on the uncertainty budget, they may not have the accuracy to measure a .000020” gage. Our measurement uncertainty is .000012” based on our latest accredited calculations . This is not good enough to accurately measure a Class XX pin. Our customers accept our measurements as long as our uncertainty is stated on the calibration certificates. According to ANSI/NCSL Z540 & ISO 17025 the total uncertainty of the measurement should not exceed 4:1. That would require a total measurement uncertainty of .000005”. The only lab that I know of that can measure this accurately w/in the 4:1 Rule, and prove it, is NIST.
See the link to the NIST web site that has a calculator to assist in the measuring force calculation.
http://emtoolbox.nist.gov/Elastic/Case10.asp
Note: The measuring force changes with the diameter of the part being inspected.
Thread Check Inc is now an authorized stocking distributor for Meyer Gage
Thread Check Inc. is your complete source for Class Z and Class X Pin Gage Sets and Libraries. With a wide assortment of pin gage sets and libraries manufactured by Meyer Gage, you will have everything you need conveniently stored in cases for all your measuring applications in both English and metric sizes. All Meyer Gage sets and libraries are manufactured in the USA under an ISO 9001 quality management system. All pin gages are traceable to NIST standards, and marked with sizes and serial numbers on both the boxes and the gages over .060”. Class Z pin gages are utilized for when you need to measure holes, locations or set instruments quickly and precisely. Class Z pin gages have tolerances of .0001” in inches and .0025mm in millimeters. Class X Pin Gage Sets are ideal for critical inspection needs and for maximizing Go/NoGo product tolerance limits. They have an inch tolerance of .00004” and a metric tolerance of .001mm. Browse our online catalog to find the Meyer Gages and pin gage sets you need, and to learn more about the features and benefits of each set.
http://www.threadcheck.com/class-z-and-x-pin-gage-sets-and-libraries/
New Measurement Uncertainty Requirements
Effective January 1st, 2012, all ISO/IEC 17025:2005 calibration laboratories are required to begin reporting measurement uncertainties for each measurement result. Fox Valley Metrology prides itself on being one of, if not the only lab to offer this via automated software. This automation allows us to provide this service at no additional cost.
For calibration laboratories, ISO/IEC 17025:2005 (clause 5.10.4.2) requires that “if a statement of compliance with a specification is made, this shall identify which clauses of the specification are met or not met”.
When compliance with a specification is made it should be clear to the customer which coverage probability for the expanded uncertainty has been used. Unless otherwise noted, the coverage probability will be 95%.
An explanation of In Tolerance, Out of Tolerance, and Within Uncertainty:
(Case 1) In Tolerance: If the specification limit is not breached by the measurement result plus the expanded uncertainty with a 95% coverage probability, then compliance with the specification can be stated. This can be reported as “In Tolerance”.
(Case 4) Out of Tolerance: If the specification limit is exceeded by the measurement result minus the expanded uncertainty with a 95% coverage probability, then noncompliance with the specification can be stated. This can be reported as “Out of Tolerance”.
(Case 2 & 3) Within Uncertainty: If the measurement result plus/minus the expanded uncertainty with a 95 % coverage probability overlaps the limit, it is not possible to state compliance or non-compliance. The measurement result and the expanded uncertainty with a 95 % coverage probability should then be reported together with a statement indicating that neither compliance nor non-compliance was demonstrated. A suitable statement to cover these situations would be “Within Uncertainty”.
Using a horizontal taper measuring block to inspect tapered plug gages
Thread Check Inc offers both horizontal and vertical tapered blocks specially designed to calibrate tapered plug gages. Instructions are referenced below.
INSTRUCTIONS FOR USE OF HORIZONTAL TAPER MEASURING BLOCK
In order to check the Major Diameter, the gage block setup is the small end major diameter divided by 1.000489. Then add the constant, marked on the block.
In order to check the Pitch Diameter, the gage block setup is the small end pitch diameter plus the best wire constant and that total divided by 1.000489. Then add the constant, marked on the block.
Place the block on the measuring device, with the back of the block against the floating anvil. Place the plug, to be checked, small end down. Move the plug into measuring position. You must now square the floating anvil to the measuring block. Turn the block slowly, first left and then right, until you achieve the smallest reading possible. When you reach the smallest reading, the block will be square. You may now take a measurement.
A hold down clamp has been provided but its use is not recommended unless necessary. The plug gages will sit on the small end without issue.
Calculating Pre Plate Screw Threads & Gages
It is important to understand how various plating affects manufactured parts featuring internal and external threads. All too often component parts are manufactured without taking into account the correct plating requirements. This results in rejection in final and incoming inspection or even in the field resulting in a recall. Either way proves to be very costly and time consuming.
Manufacturers of threaded components should understand the specific plating specifications and make specific allowances to the threads prior to the plating process. If this is not done or done incorrectly there is high probability that the thread will be too tight or too loose. This pre- plating allowance must be considered for both of the mating parts.
When working with the common 60 degree thread, the ratio is 4:1, meaning the plating thickness will build up 4 times the applied amount as each flank on both sides of the thread is affected.
The first part of making pre plate threads is to determine how much plating build up will be applied to the thread. This is determined by the plating specification as well as where the screw thread is located on the part. There may be cases where an internal thread is located deep down in a bored cavity and it may be difficult to apply the full amount of plating. It may be a good idea to discuss this with a qualified plating company.
To ensure the parts will assemble and fit correctly, the manufacturer should utilize pre plate thread gages so that the thread can be controlled correctly. This investment will pay dividends assuming the correct amount of plating is applied. This can be confirmed with standard or after plate thread gages. It may be a good idea to supply the plating facility with these gages so they can confirm that their plating process is correct and deliver back parts that are in tolerance.
Pre Plate Ratios for Various Threads
60° Unified thread = 4:1
29° Acme thread = 8:1
7°/ 45° Buttress thread = 4.3138:1
10° Square thread = 23:1
Based on the ratios above you can see how much affect a specific amount of plating can build up on a thread. There are several screw thread engineering programs that will handle the calculations for pre plating , including ThreadTech v2.24. You can download a free trial version of the ThreadTech software at www.threadcheck.com .
The rule for determining pre plate pitch diameters, major diameters, and minor diameters of parts and gages is as follows:
To determine pre plating dimensions for external threaded parts: For external threads subtract the max plating thickness from the parts high limit P.D.. Then subtract the minimum plating from the parts low limit P.D. For the minor and major diameters reduce the Parts maximum diameters by half the maximum plating and reduce the parts minimum diameter by half the minimum plating.
To determine pre plating dimensions for internal threaded parts: For internal threads add the max plating thickness to the low limit P.D. Then add the minimum plating thickness to the high limit P.D.. For minor and major diameters increase the minimum minor diameters by half the maximum plating and increase the maximum minor diameter by half the minimum plating.
To determine pre plating dimensions for thread ring gages: For thread ring gages subtract the max plating thickness from the P.D. of the Go thread ring gage. Then subtract the minimum plating from the P.D. of the No Go thread ring gage. For the minor diameter reduce the Go ring minor diameter by half the maximum plating and reduce the No Go ring minor diameter by half the minimum plating.
To determine pre plating dimensions for thread plug gages: For thread plug gages add the max plating thickness to the P.D. of the Go thread plug gage. Add the minimum plating thickness to the P.D. of the No Go thread plug gage. Increase the major diameter of the Go thread plug by half the maximum plating and increase the No Go thread plug major diameter by half the minimum plating.
Example for Thread Plug Gage:
Plating of .0002” - .0003” allowance per side multiple x 4
.0003 x 4 = .0012” Max
.0002 x 4 = .0008” Min
½ - 20 UNF 2B P/P
Basic Go P.D. = .4675” + .0012” = .4687” Go P/P pitch diameter
Basic No Go P.D. = .4731” + .0008” = .4739” No Go P/P pitch diameter
Basic Go Major Diameter = .5000” + .0006” = .5006” Go P/P major diameter
Basic No Go Major Diameter = .4948” + .0004” = .4952” No Go P/P major diameter
Example for Thread Ring gages:
Plating of .0002” - .0003” allowance per side multiple x 4
.0003 x 4 = .0012” Max
.0002 x 4 = .0008” Min
.0003 x 4 = .0012” Max
.0002 x 4 = .0008” Min
½ - 20 UNF 2A P/P
Basic Go P.D. = .4662” - .0012” = .4650” Go P/P pitch diameter
Basic No Go P.D. = .4619” - .0008” = .4611” No Go P/P pitch diameter
Basic Go Minor Diameter = .4446” - .0006” = .4440” Go minor Diameter
Basic No Go Minor Diameter = .4511” - .0004” = .4507” No Go minor Diameter
If no minimum and maximum plating thickness is given , then the given plating thickness is considered nominal or minimum plus 50% to determine maximum plating.
Thread Check Inc now offers a complete line of high precision feeler gauges
Our feeler gauges are widely used by many industries as gages to precisely measure clearances and gaps in machinery, dies, and component parts and as shims to accurately set spacing. They can be supplied in thicknesses ranging from .0005” up to .125” in various lengths and widths. They are conveniently available in 6" and 12" strips, 25' coils, as well as standard and custom blade sets. Our steel blades are offered in the highest quality carbon steel or stainless steel for outstanding resistance to corrosion and all blades are permanently marked with the thickness size for easy identification. The standard tolerance on all blades is +/- .0005" (+/-.0127mm). Tighter thickness tolerances of +/- .0001” are available if required. We also offer custom bending and stamping solutions to design a way around obstructions. The option of adding a step creates two gauges in one and can be used as a Go/No-Go gauge or for different applications. We commonly provide air gap gages for power and utility companies in 24", 36", and 48" lengths
Feeler Gauges are a close relative to plug gages. One of the most common applications of a feeler gage is for use with spark plugs on engines to establish the gap between the distributor points. Feeler gauges of 24", 36", and 48" lengths are also used by power and utility companies to inspect air gaps in their equipment. Stainless Steel feeler gauges are commonly used to check critical medical dimensional characteristics.
http://www.threadcheck.com/feeler-gauge-gage/
