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/
How to determine the proper gagemaker tolerance for a GO/NO GO cylindrical gaging application.
One of our most frequently asked question is “Which gagemaker class of tolerance should be used for selecting plain plug and ring gages to check internal and external diameters of parts?”
The industry standard is referred to as the Ten Percent Rule. This common rule of practice requires that 10% of the product tolerance is divided between the GO and NO GO gauges. For plug gages a plus tolerance is applied to the GO member and a minus tolerance is applied to the No Go member. Ring Gauges receive the reverse tolerance direction so that the GO member is minus and the NO GO member is plus.
10 Percent Rule results in gauge tolerance always being included in the part tolerance by up to 10%. This rule results in the possibility that 10% of good product may fail inspection but that no bad product would ever pass inspection.
Example
A part has a hole diameter requirement of .500” +/- .001”. Thus the hole diameter is .4990” - .5010”. The product has a tolerance of .002”. 10% of the product tolerance is .0002”. Divide .0002” by 2 = .0001”. On the industry standard gagemaker chart, .0001” is classified as a class Z tolerance. The Go member would be specified as .4990” plus .0001” tolerance and the No Go would be specified as .5010”minus .0001”. The gage would be assembled and marked as .4990”- .5010” Class Z Go/No Go Plug Gage w/handle.
Selecting higher precision gagemaker tolerances for cylindrical plug and ring gages such as class X or XX will consume less product tolerance and will allow the acceptance of slightly more product but with less gage wear life and at greater expense.
Thread Check’s engineering staff can make recommendations in selecting the correct gagemaker tolerances for a given application.
Gage maker Chart
View our complete product listing of cylindrical products here
Master Setting Discs
Master Setting Discs are ideal for calibrating and setting comparators, snap gages and other precision measuring instruments. Master Setting Discs are furnished with insulating grips to prevent heat distortion from handling. They are available in gagemaker tolerances from class XX thru class Z. Master Setting Discs are offered in high quality tool steel, chrome and carbide materials for longer life. They are available in 3 styles for various applications. Master Setting Discs conform to ANSI B47.1. They are ring lapped to size, and polished. Roundness and taper of all gages does not exceed 50% of the applicable gagemaker’s size tolerance and are non-accumulative. Sizes are available up to 23 inches in style #3.
UPDATE ON ASME B1 THREAD COMMITTEE REPORT FROM AMTMA NEWS LETTER
The ASME B1 threads standards meeting was held May 13, 20l0 in Miami Beach Florida.
Following is the report on these meetings.
B1.1 60° product threads: new standard is available from ASME
The revised B1.2 is still in draft form at this time.
Sections have been reviewed and approved.
B1.5, acme threads: no new activity
B1.8, stub acme threads: will be revised soon
Bl-9, buttress threads: some changes proposed for symbols and wording.
BJ.20. pipe threads: David Kats brought up the issue of using 3 dimensional drawings in
the specification.
Angel Guzman stated he had not seen this in other documents. It was agreed if they need to be used to show a clearer picture, we would incorporate if possible. There was a discussion on the letter submitted by Guy Cuccio on changing of gage point from end of pipe to last scratch of thread. Guy passed out a copy of his proposed change for review. There was a discussion on the specification and whether to revise it. David Katz pointed out that section 8.1 refers to the "End of the Pipe" as the gauging reference. Section 8.1 and 8.2 refer to the "End of the Thread", but also refer to figure 6, which shows gauging to the end of the pipe. David Katz referred to the specification NI.5, section 1.7.2.1 which describes how to handle chamfer size on the product. It describes that the purchaser and supplier should agree on gauging points if chamfers exceed major diameter of the internal nd minor diameter of external, Alan Sheppard brought up the turns engagement method, Guy Cuccio stated that the turn's method is not an accurate way to check pipe threads. David Katz said this part of the Specification will be put in the appendix of the new revision.
It was discussed that some manufacturers' practice is to make large chamfers on external threads to protect the thread, especially on large fittings. They feel that the threads are good and the specification should allow this practice by not counting the excess of chamfer when gaging the parts. Additionally, this would better ensure adequate thread engagement. Some manufacturers have had auditors not agree with this practice because it is not allowed in the specification.
Al Barrows explained the following tasks that still needed to be done
• Review non-threaded gages in the current B1.2, table 12 items 8-16, table 13, items
8 thru 15 and table 14.
• Wording for progressive set plugs
• Wording for the calibration of the new vs. used gages
• Incorporate table 12,13 & 13 notes from current B1.2 document
• Integration of appendix A from current B1.2 document
B1.10 unified miniature screw threads: The Bl.l0-2004 unified miniature screw thread
document is current and available from ASME.
NEXT ASME B1 MEETING
October 19-21 2010 in St. Louis, MO
The American Measuring Tool Manufacturers Association is looking for new members. Visit www.amtma.com for information on becoming a member.
Dimensional Inspection of Parts Using Fixed Gages
Choosing the proper inspection instrument is a critical quality control decision; the wrong device or method could produce inaccurate results, and also affect the cost and performance of the parts that are inspected. Additionally, the parts should undergo a comprehensive inspection in which all aspects of the part's performance life and functions are considered. The importance of the part's function should directly correlate to how extensive an inspection might need to be performed, ranging from a simple scale to the utilization of complex measuring instruments.
It is also important to realize that when inspecting parts, gaging and measuring are two different terms. The primary distinction between the two relates to a count of units: gaging refers to whether the part features are within a specified limit, and measuring refers to the number of units in the specified dimensions of a part.
Measuring devices can be relatively costly and complex, but may be necessary depending upon whether an accurate count of units is needed. In contrast, gages are typically inexpensive, simple devices, and require little set-up. The choice of inspection devices (measuring or gaging) is usually determined by what type of measurement is needed. If the actual dimensions of a part are not required, then the less expensive gaging method is the optimal choice.
Benefits of Fixed Gages
Fixed gages are typically simple devices like plug gages or ring gages that contain no moving parts and are easy to use. As such, their use is very common. They are also easily portable, do not suffer breakdowns in service, and do not require power.
Because fixed gages are available in an extensive range of sizes and tolerances and offer increased assurance of a fit between mating parts, it is easy to see why fixed gages are the most widely used inspection device.
Setting Gages and Limit Gages
Fixed gages are usually regarded as either a Limit Gage or a Setting Gage. Setting Gages are used to set the zero position of a particular instrument, while Limit Gages determine either the maximum or minimum material condition of a part's features. 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, plug, and snap gages.
The Go, No Go Inspection Practice
In this gaging practice, a Go Gage is used, serving as the equivalent to one of the part's specified features. If the Go Gage fits into the part, then it stands to reason that the mating part does not have excessive material and will also fit, ensuring proper assembly. Likewise, if the No Go Gage does not fit into the part, it shows that the feature under inspection is not lacking material or is not too large and consequently too loose.
The Go, No Go Gaging practice is a quick, efficient, and cost-effective verification that part dimensions meet drawing requirements and will assemble and function properly.
Using Plain Plug Gages
Plug gages are available in many different types and are utilized for a variety of inspections. Reversible wire plug gages are held in a collet-type handle that forms either a single-end or double-end Go, No Go Gage Assembly. Reversible wire plug gages are available in a range from .004"-1.000", and in a tolerance range from class Z-XXX. Most often utilized for checking hole size, they can also be functional for setting masters, locating pins, calibrating laser micrometers, and other high precision demands. Wire type reversible plug gages also referred to as pin gages have become very popular, due to their low cost and availability in thousands of sizes.
To inspect hole size of a part, the Go gage is inserted into the hole. If the gage can be entered into the hole, then the hole is considered to be above its low limit. Following that, the No Go gage is used: if it enters the hole, than the hole is too big.
Using a series of plugs in various diameter steps will result in a high repeatability rate. Gaging should be performed under optimal conditions so as to have little effect upon the inspection, such as cleanliness of the part and proper temperature control. Work tolerance might also be a factor to consider, in which a gage wear allowance may be used. In this case, a wear allowance is added to the Go Gage diameter. A tolerance should be specified so that the total gage tolerance does not exceed 10% of the part tolerance.
For very fine tolerances, a carbide plus gage is often the most effective and practical gage to be utilized. Additionally, many gage users also elect to use plugs in addition to air gaging or electronic inspections, in order to ensure that the parts will mate.
For more information regarding fixed gages or any other gaging questions contact Thread Check ‘s sales engineering department.
Proper Care And Usage Of Gages
Part dimensions to be gaged should be cleaned and burr free to prevent gaging interference. Grit and part chips which become lodged in thread gages will create scratches and wear on the flanks of threads and on the outside and inside diameters of cylindrical plain gages. Various materials such as aluminum and castings are extremely abrasive and will tend to wear out gages more quickly than other types of materials. Finer pitch and smaller diameter thread gages tend to wear quicker than larger and coarser pitch gages and have less gage tolerance as well. Regarding thread gages, it only takes a small amount of wear to have a significant effect on the pitch diameter. The wear on each flank angle is multiplied by almost 4 times to determine the total impact of wear on the pitch diameter. 50 microinches or 1 micron of wear per thread flank will impact the measured size by .0002” which can be the total tolerance of many thread gages.
Selecting higher precision gagemaker tolerances for cylindrical plug and ring gages will consume less product tolerance and will allow the acceptance of slightly more product but with less gage wear life and greater expense. Thread Check’s engineering staff can make recommendations in selecting the correct gagemaker tolerances for a given application. The normal rule of practice requires that 10% of part tolerance be divided between the Go and the No Go gages. Applying this practice results in gage tolerance always being included in the part tolerance by up to 10%.This could result in the possibility that 10% of good parts may fail inspection but that no bad product would ever pass. Assuming that higher precision gagemaker tolerances are better, is not valid, and may create quality issues as these gages tend to wear quicker with the potential of becoming undersized and passing bad parts.
Gages should be turned or pushed slowly and gently into or onto the dimension being checked. Forcing gages will result in faulty gaging and the possibility of damaging both the part and gage. Spinning thread ring gages or thread plug gages onto or into parts will create greater friction and increased wear thus reducing the life of the gage.
Using hard chrome plated thread gages can extend the wear life by more than 100% over standard tool steel gages which can provide dramatic savings on replacement costs. Thread Check supplies all standard size thread plug gages in inches and metric up to 1 ½ or 39mm in diameter in hard chrome at no additional cost. Other options for coatings and alternate material for thread gages and cylindrical gages include tin coat, carbide, alternate steels and even ceramic. There are pros and cons to utilizing various coatings and materials in gage applications which should be discussed with your gage maker. For example, gages made of carbide and ceramic are extremely durable and have excellent wear properties, but can be extremely brittle and break and chip if not handled carefully.
A thin coating of gage lubricant will help reduce friction from gage to part.
Proper training of personnel involved in the use of gages will pay dividends on ensuring the gages are treated with care and last longer. Review the current inventory of gages and look for visual signs of nicks, dents and scratches on gage members and handles. Evidence of this may suggest the gages are not being handled properly.
The effects of thermal expansion should be taken into consideration on both the part and the gage.
The temperature of the part and the gage should be the same. 68° F is the ideal temperature at which both part and gage should be at when inspected because gages are calibrated at 68° F. This effectively eliminates any error due to thermal expansion.
Protecting gages from excessive heat, humidity, moisture and corrosive chemicals will extend the life of your gages. After use, gages should be cleaned and recoated with a thin-film rust preventative or dipped in an easy to peel oil-based waxed coating, and stored properly.
Gages should be periodically inspected and calibrated to assure accuracy. Go member gages tend to wear quicker with normal use. NOGO gages will wear on the ends that receive the greatest usage. Frequency of inspection and calibration should be dependent on such factors as the amount of usage, part and gage material, tolerance, and quality procedures
The major differences in common thread and cylindrical gage materials and coatings
All standard gages are manufactured from tool steel and hardened to 58 – 62 Rc
Chrome is a plating process that increases the hardness to 70-72 Rc. The Chrome process also reduces friction on the gage and prevents corrosion. There are many variables that effect gage life or wear but chrome can significantly extend the wear life of a gage by more than 100%. The typical cost to add chrome is usually 30% more than tool steel.
Carbide is a sintered metal with a harder but more brittle surface than chrome. The RC of carbide gages is 79-81 Rc.
Titanium Nitride (TiN) is a general-purpose coating for corrosion resistance and increased tool life. The Rc is approximately 85RC
When selecting alternate materials to tool steel it is important to consider the benefits to the additional cost.
