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.
Three Wire thread Measuring Systems from Thread Check Inc
The traditional three-wire method is the most accurate method of measuring the effective or pitch diameter of an external screw thread. Unfortunately in the past, holding and correctly positioning three wires against a thread while simultaneously taking an accurate measurement had been an extremely difficult task. Now, Thread Check's 3-Wire Thread Measuring System provides a simple and precise way for determining the pitch diameter for threaded parts and thread plug gages. The system enhances Repeatability and Reproducibility ( R & R ) and reduces measurement time to a fraction of the time normally taken using the traditional three-wire method. Thread Check offers specially designed wire holders and wires and base assemblies that make thread measurement fast and accurate. Thread Check's holders are fitted with certified full length thread measuring wires that meet or exceed the requirements of the ASME/ANSI B1.2, and B1.16M, thread standards as well as ASME B89.1.17-2001, Federal Spec. GGG-W-366b and ISO standards. All wire holder sets include the actual wire size, NIST traceable number, and the constant required for determining the pitch diameter.
Thread measuring holders are precision made to predetermined thread pitches. The wires are held in a predetermined position by light pressure clips. The holders rotate freely on the spindle/anvil of the measuring instrument so as to engage the lead angle of a thread. Holders can be purchased without wires for companies that have existing wires. Wires can be easily installed. Thread measuring holders are available in a full range of Standard, Metric, and Acme sizes. Thread Check's engineering department can design wire holders for multiple start threads, helical gears, worms, and other special thread measurement applications. Thread measuring holders and wires available for a wide selection of measuring instruments.
Applications:
- Certify working thread plug gages & setplug gages
- Monitor the wear on working thread plug gages
- Monitor and control pitch diameter variation during thread fabrication
- Use in conjunction with “GO” and “NOGO” ring gages to control thread size to the most demanding specifications
- Determine out of roundness and taper that may exist in threaded parts
- Applications for preplating & postplating thread measurement
- Eliminate the cost and time involved in using outside calibration services
- Reduce measurement time to a fraction of the time normally taken using the traditional three-wire method.
PATENT NO. 5,317,809
PATENT NO. 5,383,286
FOREIGN PATENT
The Three Wire Method
The three wire method is recommended for universal use in the direct measurement of thread gages and components. It has been found to be the most accepatble and universally recognized method of measuring pitch diameter.
The pitch diameter is the diameter where the thread thickness is equal to the space between the threads. If the flats at the top and the bottom of the thread are the same, the pict diameter will coincide with the middle of the sloping side of the thread.
The pitch diameter is represented by the letter E
E=D - depth of thread = D - h
Reversible Style Thread Plug Gages.
Thread Check, Inc. offers a complete line of AGD – American Gage Design, metric working reversible style thread plug gages. The reversible thread plug gage style allows for one end of the gage to be rotated so the user gets two gages in one. A worn gage end can be turned around by simply opening the collet of the handle and turning the gage and bushing around so the opposite end essentially becomes a new gage. The reversible thread plug gage is ideal in high volume inspection applications. Thread Check’s reversible thread plug gages are manufactured per ANSI/ASME B1.16M. Thread Check, Inc. reversible style thread plug gages are manufactured to an X tolerance in class 6H. Reversible thread plug gages are available in M, MJ and specials. All standard reversible thread plug gages are stocked in hard chrome coating which extends the wear life of the gage by more than a 100% thus providing dramatic savings in replacement costs. All Thread Check, Inc. gages are manufactured to the high end of the tolerance to ensure longer gage life. Thread Check, Inc. manufactures reversible thread plug gages in carbide, ceramic and other types of specialty steels. Thread Check manufactures many types of special gages including pre-plates, multiple starts, special leads, acme threads, buttress threads, square threads, extra length thread gages, and custom gages to print. All thread plug gages are traceable to N.I.S.T.
Flex Hole Location Gages
Flexible hole location plug gages also referred to as centerline hole location plugs are used to determine the true centerline to centerline distances of threaded holes. The flexible hole location gage is slotted at 90° increments to ensure positive location on the thread flanks regardless of hole size. This feature provides a firm locating grip without pulling the shoulder of the plug up against the hole face thus avoiding any squareness error being transferred to the centerline measurement. The center is concentric to the threaded section within .0002” TIR for probe location of coordinate measuring machines as well as plate inspection setups as “overpin” measurements. The flexible hole location gage can also be used with vee blocks to check concentricity to other diameters. Thread Check stocks flexible hole location gages in unified and metric sizes. Special sizes and modifications to increase the post length can be priced on request.
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.
A New Power Driven Thread Gage
Multimatic Products recently developed a power driven thread gage to safely drive standard AGD go thread plug gages at a fraction of the price of some other types of units manufactured overseas in Germany. The power driven thread gages have been fairly popular in the automotive manufacturing industry for many years. The Rotary Thread Inspection Tool as Multimatic Products refers to it also checks thread dept up to approximately .7500 inches.
I have had the opportunity to work with the unit and the claims stating “reduced operator fatigue” are well founded in my opinion. I performed inspection on several hundred small .3125 inch coupling nuts and the tool performed soundly. The coupling nut featured a .250-36 UNS 2B thread with a thru hole depth of .3125. The gage powered through the part smoothly and then automatically reversed direction when it reached its thread depth. The gauging process was very simple and required no continuous hand turning. Conventional gauging would have required 11 turns of the standard thread plug gage into the part and then 11 turns to turn the gage out for a total of 22 turns per part. That adds up when inspectors are checking over 3000 parts per month or more!
I think this may be a ideal gauging solution for many companies and welcomed relief for the quality control inspectors.
For more information you can visit http://www.threadcheck.com/power-driven-thread-gaging/
The difference between taperlock style and reversible style thread plug gages
The taperlock thread plug gage style allows for a quick and convenient replacement of the gage member into an existing handle. A worn gage member can be simply removed and a new replacement inserted into the handle.
The reversible thread plug gage style allows for one end of the gage to be rotated so the user gets two gages in one. A worn gage end can be turned around by simply opening the collet of the handle and turning the gage and bushing around so the opposite end essentially becomes a new gage. The reversible thread plug gage is ideal in high volume inspection applications.
Both Thread Check’s reversible and taperlock style thread plug gages are manufactured per ANSI/ASME B1.16M ( metric ) or ANSI/ASME B1.2 ( inch ). Both styles of thread plug gages are manufactured to an X tolerance. Both styles are available in M, MJ , UNC, UNF, UNEF, J and specials. Reversible and taperlock style thread plug gages are stocked in hard chrome coating which extends the wear life of the gage by more than a 100% thus providing dramatic savings in replacement costs. All Thread Check, Inc. gages are manufactured to the high end of the tolerance to ensure longer gage life. Thread Check, Inc. manufactures both taperlock and reversible style thread plug gages in carbide, ceramic and other types of specialty steels. Thread Check manufactures many types of special gages including pre-plates, multiple starts, special leads, acme threads, buttress threads, square threads, extra length thread gages, and custom gages to print. All thread plug gages are traceable to N.I.S.T.
visit www.threadcheck.com for pictures of both styles
Understanding Tri-Roll & ITC Thread Comparator Systems
A variable thread gage system such as external and internal thread comparators can be an effective means of monitoring and controlling screw thread fabrication in high production environments.
The tri-roll comparator system provides a fast and efficient means of definitive thread inspection. Also, variable data output makes this gage a perfect statistical process control device. Routinely, the tri-roll thread comparator is used to analyze and distinguish the following characteristics: Functional diameter size, Pitch diameter size, Lead and/or flank angle deviation, Taper, and 120-degree out-of-round (lobing).
The functional size of a screw thread is defined as that diameter which relates the diameter effects of variations in the above characteristics as they apply to assembly with its mating part. In other words, it is the result of the cumulative effect of variations in these characteristics along the full length of engagement. Any variation in these characteristics will always cause the functional diameter of an external thread to increase, and in an internal thread to decrease. This diameter is commonly referred to as the Maximum Material Condition of the product thread.
Pitch diameter size is defined as an imaginary cylinder, concentric and parallel to the thread axis, at which the thread ridge and thread groove are of equal width. Pitch diameter is the predominant factor used in the control of size and fit of product threads. This measurement isolates one thread, disregarding the cumulative effect of variations of functional size. Therefore, it is proper to refer to minimum pitch diameter as the Minimum Material Condition of the thread.
Using the pitch diameter rolls (best wire radius or cone and vee) set the comparator with the same master used for functional size inspection. Place the product thread in the gage locating two full threads from the front. Rotate the part 120 degrees. Record the smallest reading. Repeat the process at the center and back of the thread. Record the smallest reading as minimum pitch diameter size. Record the difference of the three readings in the same plane as taper. Record the rotational T.I.R. as out-of-round.
Lead: The axial distance a screw thread moves when rotated about its axis one complete rotation. On a basic single start thread, the lead is equal to the pitch (1/TPI).
Flank Angle: The angle created by the thread flank and a line perpendicular to the thread axis. This is often referred to as the half angle of the thread.
The term drunken lead is a broad reference to variations in helical path. This must be added to the axial lead variation to obtain total lead variation.
Understanding Differential Analysis: Lead/Flank Angle
Deviation in lead/flank angle is inspected by comparing functional size and pitch diameter size. Theoretically, identical readings would indicate perfect lead and form. In actual practice, functional size is almost always larger than pitch diameter size. If the difference between the two is excessive the lead/flank angle variations inherent in the thread can cause problems with assembly or compromise integrity of fit. The value at which these variations can be termed excessive is usually dependent upon application. Military specifications for safety critical threads limit the acceptable differential to 40% of the total pitch diameter tolerance. However, as a general rule, 50% is sufficient for most commercial manufacturing.
Example: .375” – 24 UNF -3A
Min. P.D. .3479
Max P.D. .3450
Tolerance: .0029 x .50 = .0015 Max. allowable differential, functional diameter to pitch diameter with limit set at 50% of total pitch diameter tolerance.
Important notes:
1. No single gaging method can guarantee that a product thread will assemble and conform dimensionally. USE A GO THREAD RING TO VERIFY ASSEMBLY!!!
2. Avoid the production of thread parts in the upper or lower 15% - 20% of the pitch diameter tolerance. Most disagreements between gages and problems in assembly occur in these zones.
3. Do not turn product parts through the tri-roll as you would a thread ring. This will cause excessive and unnecessary wear on the gaging rolls, as well as prohibit consistent readings. Always lift the lever arm and index the part unless inspection requires rotation of the part.
4. Set roll screws so that rolls rotate without lateral movement.
CHROME THREAD PLUG GAGES REDUCE REPLACEMENT COSTS AND SAVE MONEY
Thread Check Inc. provides chrome plating on all standard sized thread plug gages up to 1 ½ in diameter typically for about the same price that other manufacturers charge for tool steel. The chrome process brings the Rockwell hardness up to 70-72 Rc from tool steel which has a hardness of 60-62 Rc. The Chroming of thread plug gages extends the wear life by more than 100% which provide dramatic savings on replacement cost. Wear issues that lead to undersize and out of tolerance gages are one of the major root causes for thread problems with suppliers and their customers. Thread plug and ring gages can wear within a day’s worth of inspection and cause misleading results creating scrap and rejections.
The frequency of calibration for any gage or instrument should be based on usage. If a thread plug gage is being used to check 200 pcs per hour I am fairly certain the gage will be undersize after just one day or even sooner. I would suggest having multiple gages on hand and a master gage that is used to settle internal disputes between production and final inspection. The most common wear issue involves the go member which takes the most amount of friction.
Create “USAGE and WEAR” charts for gages that are being used in high volume inspection.
Keep Thread Gages clean and lubricated to reduce friction and increase wear life.
The most common wear issue for thread gages involves the go member which takes the most amount of friction.
Thread plug gages can be easily checked for wear using a 3-Wire Thread measuring System.
Thread Ring Gages can be checked using a matching thread setplug gage.
