The UNR thread was developed for fatigue resistant safety critical fasteners during the 1950s.
The UNR thread form applies only to external threads. Its design form is the same as that of the external UN thread except that the root is required to be rounded. UNR threads are applied most often to high volume commercial fastener threads produced by rolling
Per ANSI/ASME B1.12003 – paragraph 2.3.1: “The rounded root (UNR Thread)…reduces the rate of threading tool crest wear and improves fatigue strength over that of a flat root (UN) thread.”
UN = Basic Unified National thread series
UNR = Basic Unified National thread series with external thread controlled root radius
UNS = Special Unified National thread series
UNRS = Special Unified National thread series with external thread controlled root radius
UNC = Unified National Coarse thread series
UNRC = Unified National Coarse thread series with external thread controlled root radius
UNF = Unified National Fine thread series
UNRF = Unified National Fine thread series with external thread controlled root radius
UNEF = Unified National Extra Fine thread series
UNREF = Unified National Extra Fine thread series with external thread controlled root radius
External UNR threads per ANSI/ASME B1.1
paragraph 1.3: UNR threads have "a rounded root contour" at the minor diameter.
paragraph 2.3.1(a): "The root contour ... shall have a smooth, continuous, non-reversing contour with a radius of curvature not less than 0.10825318P at any point and shall blend tangentially into the flanks and any straight segment. At the maximum-material condition, the point of tangency shall be at a distance not less than 0.625H below the basic major diameter.”
For internal threads there is no UNR requirement. Use a standard UN thread plug gage.
THREAD RING GAGES:
The difference between a UNR and UN thread ring gage is marking only. The thread ring gages are identical. Although Thread Check Inc. can mark thread ring gages with the R designation, it is not a standard requirement. Use the same ring gages to check either the UNR or UN screw thread form. The amount of radius at the root of the UNR thread form is too small to require a modification of the standard UN thread form ring gages.
UNR Inspection Method for External Root Radius:
- Optical Comparator or Vision System
- Tri Roll thread comparator with minor diameter type 7 rolls ( 55° included angle ). The Tri Roll thread comparator may be more practical in a high volume production environment
Comments or questions regarding this article may be sent to firstname.lastname@example.org
Class "W" Full Form Master Setting Plugs gages are used to set Tri Roll Thread Comparators. Master Thread Setting plugs are manufactured to a go basic pitch diameter size. PITCH DIAMETER is the theoretical diametrical plane which passes through a thread at the point where the width of the thread tooth and groove are equal. The pitch diameter is measured by means of the universally recognized three wire method.
Class W tolerance master setting ring gages are used to set ITC – Internal Thread Comparators. Class W tolerance master setting ring gages are manufactured to a go basic functional diameter. FUNCTIONAL DIAMETER is the actual (measured) pitch diameter of a thread adjusted by the cumulative effects of lead error and angle error, which is always added to external threads and subtracted from internal threads.
BRASS THREADS (British Standard Brass)
BSB - Brass threads are used for brass tubing with a uniform wall thickness regardless of the tube diameter. 26 Threads per inch is the standard on all tube diameters.
The reason for using 26 tpi, is brass tube has a almost the same wall thickness irrespective of the outside diameter of the tube, therefore as BSW thread depths are determined by the threads per inch, a lower tpi would reduce the strength of the tube or cut right through it.
The included thread angle on all BSB threads is 55 degrees
Nominal sizes range from 1⁄8 to 2 inches.
Thread Check supplies a complete range of thread gages.
|Thread Form Data||Tapping Hole|
|Diameter||O/D||Core||Pitch||Depth||Radius||Effective Dia||T.P.I||Dec / Met / Frac|
On July 30th of 2014, ABS Quality Evaluations conducted a 1 day audit of Thread Check Inc. There were no major or minor non conformities found during the audit. This is the 5th year in row with zero nonconformities. This is a testament to our organization's commitment to customer satisfaction, employee empowerment and continuous improvement.
Reference ASME B89.1.17-2001
Attributes to be inspected
- Diameter – Use high magnification comparator or measuring instrument with adjustable measuring force. .0000020” resolution or better is required. Use a cylindrical anvil.
- Roundness – Use Vee anvil with 60 degree included anvil. Cylindrical masters and a normalizing plate are required.
Suggestions for improved accuracy
Calibrate only in the central middle half of the thread measuring wire.
Thread measuring wires are calibrated on a functional basis so as to compensate for deformation when the wires are being used.
- Wire diameter is measured with the wire placed over a cylindrical anvil of a known size by a flat round contact point.
- The effects of errors in roundness are determined by noting the changes in diameter measurement utilizing a vee anvil and taking measurements around and along the wire.
Refer to ASME B89.1.17-2001 for measuring force and contact point configurations.
Wires must be unrestrained during measurement. They should be held in place by the specified measuring contact force only.
The set of 3 wires in a set must be calibrated at the same time to ensure the commonality of size standard is met. Each wire in a set must have the same diameter within .000010”.
Handle all thread measuring wires with care. Wires should be handled with soft tip tweezers
Allow adequate time for thread measuring wires to normalize. Use a normalizing plate adjacent to the measuring equipment.
|Attribute||Normal Laboratory Conditions||Optimum Laboratory Conditions|
|Wire Diameter||0.000025”/ 0.00064mm||0.000015”/ 0.00038mm|
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BSPF = British Standard Pipe Fitting is an obsolete designation which has been replaced with the G-Series per ISO 228
BSPF was the thread marking per screw thread designation BS-2779. BS-2779 has been rescinded and should no longer be used. The new screw thread designation is specifies a G in front of the nominal diameter and is defined in ISO-228.
In March 2003, the British Standards Institute withdrew BS-2779 and replaced it with ISO-228 (technically BS-EN-ISO-228)
Example: G1/2 x 14 BSPP Go Thread Ring Gage - Class A
Class A is considered the standard tolerance. Class B is a loose tolerance twice the amount of Class A. Class B only refers to the No Go Thread Ring Gage
There are many drawings that call out British Standard Pipe (BSP) to refer the current G-series screw thread. It should always be confirmed as BSP may also be a shortened version of BSPT -British Standard Pipe Taper.
For more information on British thread gauging you may contact firstname.lastname@example.org or visit our website
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The electricity is produced from sunlight using what are known as photovoltaic cells. These cells are built into thin glass-like panels of silicon material that have been mounted on top of Thread Check’s facility. The panels produce electricity when exposed to sunlight. Solar Panel systems are extremely reliable with no moving parts and typically last 30+ years with no maintenance.
The electricity produced by the solar panels produce can either be directly used in their offices and factory or sent back to the utility company for credit. To accomplish this, the power coming off the panels goes through a device called an inverter. The inverter monitors the solar power system, conditions the power, and keeps track of how much electricity is produced and then feeds the power to the appropriate place.
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Pg Steel Conduit Thread Plug Gages per DIN 40431 Steel Conduit Thread Gauges
Pg Steel Conduit Threads are manufactured per DIN 40430 Steel Conduit Thread Dimensions.
The Steel Conduit Thread Plug gauges are manufactured per DIN 40431.
The Pg thread series is designed specifically for the thin wall cross section of the steel conduit. The thin wall thickness requires a shorter profile thread that will not break through the outside diameter of the steel conduit during the machining process. The Pg conduit thread form features an 80° included angle and a shorter profile than the 60° included angle found in the Unified National thread series and the Metric thread series.
Pg Steel Conduit Thread Gages per DIN 40431 Steel Conduit Thread Plug Gauges
The DIN 40431 standard for P1 steel conduit threads specifies the requirements for using Go thread plug gages and plain NoGo plug gages to inspect the conduit threads. The plain NoGo plug gage checks the minor diameter or crest of the thread and verifies that minimum material condition is met. The Go threaded plug works normally by ensuring the maximum material condition is met.
Using the Pg Thread Plug Gages:
The Go threaded plug gage must be capable of being screwed by hand without undue force over the full length of the threaded work piece.
The NoGo plain plug gage must not be able to pass over the threaded work piece
Contact email@example.com for more information
Pg Steel Conduit Threads are manufactured per DIN 40430 Steel Conduit Thread Dimensions.
The Steel Conduit Thread Ring gauges are manufactured per DIN 40431.
The Pg thread series is designed specifically for the thin wall cross section of the steel conduit. The thin wall thickness requires a shorter profile thread that will not break through the outside diameter of the steel conduit during the machining process. The Pg conduit thread form features an 80° included angle and a shorter profile than the 60° included angle found in the Unified National thread series and the Metric thread series. .
Pg Steel Conduit Thread Ring Gages per DIN 40431 Steel Conduit Thread Gauges
The DIN 40431 standard for P1 steel conduit threads specifies the requirements for using Go thread ring gages and plain NoGo ring gages to inspect the conduit threads. The plain NoGo ring gage checks the major diameter or crest of the thread and verifies that minimum material condition is met. The Go threaded ring works normally by ensuring the maximum material condition is met.
Using the Pg Thread Ring Gages:
The Go Threaded ring gage must be capable of being screwed by hand without undue force over the full length of the threaded work piece.
The NoGo plain ring gage must not be able to pass over the threaded work piece.
The .0025" Master Calibration Pin Gage is ideal for calibrating ultra-precise measuring equipment such as laser micrometers. The micro pin gage is supplied with ISO 17025 accredited calibration providing the actual measurement. The diameters of these pin gages are approximately half the diameter of a human hair.
- Thread Check Micro Pin Gage material is E52100 Tool Steel hardened to Rockwell C60-62.
- Thread Check Micro Pin gages are 2.00" in length with ends ground square
- Micro Pin Master Calibration Pin Gages are ground and lapped to a 5 micro finish or better
- Traceable to NIST and supplied with ISO 17025 accredited calibration
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Thread Check Inc.
900 Marconi Avenue
Ronkonkoma, New York 11779