In Gage Threadcheck's Official Blog

Go to Threadcheck
28Aug/14Off

UNR Screw Thread Form

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.”

Thread Designations:

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

Visit www.threadcheck.com

Comments or questions regarding this article may be sent to techsupport@threadcheck.com

27Aug/14Off

Master Thread Plug and Ring Gages for Thread Comparators

Master Setting Plugs For Tri Roll Thread Comparators

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.

http://www.threadcheck.com/tri-roll-thread-comparator.asp?pcFilter=tri-roll-thread-comparator-products

 

Master Setting Rings For  ITC-Internal Thread Comparators

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.

https://www.threadcheck.com/tri-roll-thread-comparator.asp?pcFilter=itc-comparator-and-gaging-segments-products

master setplug thread comparator
master set ring ITC comparator

27Aug/14Off

BSB Threads – British Standard Brass

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 18 to 2 inches.
Thread Check supplies a complete range of thread gages.

info@threadcheck.com

www.threadcheck.com

Thread Form Data Tapping Hole
Diameter O/D Core Pitch Depth Radius Effective Dia T.P.I Dec / Met / Frac
1/8" 0.125 0.0757 0.03846 0.0246 -- 0.1020 26 Number 47
1/4" 0.250 0.2007 0.03846 0.0246 -- 0.2254 26 Number 6
3/8" 0.375 0.3257 0.03846 0.0246 -- 0.3504 26 Letter Q
1/2" 0.500 0.4507 0.03846 0.0246 -- 0.4754 26 29/64"
5/8" 0.625 0.5657 0.03846 0.0246 -- 0.6004 26 37/64"
3/4" 0.750 0.7007 0.03846 0.0246 -- 0.7254 26 45/64"
7/8" 0.875 0.8257 0.03846 0.0246 -- 0.8504 26 53/64"
1" 1.000 0.9507 0.03846 0.0246 -- 0.9754 26 61/64"
1-1/8" 1.125 1.0757 0.03846 0.0246 -- 1.1004 26 1-5/64"
1-1/4" 1.250 1.2007 0.03846 0.0246 -- 1.2254 26 1-13/64"
1-1/2" 1.500 1.4507 0.03846 0.0246 -- 1.4754 26 1-29/64"

BSB Threads - British Standard Brass

Filed under: Thread Gages No Comments
11Aug/14Off

ISO 9001 Certification

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.