The UN and UNR thread gauge are equal except that the roots of the outside thread gages are round formed with a radius of curve among .

1. Hat is the difference betweenUNthreadgaugesand UNRthread gauges?
The UN andUNR threadgauge are equal exceptthatthe rootsof the outside threadgagesare round
formedwitha radiusof curve among .109 and .145 timesthe pitch.The roundformedroot enhances
exhaustionpotentialcomparedtothe Unifiedthreadgauge form.
The designationstandardof UNRthreadgage wasmade duringthe 50s due tothe demandforfatigue
resistantprotection –significantfasteners.Almosteveryexternallythreadedfastenerproducersmade
UNR rolledthreadgagesratherthan plain UNthread gauges.
The UNR threadgage decreasesthe rate of threadingtool crestwearand enhancesfatigue strength
overthat of a flatroot UN threadgauge.
Internal ScrewThread
 There’snoUNR threadgaugesfor in-house.(Utilize justUN form)
 ANSI/ASMEB1.1 Para 2.3.2; (there’snointernal UNRthreadgage
 ANSI/ASMEB1.3; UNR threadsappliesjusttoexternal threads
External Screw Thread
Both UNR and UN gaugesare usedfor external threads.
 Outside UNR thread gauges
The round formed root outline… shall have a flat, non-reversing non-stop, contour with the dimension
of curve not less than .109P at every point and shall merge tangentially into the edges and some flat
segment. At the max material condition, the spot of tangency shall be at a distance not less than 0625H
underthe basicmajor diameter.
 Outside UNthread gauges
Unifiedthreadgaugeshave an optional orflatround formroot contourat the small length.UN thread
gauge has “a straightroot contour at the small length,but”a roundformedrootclear beyondthe .26P
smoothwidthof the fundamental profile iselective”…”todeal for a few threadinginstrumentcrest
wear.
Outside UNR gagesas per IFI,basic componentsof screw thread formation
UNR threadgageshave a one differentformUN threadgauges…a requiredrootradiuswithlimitations
of .109 to .145 timesthe threadgage pitch.The smallestlimitof radius.109P isthe biggestradiuswhich
can be adjustedintothe UN gage withouttroublingthe bottomcontentconditionof the exteriorprofile.
The max circle of .145P is the biggestradiuswhichcanbe housedwithoutreasoning theoretical
interferingwithaninside gage atitsmax material ailment.
Screw Ring Gages

2. It’s not compulsory that the thread gauges be pointed with UNR. The UN or UNR ring gauges can be
utilized to test either the UN or URN screw thread form. Since the rate of a radius at the root of the UNR
gage form is too small there’s no need for any special adoption of the standard UN thread for ring
threadgauges.
Screw Thread Plug Gages
Utilize the standardUN threadworkplusas there’snointernal (female) UNRthreadgage.
How to testthe root radius
 For lowrate applications,utilize anoptical comparatortotestthe UNR thread gage formroot
radiusat the small diameterof the external screw threadgage.
 For extreme rate applications,it’sfasteranda bitmore economical toutilize Gaugingsystem22
to monitorthe small diameter.