Thread Limit Gauges


INTRODUCTION

It is wise to check the thread of connectors and adapters upon incoming inspection. Out of limits thread can create serious problems and may damage the connectors of mating components or ruin the connectors at the test equipment. Spectrum Elektrotechnik GmbH offers a comprehensive line of thread limit gauges to check the thread on a “GO” / “NO GO” basis.

 

RING GAUGE

The Gauge is used to check the thread of the female connector.

GO GAUGE
With this Gauge the pitch diameter, pitch angle and number of threads per unit are being examined. The gauge needs to thread on easily up to the very end of the threaded area, without having any force applied.

NO GO GAUGE
It must thread on no more than two revolutions. If the gauge does thread on, and without being forced, more than two revolutions, then the thread is below the allowable minimum limit, the thread pitch diameter is too small.

 

BOLT GAUGE

The gauge is used to check the coupling nut thread of the male connector.

GO GAUGE
The Gauge examines the pitch diameter, pitch angle and number of threads per unit. It needs to thread in easily, up to the very end of the threaded area of the coupling nut, without the need to have any force applied.

NO GO GAUGE
It must thread into the coupling nut no more than two revolutions. If the gauge does thread in without being forced, more than two revolutions, then the thread is above the allowable maximum limit, the thread pitch diameter is too big.

 

SET of GAUGES

A complete Set consists of two Ring Gauges and one Bolt Gauge and is supplied in an instrument case. The Gauges are available for each of the connector series, as listed below.

 

TERMINOLOGY

ISO METRIC THREAD
The thread is marked with the letter “M” for metric. The diameter and the pitch are in millimeters. The pitch is the distance from a point on the thread to a corresponding point on the adjacent thread. Example: M7 x 0.75 has a 7mm diameter and threads which measure 0.75mm from one point to its corresponding point.

PITCH DIAMETER
The pitch diameter is defined as the diameter of a cylinder that passes through the thread profile to make the width of the thread ridge and thread groove equal on both sides of the thread and parallel to its axis. The Pitch diameter is the primary control and reference datum for measuring threads.

TREAD DIMENSIONS
It determines first the kind of thread, either Unified Inch Thread or ISO Metric Thread and involves then functional size and pitch, and pitch diameter, including angle, lead and chamfer.

UNIFIED INCH THREAD
The thread is characterized by the diameter and the number of threads per inch. Example: 1/4”- 36 UNS has a 0.25” diameter and 36 threads per inch.

 

INSTRUMENT CASE LAYOUT

Thread Limit Gauges Layout/Filling

The actual layout and/or filling of the Instrument Case may differ from the schematic above. It depends on the sizes of the connectors and their threads, which results necessarily into the physical dimensions of the gauges. Some connectors are using the same thread, therefore these connector series can be checked with the same set of thread limit gauges.

 

LIST of SPARE PARTS

The table below shows in detail the threads, connector series and part numbers of the complete instrument cases. Additionally the model numbers of spare parts are listed, as no gauge may last forever or needs to be replaced because it was damaged by mistake.

Thread Connector
Series
Instrument
Case
P/N
Spare Parts
"GO"
Ring Gauge
P/N
"NO-GO"
Ring Gauge
P/N
Bolt Gauge P/N
M9 x 0.5 1.8/5,6 LG-M900-0500 GG-M900-0500 NG-M900-0500 BG-M900-0500
M7 2.4 mm LG-M700-0750 GG-M700-0750 NG-M700-0750 BG-M700-0750
1/4" 36 UNS 2.92 mm
3.5 mm
SMA
SPM
LG-Z250-36NS GG-Z250-36NS NG-Z250-36NS BG-Z250-36NS
11/16" 24 UNEF 7 mm
SC
LG-Z175-24EF GG-Z175-24EF NG-Z175-24EF BG-Z175-24EF
M29 x 1.5 7/16 LG-M290-1500 GG-M290-1500 NG-M290-1500 BG-M290-1500
3/4" 20 UNEF HN LG-Z750-20EF GG-Z750-20EF NG-Z750-20EF BG-Z750-20EF
5/8" 24 UNEF N LG-Z159-24EF GG-Z159-24EF NG-Z159-24EF BG-Z159-24EF
0.19" 36 UNS SSMA LG-Z190-36NS GG-Z190-36NS NG-Z190-36NS BG-Z190-36NS
7/16" 28 UNEF TNC
TNX
LG-Z111-28EF GG-Z111-28EF NG-Z111-28EF BG-Z111-28EF

 

THREAD SPECIFICATIONS

Connector
Type
Thread Pitch BOLT THREAD
(Dimensions in mm)
NUT THREAD
(Dimensions in mm)
Outer
Diameter
Thread
Pitch
Diameter
Inner
Diameter
max.
Outer
Diameter
min.
Thread
Pitch
Diameter
Inner
Diameter
max. min. max. min. min. max. min. max.
1.8/5.6 M9 x 0.5 .500 8.980 8.874 8.655 8.570 8.367 9.000 8.675 8.787 8.459 8.599
2.4 mm M7 0.750 6.978 6.838 6.491 6.391 6.058 7.000 6.513 6.645 6.188 6.378
2.92 mm 1/4"
36 UNS
0.706 6.327 6.187 5.867 5.791 5.563 6.350 5.892 5.994 5.588 5.766
3.5 mm 1/4"
36 UNS
0.706 6.327 6.187 5.867 5.791 5.563 6.350 5.892 5.994 5.588 5.766
7 mm 11/16"
24 UNEF
1.058 17.432 17.249 16.744 16.642 16.134 17.462 16.774 16.906 16.307 16.561
7/16 M29 x 1.5 1.500 28.968 28.732 27.994 27.844 27.128 29.000 28.026 28.226 27.376 27.676
HN 3/4"
20 UNEF
1.270 19.017 18.811 18.191 18.080 17.643 19.050 18.225 18.369 17.678 17.958
N 5/8"
24 UNEF
1.058 15.845 15.662 15.156 15.055 14.547 15.875 15.187 15.319 14.732 14.986
SC 11/16"
24 UNEF
1.058 17.432 17.249 16.744 16.642 16.134 17.462 16.774 16.906 16.307 16.561
SMA 1/4"
36 UNS
0.706 6.327 6.187 5.867 5.791 5.563 6.350 5.892 5.994 5.588 5.766
SSMA 0.19"
36 UNS
0.706 4.803 4.663 4.345 4.270 4.039 4.826 4.369 4.468 4.064 4.242
SPM 1/4"
36 UNS
0.706 6.327 6.187 5.867 5.791 5.563 6.350 5.892 5.994 5.588 5.766
TNC 7/16"
28 UNEF
0.907 11.085 10.919 10.495 10.404 9.972 11.112 10.523 10.640 10.135 10.338
TNX 7/16"
28 UNEF
0.907 11.085 10.919 10.495 10.404 9.972 11.112 10.523 10.640 10.135 10.338
Contact Details
Spectrum Elektrotechnik GmbH
Olschewskibogen 1
80935 Munich
Germany

Mailing address:
P.O. Box 450 533
80905 Munich

+49 (0)89 / 354 804-0
+49 (0)89 / 354 804-90

sales@spectrum-et.com
www.spectrum-et.com