Optical Component Threading Adapters with M25 x 0.75 Threads


  • Integrate M25 x 0.75 Threaded Components with Other Industry Standard Threads
  • Adapters Available with Either Internal or External M25 x 0.75 Threads

LSM03

SM1A12

SM1L10

M25A1

External M26 x 0.706 (36 TPI) Threads and Internal M25 x 0.75 Threads

RMSA1

External M25 x 0.75 Threads and Internal RMS Threads

M32A1

External M32 x 0.75 Threads and Internal M25 x 0.75 Threads

SM1A12 Adapter Connecting a Scan Lens to an SM1 Lens Tube

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Interactive Selection Guide

M25 x 0.75-Threaded Optical Component Adapters

This page contains all of our Optical Component Thread Adapters that feature M25 x 0.75 threading. Adapters that have both internal and external threads are available, as well as adapters with two sets of internal threads or two sets of external threads.

Our M25 x 0.75 adapters are a subset of our entire line of optical component thread adapters. To view our entire line, please see our Interactive Adapters Selection Guide.

For use with microscope objectives, we recommend our brass microscope objective threading adapters; the brass construction is harder than aluminum which reduces thread binding.

Adapters with External M25 x 0.75 and Internal Industry-Standard Threads
Item # Typical Application External Threads Internal Threads
RMSA1
info
Integrate RMS Objective with
M25 x 0.75 Mount
M25 x 0.75 RMS (0.800"-36)
SM1A11
info
Integrate M25 x 0.75 Objective into
SM1 Lens Tube
M25 x 0.75 SM1 (1.035"-40)
M32A2a
info
Integrate M32 x 0.75 Objective with M25 x 0.75 Mount M25 x 0.75 M32 x 0.75
  • Threading types are laser engraved on these adapters.
Adapters with Internal M25 x 0.75 and External Industry-Standard Threads
Item # Typical Application External Threads Internal Threads
RMSA2
info
Integrate Scan Lens into RMS Mount RMS (0.800"-36) M25 x 0.75
SM1A12
info
Integrate Scan Lens into
SM1 Lens Tube
SM1 (1.035"-40) M25 x 0.75
M25A1
info
Integrate M25 x 0.75 Objective with M26 x 0.706 Mount M26 x 0.706
(36 TPI)
M25 x 0.75
M32A1a
info
Integrate M25 x 0.75 Objective with M32 x 0.75 Mount M32 x 0.75 M25 x 0.75
M32M25Sb
info
Integrate M25 x 0.75 Objective with M32 x 0.75 Mount M32 x 0.75 M25 x 0.75
SM2A33a
info
Integrate M25 x 0.75 Objective
into SM2 Lens Tube
SM2 (2.035"-40) M25 x 0.75
GCMA1a info Integrate M25 x 0.75 Scan Lens
into Galvo Mirror Mounting Adapter
SM2 (2.035"-40) M25 x 0.75
  • Threading types are laser engraved on these adapters.
  • This brass adapter has a flange to prevent overthreading the adapter or the objective into a microscope nosepiece. Brass is harder than aluminum which reduces thread binding.

Threading Specifications

The following is a general overview of screw threading. For more details regarding specifications and dimensions, please consult the Machinery's Handbook, available for purchase at many bookstores.

Features of a Thread
A thread consists of three repeating features: a crest, flank, and root (see drawing to the right). Except in special cases, threads have symmetrical sides inclined at equal angles when a vertical line is drawn through the center of a crest or root. The distance between corresponding points on adjacent threads is known as the pitch of the thread. The flank angle is defined as the angle the flank makes with a perpendicular ray drawn from the screw axis. Unless otherwise stated, threads have a flank angle of 30°, resulting in a total angle between flanks of 60°. Each feature is shown in the diagram to the right.

The major diameter is taken from the crests of a thread while the minor diameter is taken from the roots. For most screws, crests and roots do not terminate at a sharp point, so crest and root truncation values are included in the definitions of major and minor diameter. The pitch diameter is approximately halfway between the major and minor diameters.

Thread Form
A thread form is a set of rules that define the features' scale relative to one another. Common thread forms include the Unified Screw Thread Form, used in the United States of America and measured in imperial units, and the ISO Metric Screw Thread Form, used in many parts of the world and measured with the International System of Units. There are many thread forms in the Unified screw thread standard designated by either UN, which defines a flat root contour, or UNR, which defines a round root contour. These can be further described by appending more letters. For example, an extremely fine thread with a flat root contour is designated UNEF. Those forms which are not standardized by the Unified screw thread system are designated UNS.

Thread Series
Most screws are identified by their thread series. Thread series are denoted by the major diameter and density of threads. Unified threads specify density in threads per inch, while Metric threads specify the thread pitch. For example, in the Unified nomenclature, a 1/4"-20 cap screw has a 1/4" diameter barrel and the pitch is 20 threads per inch (TPI). In metric nomenclature, an M4 x 0.7 cap screw has a 4 mm barrel and the pitch is 1 thread per 0.7 mm. The term M4 x 0.7 is often shortened to just M4.

Unified Thread Class Tolerancing
Location Loose Optimal Strict
Internal 1B 2B 3B
External 1A 2A 3A
Metric Thread Tolerance Positions
Location Loose Optimal Strict
Internal - G H
External e or f g h
Metric Thread Tolerance Grades
Dimension Location Tolerance Gradesa
Minor Diameter Internal 4, 5, 6, 7, 8
Major Diameter External 4, 6, 8
Pitch Diameter Internal 4, 5, 6, 7, 8
External 3, 4, 5, 6, 7, 8, 9
  • The tolerance becomes looser as the grade increases. The underlined grades are used with normal lengths of thread engagement.

Thread Class
The tolerances and allowances on a thread series are given by a thread class. Unified thread classes are alphanumeric identifiers starting with a number from 1 through 3, where 1 is the loosest tolerance and 3 is the tightest, and either A for external threading or B for internal threading.

Metric threads have a slightly more complex tolerancing method that uses tolerancing grades, designated by a number 3 through 9; and tolerancing positions, which use letters e through h. Grades provide a measure of the tolerance itself: the smaller the number, the tighter the tolerance. Positions denote the distance of the tolerance from the pitch diameter. Uppercase positioning letters indicate internal threads while lowercase positioning letters indicate external threads.

Quoting from the Machinery's Handbook, 29th Edition, p. 1885: "To designate the tolerance class, the grade and position of the pitch diameter is shown first followed by that for the major diameter in the case of the external thread or that for the minor diameter in the case of the internal thread, thus 4g6g for an external thread and 5H6H for an internal thread. If the two grades and positions are identical, it is not necessary to repeat the symbols, thus 4g, alone, stands for 4g4g and 5H, alone, stands for 5H5H."

Thorlabs' SM Series Threads
Threading specifications for our SM threads, utilized in our lens tube and cage system components, are given below so that you can machine mating components to suit your application. Most SM series threads utilize a non-standard Unified thread form, indicated by the letters UNS, with a 30° flank angle and a thread class of 2A and 2B. The exception is our SM30 series thread, which is a Metric thread form with a 30° flank angle and a tolerance of 6H/6g. We also offer products with C-Mount and RMS threads, and the specifications for these threads are given below for reference. Please note that other manufacturers may have different tolerances for C-Mount and RMS threads. For other thread specifications that are not listed here, please contact Tech Support.

SM05 Threading: Ø1/2" Lens Tubes, 16 mm Cage Systems
External Thread, 0.535"-40.0 UNS-2A Internal Thread, 0.535"-40.0 UNS-2B
Max Major Diameter 0.5340" Min Major Diameter 0.5350"
Min Major Diameter 0.5289" Min Pitch Diameter 0.5188"
Max Pitch Diameter 0.5178" Max Pitch Diameter 0.5230"
Min Pitch Diameter 0.5146" Min Minor Diameter (and 83.3% of Thread) 0.508"
Max Minor Diameter 0.5069" Max Minor Diameter (and 64.9% of Thread) 0.514"
RMS Threading: Objective, Scan, and Tube Lenses
External Thread, 0.800"-36.0 UNS-2A Internal Thread, 0.800"-36.0 UNS-2B
Max Major Diameter 0.7989" Min Major Diameter 0.8000"
Min Major Diameter 0.7934" Min Pitch Diameter 0.7820"
Max Pitch Diameter 0.7809" Max Pitch Diameter 0.7866"
Min Pitch Diameter 0.7774" Min Minor Diameter (and 83.3% of Thread) 0.770"
Max Minor Diameter 0.7688" Max Minor Diameter (and 64.9% of Thread) 0.777"
C-Mount Threading: Machine Vision Lenses, CCD/CMOS Cameras
External Thread, 1.000"-32.0 UN-2A Internal Thread, 1.000"-32.0 UN-2B
Max Major Diameter 0.9989" Min Major Diameter 1.0000"
Min Major Diameter 0.9929" Min Pitch Diameter 0.9797"
Max Pitch Diameter 0.9786" Max Pitch Diameter 0.9846"
Min Pitch Diameter 0.9748" Min Minor Diameter (and 83.3% of Thread) 0.966"
Max Minor Diameter 0.9651" Max Minor Diameter (and 64.9% of Thread) 0.974"
SM1 Threading: Ø1" Lens Tubes, 30 mm Cage Systems
External Thread, 1.035"-40.0 UNS-2A Internal Thread, 1.035"-40.0 UNS-2B
Max Major Diameter 1.0339" Min Major Diameter 1.0350"
Min Major Diameter 1.0288" Min Pitch Diameter 1.0188"
Max Pitch Diameter 1.0177" Max Pitch Diameter 1.0234"
Min Pitch Diameter 1.0142" Min Minor Diameter (and 83.3% of Thread) 1.008"
Max Minor Diameter 1.0068" Max Minor Diameter (and 64.9% of Thread) 1.014"
SM30 Threading: Ø30 mm Lens Tubes
External Thread, M30.5 x 0.5 – 6H/6g Internal Thread, M30.5 x 0.5 – 6H/6g
Max Major Diameter 30.480 mm Min Major Diameter 30.500 mm
Min Major Diameter 30.371 mm Min Pitch Diameter 30.175 mm
Max Pitch Diameter 30.155 mm Max Pitch Diameter 30.302 mm
Min Pitch Diameter 30.059 mm Min Minor Diameter (and 83.3% of Thread) 29.959 mm
Max Minor Diameter 29.938 mm Max Minor Diameter (and 64.9% of Thread) 30.094 mm
SM1.5 Threading: Ø1.5" Lens Tubes
External Thread, 1.535"-40 UNS-2A Internal Thread, 1.535"-40 UNS-2B
Max Major Diameter 1.5339" Min Major Diameter 1.535"
Min Major Diameter 1.5288" Min Pitch Diameter 1.5188"
Max Pitch Diameter 1.5177" Max Pitch Diameter 1.5236"
Min Pitch Diameter 1.5140" Min Minor Diameter (and 83.3% of Thread) 1.508"
Max Minor Diameter 1.5068" Max Minor Diameter (and 64.9% of Thread) 1.514"
SM2 Threading: Ø2" Lens Tubes, 60 mm Cage Systems
External Thread, 2.035"-40.0 UNS-2A Internal Thread, 2.035"-40.0 UNS-2B
Max Major Diameter 2.0338" Min Major Diameter 2.0350"
Min Major Diameter 2.0287" Min Pitch Diameter 2.0188"
Max Pitch Diameter 2.0176" Max Pitch Diameter 2.0239"
Min Pitch Diameter 2.0137" Min Minor Diameter (and 83.3% of Thread) 2.008"
Max Minor Diameter 2.0067" Max Minor Diameter (and 64.9% of Thread) 2.014"
SM3 Threading: Ø3" Lens Tubes
External Thread, 3.035"-40.0 UNS-2A Internal Thread, 3.035"-40.0 UNS-2B
Max Major Diameter 3.0337" Min Major Diameter 3.0350"
Min Major Diameter 3.0286" Min Pitch Diameter 3.0188"
Max Pitch Diameter 3.0175" Max Pitch Diameter 3.0242"
Min Pitch Diameter 3.0133" Min Minor Diameter (and 83.3% of Thread) 3.008"
Max Minor Diameter 3.0066" Max Minor Diameter (and 64.9% of Thread) 3.014"
SM4 Threading: Ø4" Lens Tubes
External Thread, 4.035"-40 UNS-2A Internal Thread, 4.035"-40.0 UNS-2B
Max Major Diameter 4.0337" Min Major Diameter 4.0350"
Min Major Diameter 4.0286" Min Pitch Diameter 4.0188"
Max Pitch Diameter 4.0175" Max Pitch Diameter 4.0245"
Min Pitch Diameter 4.0131" Min Minor Diameter (and 83.3% of Thread) 4.008"
Max Minor Diameter 4.0066" Max Minor Diameter (and 64.9% of Thread) 4.014"

Posted Comments:
user  (posted 2019-05-28 17:37:25.987)
Dear Thorlabs Team, One reason we would like to use this M25x0.75 adapter is to mount the Olympus 20X water-dipping objective lens: https://www.thorlabs.com/thorproduct.cfm?partnumber=N20X-PFH However, the thread part of that objective lens is 5.8 mm long, while the internal M25x0.75 thread of this SM1A12 adapter is less than 5 mm long, which can affect the stability and parfocal length when we need to switch the objective on the microscope. Could Thorlabs adapt this one with a longer (i.e. deeper) internal M25x0.75 thread, so that the adapter lip can get in contact with the locating flange of the objective? Thank you very much! Best, Wenxuan
llamb  (posted 2019-05-29 10:31:54.0)
Hi Wenxuan, thank you for your feedback. This thread depth/length issue has been brought to the attention of our engineering teams, as there are varying thread lengths for our objectives with M25 x 0.75 threading that need to be accounted for. I have reached out to you directly to discuss the possibility of a custom thread adapter in the meantime.
thiel  (posted 2017-07-13 15:17:29.5)
Could I get a single adapter with diameter: M25 x 0.5 (inner) to M27 x 0.75 (outer) Could I get another single adapter with diameter: M25 x 0.75 (inner) to M27 x 0.75 (outer)
tfrisch  (posted 2017-07-28 02:18:09.0)
Hello, thank you for contacting Thorlabs. I will reach out to you with a quote.

Adapters with External M25 x 0.75 and Internal Industry-Standard Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RMSA1 Support Documentation
RMSA1Customer Inspired! Adapter with External M25 x 0.75 Threads and Internal RMS Threads
$20.99
Today
SM1A11 Support Documentation
SM1A11Adapter with External M25 x 0.75 Threads and Internal SM1 Threads
$21.86
Today
M32A2 Support Documentation
M32A2Customer Inspired! Adapter with External M25 x 0.75 Threads and Internal M32 x 0.75 Threads
$24.35
Today

Adapters with Internal M25 x 0.75 and External Industry-Standard Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RMSA2 Support Documentation
RMSA2Customer Inspired! Adapter with External RMS Threads and Internal M25 x 0.75 Threads
$24.35
Today
SM1A12 Support Documentation
SM1A12Adapter with External SM1 Threads and Internal M25 x 0.75 Threads
$21.86
Today
M25A1 Support Documentation
M25A1Adapter with External M26 x 0.706 Threads and Internal M25 x 0.75 Threads
$28.12
Today
M32A1 Support Documentation
M32A1Customer Inspired! Adapter with External M32 x 0.75 Threads and Internal M25 x 0.75 Threads
$24.35
Today
M32M25S Support Documentation
M32M25SCustomer Inspired! Brass Microscope Adapter with External M32 x 0.75 Threads and Internal M25 x 0.75 Threads
$21.22
Today
SM2A33 Support Documentation
SM2A33Adapter with External SM2 Threads and Internal M25 x 0.75 Threads
$27.59
7-10 Days
GCMA1 Support Documentation
GCMA1Adapter with External SM2 Threads and Internal M25 x 0.75 Threads, Ø35.0 mm Counterbore
$54.11
Today