Ø1.5" Lens Tubes

  • Lens Tubes Accept Ø1.5" (Ø38.1 mm) Optics
  • Compatible with All SM1.5-Threaded Components
  • Stackable Design Enables Construction of Multi-Element Optical Systems


0.3" Thread Depth


0.5" Thread Depth


1.00" Thread Depth


2.00" Thread Depth


SM1.5 (1.535"-40) Retaining Ring

Related Items

Please Wait
Lens Tube Engraving
Click to Enlarge

When an engraved lens tube is attached to another lens tube, the engraving of the connected end is no longer visible.
Additional Lens Tube Sizes
Ø30 mm
Adapters Button


  • Lens Tubes in Lengths from 0.30" (7.6 mm) to 2.00" (50.8 mm)
  • Tubes Directly Accept Ø1.5" (Ø38.1 mm) Optics

Lens tubes are ideal for creating compact optical subassemblies with light-tight beam paths. The Ø1.5" lens tubes sold here can be used to house one or several optical elements. Optics are separated and secured by retaining rings that are positioned at the desired depth within the lens tube using a spanner wrench. Each stackable lens tube ships with one retaining ring. Additional retaining rings can be purchased separately. In addition to the Ø1.5" lens tubes featured on this page, Thorlabs also offers versions from Ø1/2" to Ø3", each of which is equipped with an SM-series thread standard that depends on the tube diameter. Additional lens tube sizes can be found in the table to the right.

Lens Tube Compatible Products
Terminated Fiber
Fixed Fiber Collimator
Kinematic Fiber Collimator
LED Mounts LD Mounts Aspheric Lens Mounts Irises, Apertures, and Shutters Alignment Tools

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 2024-03-13 13:29:46.193)
Could slotted lens tubes like the ones available in 1" lens tube systems be made for 1.5" tube systems?
jdelia  (posted 2024-03-14 08:17:24.0)
Thank you for contacting Thorlabs. I have forwarded your request to our design engineers via our internal suggestion forum so that we may consider this as a catalog product line in the future.
user  (posted 2019-06-17 01:31:08.07)
Will you offer corresponding lens tube mounts (SM1.5 version of the SM1TC) and adapters to SM1 and 2?
llamb  (posted 2019-06-17 05:01:01.0)
Hello, thank you for contacting Thorlabs. We are indeed currently looking into offering thread adapters from SM1.5 to SM1 and SM2 threads. I have added your idea for SM1.5 lens tube mounts to our internal product forum as well. Thanks for the feedback!
Back to Top

Ø1.5" Stackable Lens Tubes

SM1.5Lxx Lens Tube Diagram
  • Stackable Design Enables Multi-Element Optical Systems
  • SM1.5-Threaded (1.535"-40) Bore Accepts Ø1.5" (Ø38.1 mm) Optics

These stackable Ø1.5" lens tubes provide a fast and easy means for building compact optical assemblies. They can directly interface with any SM1.5-threaded (1.535"-40) component to provide flexibility for complex optomechanical systems. One SM1.5RR Retaining Ring is included with each lens tube.

Item # L Internal Thread Depth
SM1.5L03 0.33" (8.4 mm) 0.30" (7.6 mm)
SM1.5L05 0.53" (13.5 mm) 0.50" (12.7 mm)
SM1.5L10 1.03" (26.2 mm) 1.00" (25.4 mm)
SM1.5L20 2.03" (51.6 mm) 2.00" (50.8 mm)

Alternatives Ø1/2", Ø1", Ø30 mm, Ø2", and Ø3" Stackable Lens Tubes
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM1.5L03 Support Documentation
SM1.5L03Customer Inspired! SM1.5 Lens Tube, 0.30" Thread Depth, One Retaining Ring Included
SM1.5L05 Support Documentation
SM1.5L05Customer Inspired! SM1.5 Lens Tube, 0.50" Thread Depth, One Retaining Ring Included
SM1.5L10 Support Documentation
SM1.5L10Customer Inspired! SM1.5 Lens Tube, 1.00" Thread Depth, One Retaining Ring Included
SM1.5L20 Support Documentation
SM1.5L20Customer Inspired! SM1.5 Lens Tube, 2.00" Thread Depth, One Retaining Ring Included
Back to Top

Ø1.5" Retaining Rings and Spanner Wrenches

  • SM1.5RR Retaining Rings Secure Ø1.5" (Ø38.1 mm) Optics
  • SPW608 Hollow Spanner Wrench Provides Unobstructed Beam Path During Adjustment
  • SPW801 Adjustable Spanner Wrench can Accommodate Diameters from 0.12" (3.0 mm) to 2.89" (73.4 mm)

These Retaining Rings can be used to secure optical components into our SM1.5-threaded (1.535"-40) lens tubes. One retaining ring is included with in the purchase of a lens tube; however, additional rings enable multiple optics to be secured inside the same lens tube. The SPW608 Spanner Wrench or the SPW801 Adjustable Spanner Wrench can be used to position SM1.5RR retaining rings. Please note that the SPW801 wrench can withstand a maximum torque of 80 lb-in. We also offer the SPB1.5 SM1.5 Spanner Bit, which can be used with a standard 1/4" hex driver (sold separately). 

Alternatives Ø1/2", Ø1", Ø2", and Ø3" Spanner Wrenches Ø1/2", Ø1", Ø2", and Ø3" Retaining Rings
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM1.5RR Support Documentation
SM1.5RRSM1.5 Retaining Ring for Ø1.5" Lens Tubes and Mounts
SPW608 Support Documentation
SPW608Customer Inspired! Spanner Wrench for SM1.5-Threaded Retaining Rings, Graduated Scale with 0.02" (0.5 mm) Increments, Length = 3.88"
SPW801 Support Documentation
SPW801Adjustable Spanner Wrench
SPW102 Support Documentation
SPW102Adjustable Spanner Wrench, Replacement Blade Set