Adjustable SM2 Lens Tubes

  • Rotating Adjustment of Ø2" Optics
  • Non-Rotating Adjustment of Ø1" Optics
  • Internal and External SM2 (2.035"-40) Threads


Non-Rotating Zoom Housing


SM2V10 Adjustable Lens Tube Connected to a Ø2" Lens Tube and Post-Mounted Using an SM2RC Slip Ring


Application Idea

Adjustable Lens Tubes


Adjustable Collimation Adapter

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  • Adjustable Positioning of Optics Along the Optical Axis within SM2 Lens Tube Systems
  • Internally and Externally SM2 (2.035" -40) Threaded
  • Rotating and Non-Rotating Optic Designs Available

Adjustable lens tubes allow for the adjustment of an optic's position along the optical axis within a lens tube system. Our adjustable lens tubes with extended external threads are designed to house a Ø2" optic and offer up to 1.31" (33.3 mm) of rotating optic travel. The SM2NR1 Zoom Housing provides 1.16" (29.5 mm) of non-rotating adjustment at 17 mm per revolution for a Ø1" optic; it can be mounted between two fixed lens tubes. The SM2F Adjustable Collimation Adapter provides 20 mm of non-telescoping, rotating adjustment of a Ø2" (Ø50 mm) collimation optic. 

Alternatives Ø1/2", Ø1", Ø1.5", and Ø3" Adjustable Lens Tubes Ø1" Non-Rotating Adjustable Focus Lens Tubes

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:
Mikael Malmström  (posted 2020-06-11 10:56:31.613)
How can I go from SM2F directly to SM3? I can not find an adapter from M62 to SM3... I want to be able to move a SM2 negative lens outside of the SM2F into a SM3 tube.
YLohia  (posted 2020-06-11 12:01:33.0)
Thank you for contacting Thorlabs. You may use the SM3A2 adapter to connect the SM2F to an SM3 tube. It features external SM2 threads and internal SM3 threads.

Ø2" Lens Tubes with Rotating Optic Adjustment

Adjustable Lens Tube Usage

Simplified Mechanical Drawing
  • Three Adjustment Ranges
    • SM2V05: 0.31" (7.9 mm)
    • SM2V10: 0.81" (20.6 mm)
    • SM2V15: 1.31" (33.3 mm)
  • Long Externally Threaded Section for Adjustable Positioning of Mounted Optics
  • Maximum Optic Thickness of 0.4" (10 mm) using Included SM2RR Retaining Ring

These SM2-threaded (2.035"-40) adjustable lens tubes have an extra-long externally threaded section, allowing Ø2" optics to be positioned along the optical axis of a Ø2" lens tube system. To operate, mount the optic in the internally threaded section using the included SM2RR retaining ring. Then thread the adjustable lens tube into a compatible (i.e., matching threads) lens tube or SM2-threaded lens mount until the optic is at the desired position. Use the included SM2NT locking ring to fix the position of the lens tube.

For applications where it is difficult to reach the locking ring by hand, we offer the SM2NT1 Slotted Locking Ring and SPW503 Spanner Wrench. This locking ring contains slots for the 2¼" end of the spanner wrench.

These adjustable lens tubes are an ideal solution for fine tuning of the first and last lenses in a lens tube system. Although a lens tube can be attached to the front of the adjustable lens tube, it should only be done after the position has been fixed, since this lens tube will need to be free to rotate and translate if the position is changed. Like our standard lens tubes, these adjustable lens tubes are made of black anodized aluminum.

Item # External Thread Length (L) Maximum Adjustment Rangea
SM2V05 0.5" (12.7 mm) 0.31" (7.9 mm)
SM2V10 1.0" (25.4 mm) 0.81" (20.6 mm)
SM2V15 1.5" (38.1 mm) 1.31" (33.3 mm)
  • Including one SM2NT locking ring and 0.08" (2 mm) minimum thread depth for the attached lens tube or component.
Alternatives Ø1/2", Ø1", Ø1.5", and Ø3" Adjustable Lens Tubes
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM2V05 Support Documentation
SM2V05Ø2" Adjustable Lens Tube, 0.31" Travel
SM2V10 Support Documentation
SM2V10Ø2" Adjustable Lens Tube, 0.81" Travel
SM2V15 Support Documentation
SM2V15Ø2" Adjustable Lens Tube, 1.31" Travel

Non-Rotating Zoom Housing for Ø1" Optics

SM2NR1 Zoom Housing Usage
Click to Enlarge

The SM2NR1 zoom housing can be mounted between two fixed SM2 lens tubes.
  • Adjustable Positioning of Ø1" Optics within SM2 Lens Tube Systems Without Rotation
  • 1.16" (29.5 mm) of Non-Rotating Adjustment at 17 mm Per Revolution
  • Mounts Ø1" Optics with Included SM1RR Retaining Ring
  • Internal and External SM2 (2.035"-40) Threads
  • Mounts Between Two Fixed SM2 Lens Tubes

Thorlabs' SM2NR1 provides 1.16" (29.5 mm) of non-rotating adjustment for Ø1" optics in a lens tube system. The SM2NR1 is SM2-threaded (2.035"-40) and can be mounted between two fixed lens tubes. It contains an internally SM1-threaded (1.035"-40) cell where optics are installed using the included SM1RR retaining ring. A double helical mechanism moves the optic back and forth while restricting any rotational movement.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM2NR1 Support Documentation
SM2NR1Ø2" Non-Rotating Zoom Housing for Ø1" Optics, 1.16" Travel

Adjustable Collimation Adapter for Ø2" or Ø50 mm Optics

LED Collimation Adapter
Click to Enlarge

The SM2F Installed on a M365LP1 Mounted LED with ACL50832U-B Condenser Lens
  • Translation of Ø2" or Ø50 mm Collimation Optic with 20 mm of Travel
  • External SM1 Threading (1.035"-40) at Input and Internal SM2 Threading (2.035"-40) at Output
  • Removable Threading Adapters at Input and Output; Remove the Input Adapter for SM2 Thread Compatibility at Both Ends
  • 10.0 mm (0.39") Thick Retaining Ring Ideal for Aspheric Lenses
  • Recommended for Collimating Mounted LEDs Using Condenser Lenses

This Adjustable Collimation Adapter provides 20 mm of non-telescoping, rotating translation for a Ø2" (Ø50 mm) optic with a clear aperture of Ø47.0 mm. As seen in the drawing to the right, the input and output apertures of the adapter are equipped with removable thread adapters. The input adapter is externally SM1 threaded (1.035"-40) and internally SM2 threaded (2.035"-40); removing it provides compatibility with SM2-threaded components. The output thread adapter is externally M62 x 0.75 threaded and internally SM2 threaded. We also offer versions with pre-mounted aspheric condensers here. The SM2F should be used at temperatures from 15 to 60 °C (non-condensing).

The inner carriage can be translated along the Z-axis by turning the adjustment ring (engraved with the Item # in the photos to the left) and locked into position by turning the locking screw on the side of the adjustment ring with a 2 mm (5/64") hex key. While the lens cell will rotate within the adapter housing when translated, the mounting threads on the housing remain fixed, allowing the SM2F to be mounted between fixed lens tubes. Lines with a 2 mm spacing are engraved on the housing as a rough guide for how far the carriage has been translated. Each collimation adapter also includes a 10-mm-thick, SM2-threaded retaining ring that allows an aspheric condenser lens to be mounted with our SPW604 Spanner Wrench.

Inserting or Removing Optics
To insert or remove an optic in these collimation adapters, use the adjustment ring to translate the inner carriage to the output end of the housing. Remove the included retaining ring using the SPW604 spanner wrench. If there is a lens installed already, remove it from the carriage. Insert another Ø2" or Ø50 mm optic into the carriage, and use the retaining ring to secure it.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SM2F Support Documentation
SM2FAdjustable Collimation Adapter for Ø2" or Ø50 mm Optic