Lens Tube Couplers and Locking Rings

Connect Two Lens Tubes Together
Threaded and Clamping Couplers Available
Locking Rings Create Mechanical Stop Along Threads
Options for SM05, SM1, SM1.5, SM2, SM3, and C-Mount Threading

SM2T1

Couples Two
Externally Threaded
SM2 Lens Tubes

CMT10

Couples Two
Internally Threaded
C-Mount Lens Tubes

SM1S10

Spacer for Two Internally Threaded SM1 Lens Tubes

SM1CPL

Shown Clamping Two
SM1 Lens Tubes

Application Idea

SM1CMM Shown Coupling Two KCB1 Kinematic Mirror Mounts

CMNT1

Slotted C-Mount
Locking Ring

Please Wait

Overview
Threading Specs
Feedback

Quick Links
SM05	Threaded Couplers and Locking Rings
C-Mount	Threaded Couplers and Locking Rings
C-Mount	Flexure Sleeve Couplers
SM1	Threaded Couplers and Locking Rings
	Spacer without Internal Threads
	Non-Rotating Couplers
	Flexure Sleeve Couplers
SM1.5	Locking Rings
SM2	Threaded Couplers and Locking Rings
SM2	Flexure Sleeve Couplers
SM3	Threaded Couplers and Locking Ring

Thorlabs' Lens Tube Couplers are available with internal threading, external threading, or clamping designs, making it possible to couple our SM05, SM1, SM2, or SM3 Lens Tubes, as well as our C-Mount Extension Tubes. Our threaded lens tube couplers are designed to couple two components with external threads or two components with internal threads. Locking rings for securing externally SM05-, SM1-, SM1.5-, SM2-, SM3-, and C-mount threaded parts are available as well.

Our Non-Rotating Couplers for SM1 Lens Tubes are ideal for mounting SM1-threaded components that are sensitive to rotation, such as wired components or lens tubes with polarization optics. Coupling adapters are threaded onto the lens tubes and then clamped together, allowing components to be joined without rotating the component. These light-tight couplers are also ideal for bridging existing lens tube systems.

The Flexure Sleeve Couplers allow lens tubes to be locked independently. The flexure clamping mechanism allows lens tubes to be positioned with either external or internal threads facing outward. These couplers feature a light-tight design. The SM1CPL Flexure Sleeve Couplers hold SM1 lens tubes and C-Mount extension tubes while the SM2CPL Flexure Sleeve Couplers hold SM2 lens tubes.

Video 1.1 Externally threaded lens tube couplers can be used to create assemblies that require optics to be mounted in specific orientations. When the orientation is adjusted, the tube length also changes. Here, the threaded coupler is used to build a setup that incorporates crossed polarizers. Note that the white line on each polarizer housing indicates the transmission axis. For applications sensitive to distance as well as orientation, please see our Non-Rotating Couplers below.

Click to Enlarge

View Imperial Product List

Item #	Qty	Description
Imperial Product List
SM1T20	1	SM1 (1.035"-40) Coupler, External Threads, 2" Long, Two Locking Rings
CP33	1	SM1-Threaded 30 mm Cage Plate, 0.35" Thick, 2 Retaining Rings, 8-32 Tap
CP02F	1	SM1-Threaded 30 mm Flexure Cage Plate, 0.35" Thick, 2 Retaining Rings, Imperial
ER2-P4	1	Cage Assembly Rod, 2" Long, Ø6 mm, 4 Pack
ER3-P4	1	Cage Assembly Rod, 3" Long, Ø6 mm, 4 Pack
C4W	1	30 mm Cage Cube
CCM1-M01	1	30 mm Cage Cube-Mounted Protected Gold Turning Mirror, 8-32 Tap

View Metric Product List

Item #	Qty	Description
Metric Product List
SM1T20	1	SM1 (1.035"-40) Coupler, External Threads, 2" Long, Two Locking Rings
CP33/M	1	SM1-Threaded 30 mm Cage Plate, 0.35" Thick, 2 Retaining Rings, M4 Tap
CP02F/M	1	SM1-Threaded 30 mm Flexure Cage Plate, 0.35" Thick, 2 Retaining Rings, Metric
ER2-P4	1	Cage Assembly Rod, 2" Long, Ø6 mm, 4 Pack
ER3-P4	1	Cage Assembly Rod, 3" Long, Ø6 mm, 4 Pack
C4W	1	30 mm Cage Cube
CCM1-M01/M	1	30 mm Cage Cube-Mounted Protected Gold Turning Mirror, M4 Tap

Figure 1.2 The SM1T20 Lens Tube Coupler can be used to join sliding 30 mm cage system segments. In the photo, the locking rings on the SM1T20 Coupler are tightened to retain the rotational alignment of the two cage segments. The cage rod flexure screws on the CP02F Cage Plate must be loosened to allow the cage segment on the right to slide.

Click to Enlarge
Figure 1.3 Slotted locking rings can be tightened using the SPW502, SPW503, or SPW504 wrenches.

Click to Enlarge

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 Grades^a
Minor Diameter	Internal	4, 5, 6, 7, 8
Major Diameter	External	4, 6, 8
Pitch Diameter	Internal	4, 5, 6, 7, 8
Pitch Diameter	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:

Katsuya Nozawa (posted 2025-05-09 14:21:11.247)

Dear Sir, I am using your SM1CH, SM1CF and SM1A39 to change C-mount cameras on a microscope, such as from a visible camera to an InGaAs camera. It is much better than using C-mount threads directly, because I don't have to rotate a camera and I can fix the camera on desired angle. I hope you will make Non-Rotating Coupling Adapters with external C-mount threads.

jpoling (posted 2025-05-09 07:06:58.0)

Thank you for your valuable feedback and for the description of your application with our products. I have posted this suggestion to our engineering forums so that we can look into the possibility of offering a non-rotating coupling adapter with external C-mount threads in the future.

Michael Molter (posted 2023-03-10 14:51:55.26)

Is there a reason the OD of this flange doesn't adhere to the KF-25 standard of 1.57"? Per the model, It's a little smaller than anticipated. I assume it will still seal okay on a KF-25 fitting/clamp?

ksosnowski (posted 2023-03-24 05:36:20.0)

Hello Michael, thanks for reaching out to Thorlabs. This flange in particular is not intended to be vacuum compatible as it is anodized, but is designed to be light-tight. This extra clearance allows the SM1CF to fit inside of other 1.5" clamp equipment as well. In our design and prototyping we found this to give reliable mating across other supplier's KF-25 fittings, while preventing lateral shift of either lens tube section due to mating differences in systems. This does not interfere with the seal, and should present no issues in purging applications. I have reached out directly to discuss this further.

Eric Lentz (posted 2022-06-06 11:17:24.29)

Hello. It would be great to have a part number etched on this so we can order more and know what it is in the future. Thanks

jdelia (posted 2022-06-06 02:12:18.0)

Thank you for contacting Thorlabs, and for providing this valuable feedback. We will be forwarding your request over to our engineers through our internal suggestion forum.

伟林何 (posted 2019-12-11 08:51:41.717)

"CMNT - C-Mount(1.00英寸-32)锁定环，1.25英寸外径"这个是2.8mm厚的，有没有更薄的，比如2mm及以下的？

llamb (posted 2019-12-12 03:16:55.0)

Thank you for your feedback. We can indeed offer custom, thinner versions of the CMNT locking ring. We have reached out to you directly to discuss potential quoting. 感谢您的反馈意见。我们确实可以提供定制的，更薄版本的CMNT锁紧环。我们已直接与您联系，讨论潜在的报价。

user (posted 2014-10-13 16:41:59.227)

On SM05 and SM1 couplers, can I confirm, as suggested by the Autocad PDF files, that two retaining rings are supplied and so aren't required as an additional order i.e. SM05T2 is sufficient for mounting two tubes and locking them in place?

cdaly (posted 2014-10-13 02:14:55.0)

Response from Chris at Thorlabs: The internally threaded SM05T1 and SM1T1 couplers do not come with retaining rings. The externally threaded SM05T2 and SM1T2 couplers do both come with the two locking nuts shown. SM05T2 can be used to mount together two internally threaded ends of lens tubes, locking them in place with the provided nuts.

steve (posted 2013-06-04 00:01:55.8)

How about an electrical isolating version (external and/or internal threads). For example, many laser diodes have their case electrically live and thus when mounted to your tubes, the whole tube assembly and whatever is connects to becomes connected. Especially an issue if you also mount a bare photodiode into a tube wince photodiodes also often have their case electrically active. I see you make Delrin adaptors for thermal isolation.

tcohen (posted 2013-06-06 12:45:00.0)

Response from Tim at Thorlabs: Thank you for your suggestion. The anodization process used on the majority of our optomech makes them fairly electrically isolated.

tcohen (posted 2012-07-19 10:56:00.0)

Response from Tim at Thorlabs: Thank you very much for your feedback! This can be done with lens tubes and the adapters on this page, but I agree that this would be a much more convenient solution. Our design team will look at this. ~1/3 of our products are customer inspired, including the original versions of these. Thank you for sharing your feedback so that we can continue to increase our selection with products directly relevant to your applications.

nkad (posted 2012-07-17 15:29:53.0)

A much longer range of externally threaded SM1 coupling tubes would be really helpful, this would allow for a huge range of adjustment between enclosed optics. I would suggest 4" and 6".

acable (posted 2007-12-12 10:14:08.0)

It would be really helpful to have photos for each of the individual parts shown on this page.

SM05 Lens Tube Couplers

Zoom

The SM05T1 is an internally threaded coupler for joining two externally threaded SM05 (0.535"-40) components. It is designed to directly mate two of our SM05-threaded standard lens tubes.

Thorlabs offers three externally threaded couplers for joining internally SM05-threaded components. These feature external threads along the entire length of the part, allowing for optimization of the position and angle of the attached components. Each coupler ships with two SM05NT locking rings, which can be tightened by hand to secure the attached components. Additional locking rings can be purchased separately to limit the external thread depth of any SM05-threaded components. The use of multiple locking rings allows lens tubes to be locked independently, such as when using crossed polarizers (see Video 1.1 for a demonstration).

For applications where it is difficult to reach the locking ring by hand, we offer the SM05NT1 Slotted Locking Ring and SPW502 Spanner Wrench. This locking ring contains slots for the 3/4" end of the spanner wrench. The SM05NT1V locking ring is a vacuum-compatible version of the SM05NT1 locking ring. Made from 6061-T6 aluminum, this unanodized locking ring is vacuum compatible down to 10^-6 Torr.

Table G1.1 lists the specifications for all available couplers and locking rings.

Table G1.1 Specifications
Item #	SM05T1	SM05T2	SM05T10	SM05T20	SM05NT	SM05NT1	SM05NT1V
Description	SM05 Lens Tube Coupler				SM05 Locking Ring	Slotted SM05 Locking Ring	Vacuum-Compatible Slotted SM05 Locking Ring
Threads	Internal SM05	External SM05			Internal SM05
Length^a	0.28" (7.1 mm)	0.5" (12.7 mm)	1.0" (25.4 mm)	2.0" (50.8 mm)	0.11" (2.8 mm)
Lens Tube Separation Range^b	N/A	0.22" - 0.34" (5.6 mm - 8.6 mm)	0.22" - 0.84" (5.6 mm - 21.3 mm)	0.22" - 1.84" (5.6 mm - 46.7 mm)	N/A
Drawing

Couplers of custom lengths can be ordered by contacting Tech Support.
The minimum is based on the sum of the thickness of two SM05NT locking rings (or equivalently two SM05NT1 locking rings), and the maximum is based on the length of the tube minus a 0.08" (2 mm) minimum thread depth for both attached components.

C-Mount Extension Tube Couplers

Zoom

The CMT1 is an internally C-Mount-threaded coupler for joining two externally threaded C-Mount (1.00"-32) components. Its length of 0.35" is designed for direct mating of two C-Mount Extension Tubes.

The CMT2 and CMT10 externally threaded couplers are designed for joining internally C-Mount-threaded components. These feature external threads along the entire length of the part, allowing the relative position and rotation of a camera and lens to be adjusted. Each coupler ships with two CMNT Locking Rings, which can be tightened by hand to secure the attached components. Additional locking rings can be purchased separately to limit the external thread depth of any C-Mount-threaded components. The use of multiple locking rings allows lens tubes to be locked independently, such as when using crossed polarizers (see Video 1.1 for a demonstration).

For applications where it is difficult to reach the locking ring by hand, we offer the CMNT1 Slotted Locking Ring and SPW502 Spanner Wrench. This locking ring contains slots for the 1¼" end of the spanner wrench.

Table G2.1 gives the specifications for all available couplers and locking rings.

Table G2.1 Specifications
Item #	CMT1	CMT2	CMT10	CMNT	CMNT1
Description	C-Mount Extension Tube Coupler			C-Mount Locking Ring	C-Mount Slotted Locking Ring
Threads	Internal C-Mount	External C-Mount		Internal C-Mount
Length^a	0.35" (8.9 mm)	0.5" (12.7 mm)	1.0" (25.4 mm)	0.11" (2.8 mm)
Lens Tube Separation Range^b	N/A	0.22" - 0.34" (5.6 mm - 8.6 mm)	0.22" - 0.84" (5.6 mm - 21.3 mm)	N/A	N/A
Drawing

Couplers of custom lengths can be ordered by contacting Tech Support.
The minimum is based on the sum of the thickness of two CMNT locking rings (or equivalently two CMNT1 locking rings), and the maximum is based on the length of the tube minus a 0.08" (2 mm) minimum thread depth for both attached components.

SM1 Lens Tube Couplers

Zoom

The SM1T1 0.28" Long, Internally SM1-Threaded (1.035"-40) Coupler is designed to mate two lens tubes with external SM1 threads end-to-end.

The SM1T3 0.25" Long, Externally SM-Threaded Coupler is designed to mate two lens tubes with internal SM1-threads end-to-end.

Thorlabs offers six externally threaded couplers with locking rings for joining internally SM1-threaded components. These couplers feature external threads allowing for optimization of the position and angle of the attached components. The SM1T4 0.47" long coupler has external threading on both ends and a fixed shoulder 0.12" from one side; one SM1NT1 locking ring is also included. The other couplers have external threading over their entire length and ship with two SM1NT locking rings. Locking rings can be tightened by hand to secure the attached components. Additional locking rings can be purchased separately to limit the external thread depth of any SM1-threaded components. The use of multiple locking rings allows lens tubes to be locked independently, such as when using crossed polarizers (see Video 1.1 for a demonstration).

For applications where it is difficult to reach the locking ring by hand, the 1¼" end of the SPW502 spanner wrench can engage with the slots in the SM1NT1 locking ring or the fixed shoulder on the SM1T4 lens tube coupler. The SM1NT1 locking ring is also available separately and can be used to replace the SM1NT locking rings included with some couplers. The SM1NT1V locking ring is a vacuum-compatible version of the SM1NT1 locking ring. Made from 6061-T6 aluminum, this unanodized locking ring is vacuum compatible down to 10^-6 Torr.

For a one-component solution for spacing two externally threaded SM1 components at a fixed distance, please see our line of lens tubes without external threads, available in lengths ranging from 0.5" to 3.5". For a one-component solution for spacing internally threaded SM1 components at a fixed distance, see our selection of SM1 Lens Tube Spacers below.

Tables G3.1 and G3.2 give the specifications for all available couplers and locking rings.

Table G3.1 Coupler Specifications
Item #	SM1T1	SM1T3	SM1T4	SM1T2	SM1T10	SM1T20	SM1T30	SM1T40
Description	SM1 Lens Tube Coupler		SM1 Lens Tube Coupler with Fixed Shoulder	SM1 Lens Tube Coupler
Threads	Internal SM1	External SM1
Included Locking Rings	N/A		SM1NT1 Locking Ring	Two SM1NT Locking Rings
Length^a	0.28" (7.1 mm)	0.25" (6.4 mm)	0.47" (11.9 mm)	0.5" (12.7 mm)	1.0" (25.4 mm)	2.0" (50.8 mm)	3.0" (76.2 mm)	4.0" (101.6 mm)
Lens Tube Separation Range^b	N/A		0.22" - 0.27"^b (5.6 mm - 6.8 mm)	0.22" - 0.34"^c (5.6 mm - 8.6 mm)	0.22" - 0.84"^c (5.6 mm - 21.3 mm)	0.22" - 1.84"^c (5.6 mm - 46.7 mm)	0.22" - 2.84"^c (5.6 mm - 72.1 mm)	0.22" - 3.84"^c (5.6 mm - 97.5 mm)
Drawing

Couplers of custom lengths can be ordered by contacting Tech Support.
The minimum is based on the sum of the thickness of the SM1NT1 locking ring and the fixed shoulder, and the maximum is based on the length of the tube minus the distance to the fixed shoulder and a 0.08" (2 mm) minimum thread depth for an attached component on the opposite end.
The minimum is based on the sum of the thickness of two SM1NT locking rings (or equivalently two SM1NT1 locking rings), and the maximum is based on the length of the tube minus a 0.08" (2 mm) minimum thread depth for both attached components.

Table G3.2 Locking Ring Specifications
Item #	SM1NT	SM1NT1	SM1NT1V
Description	SM1 Locking Ring	Slotted SM1 Locking Ring	Vacuum-Compatible Slotted SM1 Locking Ring
Threads	Internal SM1
Length^a	0.11" (2.8 mm)
Drawing

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+1 Qty Docs Part Number - Universal Price Available

SM1T1 SM1 (1.035"-40) Coupler, Internal Threads

$11.86

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SM1T3 SM1 (1.035"-40) Coupler, External Threads, 0.25" Long

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SM1T4 SM1 (1.035"-40) Coupler, External Threads, Fixed Shoulder and Locking Ring

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SM1T2 SM1 (1.035"-40) Coupler, External Threads, 0.5" Long, Two Locking Rings

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SM1T10 Customer Inspired! SM1 (1.035"-40) Coupler, External Threads, 1" Long, Two Locking Rings

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SM1T20 Customer Inspired! SM1 (1.035"-40) Coupler, External Threads, 2" Long, Two Locking Rings

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SM1T30 SM1 (1.035"-40) Coupler, External Threads, 3" Long, Two Locking Rings

$36.56

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SM1T40 Customer Inspired! SM1 (1.035"-40) Coupler, External Threads, 4" Long, Two Locking Rings

$44.18

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SM1NT SM1 (1.035"-40) Locking Ring, 1.25" Outer Diameter

$8.12

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SM1NT1 SM1 (1.035"-40) Locking Ring, 1.25" Outer Diameter, Slots for Spanner Wrench

$11.95

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SM1NT1V Vacuum-Compatible SM1-Threaded Locking Ring, 1.25" Outer Diameter, Slots for Spanner Wrench

$13.05

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SM1 Lens Tubes Without Internal Threads

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View Imperial Product List

Item #	Qty	Description
Imperial Product List
PH4	1	Ø1/2" Post Holder, Spring-Loaded Hex-Locking Thumbscrew, L = 4"
SM1S30	1	SM1 Lens Tube Spacer, 3" Long
SM1L30C	2	SM1 Slotted Lens Tube, 3" Thread Depth, 2 Retaining Rings Included
TR3	1	Ø1/2" Optical Post, SS, 8-32 Setscrew, 1/4"-20 Tap, L = 3"
SM1RC	1	Slip Ring for SM1 Lens Tubes and C-Mount Extension Tubes, 8-32 Tap

View Metric Product List

Item #	Qty	Description
Metric Product List
SM1S30	1	SM1 Lens Tube Spacer, 3" Long
SM1L30C	2	SM1 Slotted Lens Tube, 3" Thread Depth, 2 Retaining Rings Included
PH100/M	1	Ø12.7 mm Post Holder, Spring-Loaded Hex-Locking Thumbscrew, L=100 mm
SM1RC/M	1	Slip Ring for SM1 Lens Tubes and C-Mount Extension Tubes, M4 Tap
TR75/M	1	Ø12.7 mm Optical Post, SS, M4 Setscrew, M6 Tap, L = 75 mm

Figure G4.1 SM1S30 Lens Tube Spacer Used to Separate Two SM1L30C
Slotted Lens Tubes

Use as Spacers Between Lens Tubes
External SM1 Threading on Each End
Six Lengths Ranging from 1.0" (25.4 mm) to 3.5" (88.9 mm)

These externally threaded Lens Tube Spacers are designed to connect two components with internal SM1 threads at a fixed distance. They are internally unthreaded and have a clear aperture of Ø0.95" (Ø24.0 mm).

Figure G4.1 shows two SM1L30C slotted lens tubes holding two plano-convex lenses. Separating these is the SM1S30 lens tube spacer, attached to a post with an SM1RC lens tube slip ring. Lens tube spacers allow significant space to be added between two fixed lenses using only one component.

SM1 Lens Tubes Without External Threads

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Allows Coupling of Two Externally SM1-Threaded Components
Use with Lens Tube Couplers to Stack Multiple Lens Tubes
Seven Lengths Ranging from 1/2" (12.7 mm) to 3.5" (88.9 mm)

These internally threaded Lens Tubes are designed to connect two components with external SM1 threads. Alternatively, optics can be housed inside with access to both ends. To join these lens tubes end-to-end, use an SM1 Lens Tube Coupler, sold above. Two SM1RR Retaining Rings are included with each lens tube.

Alternatives	Ø1/2" and Ø2" Lens Tubes Without External Threads

Based on your currency / country selection, your order will ship from Newton, New Jersey

+1 Qty Docs Part Number - Universal Price Available

SM1M05 Customer Inspired! SM1 Lens Tube Without External Threads, 1/2" Long, Two Retaining Rings Included

$16.44

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SM1M10 Customer Inspired! SM1 Lens Tube Without External Threads, 1" Long, Two Retaining Rings Included

$18.15

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SM1M15 SM1 Lens Tube Without External Threads, 1.5" Long, Two Retaining Rings Included

$21.23

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SM1M20 Customer Inspired! SM1 Lens Tube Without External Threads, 2" Long, Two Retaining Rings Included

$21.23

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SM1M25 SM1 Lens Tube Without External Threads, 2.5" Long, Two Retaining Rings Included

$22.82

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SM1M30 Customer Inspired! SM1 Lens Tube Without External Threads, 3" Long, Two Retaining Rings Included

$22.82

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SM1M35 SM1 Lens Tube Without External Threads, 3.5" Long, Two Retaining Rings Included

$36.70

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SM1 Non-Rotating Lens Tube Couplers

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Bundle Contents
Item #	Adapters	Coupler
SM1CFF	Two Internal SM1 Adapters (SM1CF)	Clamp and Centering Ring (SM1CH)
SM1CMF	Internal SM1 Adapter (SM1CF)
SM1CMF	External SM1 Adapter (SM1CM)
SM1CMM	Two External SM1 Adapters (SM1CM)

Non-Rotating, Light-Tight Coupler Connects SM1 Lens Tubes
Clamp Housing Binds Separate SM1-Threaded Assemblies Together
Clamp and Thread Mating Adapters Available in Bundles or as Separate Components
Compatible with KF25 Vacuum Hardware*
#8 (M4) Counterbore for use with Ø1/2" Posts

Thorlabs' Non-Rotating SM1 Lens Tube Couplers enable SM1-threaded (1.035"-40) lens tubes or components to be joined without rotating the component to engage the SM1 thread. This allows SM1 lens tube systems to be mated without changing the orientation, which is critical in polarization applications. These couplers also allow SM1-threaded components, such as our power meter sensors or other SM1-threaded detectors, to be attached to a system without coiling the sensor cable.

To join two SM1-threaded components together, an adapter with internal or external threads is attached to each part. An aluminum centering ring with a Viton^® O-Ring is inserted between the adapters and the parts are pressed together. The clamp housing is then engaged using a 5/64" (2.0 mm) hex key, which compresses the adapters and O-ring together, creating a light-tight and airtight seal. The clamp housing offers a #8 (M4) counterbore for mounting to our Ø1/2" Posts.

*Due to the outgassing of anodized aluminum, this coupler is not suitable for vacuum applications. Only the coupling adapters are compatible with KF25 centering rings and clamping hardware. For purging applications, positive pressure can be maintained up to 50 psi (3.4 bar).

Click for Details
Figure G6.1 SM1CMF Coupler Diagram

Click for Details
Figure G6.2 Components Included with SM1CMF Bundle (Lens Tubes and Post Sold Separately)

Video G6.3 SM1CMF Installation

SM1 Lens Tube Flexure Sleeve Couplers

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Figure G7.2 SM1CPL Holding Two Ø1" Lens Tubes. A rubber gasket makes the coupler light tight.

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Figure G7.1 Lens Tubes Are Secured by Tightening Two 5/64" Hex Screws

Flexure Design Holds SM1 Lens Tubes, C-Mount Extension Tubes, or Other Ø1.2" Outer Diameter Cylindrical Objects
Available in Three Lengths: 0.5", 1.0", and 3.0"
RTV103 Black Silicone Gasket Provides Light-Tight Coupling
Lens Tubes can be Positioned Along the Entire Length, Facing Either Direction

These Lens Tube Couplers are flexure-clamping sleeves that can hold any Ø1" lens tube, C-Mount extension tube, or other Ø1.2" outer diameter cylindrical object. A lens tube can be slid into each end of the coupler and secured by tightening the two 5/64" (2 mm) hex screws on the side of the sleeve.

Each coupler features a black silicone gasket along the clamping section to provide light-tight coupling of lens tubes (see Figures G7.1 and G7.2). Lens tubes can be mounted with either internal or external threads facing out and at any position along the length of the coupler as long as there are at least 6 mm of the tube inside the clamp.

SM1.5 Locking Rings

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Table G8.1 Specifications
Item #	SM1.5NT	SM1.5NT1
Description	SM1.5 Locking Ring	SM1.5 Slotted Locking Ring
Threads	Internal SM1.5
Length	0.11" (2.8 mm)
Drawing

The SM1.5NT Locking Ring has internal SM1.5 (1.535"-40) threads and a knurled outer edge. It can be used to limit the external thread depth of any SM1.5-threaded components such, as the KAD1F kinematic adapter. The use of two locking rings allows lens tubes to be locked in independent rotational orientations on both ends of an SM1.5-threaded component. Alternatively, a pair of locking rings screwed against each other may be used to create a hard stop.

For applications where it is difficult to reach the locking ring by hand, we offer the SM1.5NT1 Slotted Locking Ring and SPW504 Spanner Wrench. This locking ring contains slots for the 2¼" end of the spanner wrench.

See Table G8.1 for specifications.

SM2 Lens Tube Couplers

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The SM2T1 is an internally threaded coupler for joining two externally threaded SM2 (2.035"-40) components. It is designed to directly mate two of our SM2-threaded standard lens tubes.

Thorlabs offers three externally threaded couplers for joining internally SM2-threaded components. These feature external threads along the entire length of the part, allowing for optimization of the position and angle of the attached components. Each coupler ships with two SM2NT locking rings, which can be tightened by hand to secure the attached components. Additional locking rings can be purchased separately to limit the external thread depth of any SM2-threaded components. The use of multiple locking rings allows lens tubes to be locked independently, such as when using crossed polarizers (see Video 1.1 for a demonstration).

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.

Table G9.1 gives the specifications for all available couplers and locking rings.

Table G9.1 Specifications
Item #	SM2T1	SM2T2	SM2T10	SM2T20	SM2NT	SM2NT1
Description	SM2 Lens Tube Coupler				SM2 Locking Ring	SM2 Slotted Locking Ring
Threads	Internal SM2	External SM2			Internal SM2
Length^a	0.26" (6.6 mm)	0.5" (12.7 mm)	1.0" (25.4 mm)	2.0" (50.8 mm)	0.11" (2.8 mm)
Max Adjustment Range^b	N/A	0.22" - 0.34" (5.6 mm - 8.6 mm)	0.22" - 0.84" (5.6 mm - 21.3 mm)	0.22" - 1.84" (5.6 mm - 46.7 mm)	N/A
Drawing

Couplers of custom lengths can be ordered by contacting Tech Support.
The minimum is based on the sum of the thickness of two SM2NT locking rings (or equivalently two SM2NT1 locking rings), and the maximum is based on the length of the tube minus a 0.08" (2 mm) minimum thread depth for both attached components.

SM2 Lens Tube Flexure Sleeve Couplers

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Figure G10.2 An SM2CPL10 holding two Ø2" lens tubes. A rubber gasket makes the coupler light tight.

Click to Enlarge
Figure G10.1 Lens Tubes Are Secured by Tightening Two 5/64" Hex Screws

Flexure Design Holds SM2 Lens Tubes or Other Ø2.2" Outer Diameter Cylindrical Objects
Gasket Provides Light-Tight Coupling
Lengths of 0.5" or 1.0"
Lens Tubes can be Positioned Along the Entire Length, Facing Either Direction

These Lens Tube Couplers are flexure-clamping sleeves that can hold any Ø2" lens tube or other Ø2.2" outer diameter cylindrical object. A lens tube can be slid into each end of the coupler and secured by tightening the two 5/64" (2 mm) hex screws on the side of the sleeve.

Each coupler features a black silicone gasket along the clamping section to provide light-tight coupling of lens tubes (see Figures G10.1 and G10.2). The coupled lens tubes may be clamped with either the internal or external threads facing out and any position along the length of the coupler as long as there are at least 6 mm of the tube inside the clamp.

SM3 Lens Tube Couplers

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Figure 11.2 SM3T1 used to Couple Two Externally-Threaded Ø3" Lens Tubes

Table G11.1 Specifications
Item #	SM3T1	SM3T2	SM3NT
Description	SM3 Lens Tube Coupler		SM3 Lock Nut
Threads	Internal SM3	External SM3	Internal SM3
Length^a	0.28" (7.1 mm)	0.5" (12.7 mm)	0.11" (2.8 mm)
Max Adjustment Range^b	N/A	0.22" - 0.34" (5.6 - 8.6 mm)	N/A
Drawing

Couplers of custom lengths can be ordered by contacting Tech Support.
Including two SM3NT locking rings (or equivalently two SM3NT1 locking rings) and 0.08" (2 mm) minimum thread depth for both
attached components.

The SM3T1 is an internally threaded coupler for joining two externally threaded SM3 (3.035"-40) components. It is designed to directly mate two of our SM3-threaded standard lens tubes.

The SM3T2 Coupler features external SM3 threading (3.035"-40), which enables the coupling of two components with internal SM3 threads. It ships with two SM3NT locking rings, which can be used to lock the position of an attached SM3 component.

Additional locking rings (Item # SM3NT) can be purchased separately to limit the external thread depth of any SM3-threaded components. The use of multiple locking rings is particularly desirable in situations where you have two components with preferential relative directions, such as when using crossed polarizers (see Video 1.1 for a demonstration).

Table G11.1 gives the specifications for all available items.