Lens Tube Couplers and Locking Rings

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 the video above 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 table below lists the specifications for all available couplers and locking rings.

Item #	SM05T1	SM05T2	SM05T10	SM05T20	SM05NT	SM05NT1
Description	SM05 Lens Tube Coupler				SM05 Locking Ring	Slotted SM05 Locking Ring
Threads	Internal SM05	External SM05			Internal SM05
Length	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 Rangea	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

• 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.

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 the video above).

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.

The table below gives the specifications for all available couplers and locking rings.

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	0.35" (8.9 mm)	0.5" (12.7 mm)	1.0" (25.4 mm)	0.11" (2.8 mm)
Lens Tube Separation Rangea	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

• 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.

The SM1T1 is an internally SM1-threaded coupler for joining two externally threaded SM1 (1.035"-40) components. Its length of 0.28" is designed for direct mating of two standard lens tubes (SM1Lxx series). 

Thorlabs offers five externally threaded couplers for joining internally SM1-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 one ships with two SM1NT 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 SM1-threaded components. The use of multiple locking rings allows lens tubes to be locked independently, such as when using crossed polarizers (see the video above for a demonstration).

For applications where it is difficult to reach the locking ring by hand, we offer the SM1NT1 Slotted Locking Ring and SPW502 Spanner Wrench. This locking ring contains slots for the 1¼" end of the spanner wrench.

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.

The table below gives the specifications for all available couplers and locking rings. 

Item #	SM1T1	SM1T2	SM1T10	SM1T20	SM1T30	SM1T40	SM1NT	SM1NT1
Description	SM1 Lens Tube Coupler						SM1 Locking Ring	Slotted SM1 Locking Ring
Threads	Internal SM1	External SM1					Internal SM1	Internal SM1
Length	0.28" (7.1 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)	0.11" (2.8 mm)	0.11" (2.8 mm)
Lens Tube Separation Rangea	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)	0.22" - 2.84" (5.6 mm - 72.1 mm)	0.22" - 3.84" (5.6 mm - 97.5 mm)	N/A	N/A
Drawing

• 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.

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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
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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
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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).

The figure to the right 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. 

• 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.

• 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).

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SM1CMF Coupler Diagram

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Components Included with SM1CMF Bundle
(Lens Tubes and Post Sold Separately)

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

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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 photos to the right). 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.

Item #	SM1.5NT
Description	SM1.5 Locking Ring
Threads	Internal SM1.5
Length	0.11" (2.8 mm)
Drawing

The SM1.5T 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.

See the table to the right for specifications.

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 the video above 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.

The table below gives the specifications for all available couplers and locking rings.

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	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 Rangea	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

• 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.

Click to Enlarge
An SM2CPL10 holding two Ø2" lens tubes. A rubber gasket makes the coupler light tight.

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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 photos to the right). 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.

Click to Enlarge
SM3T1 used to Couple Two Externally-Threaded Ø3" Lens Tubes

Item #	SM3T1	SM3T2	SM3NT
Description	SM3 Lens Tube Coupler		SM3 Lock Nut
Threads	Internal SM3	External SM3	Internal SM3
Length	0.28" (7.1 mm)	0.5" (12.7 mm)	0.11" (2.8 mm)
Max Adjustment Rangea	N/A	0.22" - 0.34" (5.6 - 8.6 mm)	N/A
Drawing

• 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 the video above for a demonstration).

The table to the right gives the specifications for all available items.