Vacuum-Compatible Fixed Lens Mounts

  • Fixed Mounts for Ø1/2", Ø1", and Ø2" Optics
  • 8-32 (M4) Vented Tap for Post Mounting
  • Vacuum-Compatible to >10-6 Torr


For Ø1" Optics


For Ø2" Optics


For Ø1/2" Optics,
Back View

Application Idea

Build a vacuum-compatible optical assembly by mounting these fixed lens mounts to our vacuum-compatible Ø1/2" post system.

Related Items

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Double Vacuum Bag
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This cross-sectional view of a post-mounted LMRV1 shows how the vent hole at the rear of the mount prevents air from being trapped behind the mounting screw.

Additional Vacuum-Compatible Components

Many of our other optomechanical components can be special ordered for vacuum use. Contact for details.


  • Internal SM Threading with Retention Lip, One Retaining Ring Included
  • Ø1/2", Ø1", and Ø2" Versions Available
  • Unanodized 6061-T6 Aluminum
  • Vented Mounting Hole to Avoid Virtual Leaks
  • All Components Compatible with >10-6 Torr Environments Directly Out of the Packaging
  • All Components are Shipped Double Vacuum-Bagged for Cleanroom Use

Thorlabs offers vacuum-compatible versions of our standard fixed lens mounts for Ø1/2", Ø1", and Ø2" optics. Optics are secured against a retention lip at the back of the mount with the included retaining ring, threaded to our SM standard; see the Threading Specs tab to learn more about SM threading. These mounts are fabricated from unanodized 6061-T6 aluminum and double vacuum-bagged making them suitable for cleanroom and vacuum chamber applications. An 8-32 (M4) tapped mounting hole at the bottom of each mount is vented through the back of the body. Venting this tapped hole prevents air from becoming trapped behind the screw and causing virtual leaks in a vacuum system.

These vacuum-compatible fixed lens mounts can have their lens cells extended with vacuum-compatible lens tubes. Lens mounts can be used with our vacuum-compatible Ø1/2" post systems to build free-space optical assemblies within a vacuum chamber. Such assemblies can be fastened to unanodized aluminum breadboards, which are also vacuum compatible to 10-6 Torr when properly cleaned by the user. When building assemblies for vacuum systems, remember to use vented screws to prevent trapping air in blind threaded holes.

Vacuum Compatibility Information
Our vacuum-compatible optomechanics are chemically cleaned and prepared for vacuum applications before packaging. They are compatible directly out of the packaging with vacuum environments down to 10-6 Torr. With additional cleaning and processing, they can be used at even lower pressures, only limited by the outgassing rate of the aluminum (see the table below). The material properties of the aluminum and the cleaning methods completed by the end user should be used to determine the appropriateness of these products and materials in a specific vacuum system.

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:
Nick M  (posted 2020-08-27 10:55:22.167)
The LMR1V lens mount is easily the worst Thorlabs product I've used during my career. The retaining ring grinds against the internal threading to such a degree that it's liable to get stuck. Indeed, one of them was shipped to us with a stuck retaining ring. Even if the retaining ring doesn't get stuck, the act of tightening or loosening it will probably cover your optic in a fine dust of aluminium. How this passed QA is beyond me.
llamb  (posted 2020-09-18 03:45:26.0)
Thank you for contacting Thorlabs, and I'm very sorry to hear about your experience with the LMR1V. These parts are acid-etched and wiped down with alcohol and lint-free wipes during the manufacturing/assembly process. If you are seeing more dust or sticking, additional wiping with alochol/isopropanol could help alleviate that. In case you received faulty items, I have also reached out to you directly by email to troubleshoot further and help rectify the situation.

Vacuum-Compatible Fixed Lens Mounts

Vacuum Specifications
Vacuum Compatibility
as Packageda
>10-6 Torr
Materials 6061-T6 Aluminum
Preparation and
Chemically Cleaned and
Double Vacuum-Bagged
Aluminum Outgassing
Rate at 20 °C
7.6 x 10-9 Torr-Liters/s/cm2
  • This is the pressure at which these components can be used with no additional processing. They can be used at even lower pressures with additional cleaning and processing.
Vents Found on Back of Vacuum Compatible Fixed Optic Mounts
Click to Enlarge
The back of each mount features a vent for the tapped mounting holes.
  • Mount Ø1/2", Ø1", or Ø2" Optics
  • Internally SM Treaded with Retention Lip
  • Low Outgassing
  • Included Retaining Ring

These fixed optic mounts feature internal threading and a retention lip. The optic diameter and maximum thickness for each mount is given below. This thickness takes into account the depth required for the retaining ring to fully engage its threads to secure the optic against the retention lip. The retaining ring can be adjusted with any of the suggested spanner wrenches listed below.

The body of the mount features a vent hole, allowing for air trapped under the set screw to easily escape. Do not plug this vent hole or attempt to use it as a mounting point.

Item # Optic
Max Optic
Clear Apertureb Optical Height Replacement Retaining Ring Suggested
Spanner Wrench
LMR05V(/M) Ø1/2" 0.21" (5.0 mm) Ø0.44" (Ø11.0 mm) 0.63" (16.0 mm) SM05RRV SPW603, SPW603L, or SPW801
LMR1V(/M) Ø1" 0.28" (7.1 mm) Ø0.90" (Ø23.0 mm) 0.87" (22.1 mm) SM1RRV SPW602, SPW606 or SPW801
LMR2V(/M) Ø2" 0.36" (9.2 mm) Ø1.90" (Ø48.5 mm) 1.36" (34.4 mm) SM2RRV SPW604 or SPW801
  • This specification is true for thin lenses. For lenses with small focal lengths, and hence large lens curvatures, please contact tech support to ensure a proper fit.
  • This specification is the clear aperture of the mount without a retaining ring.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
LMR05V Support Documentation
LMR05VVacuum-Compatible Lens Mount with Retaining Ring for Ø1/2" Optics, 8-32 Tap
LMR1V Support Documentation
LMR1VVacuum-Compatible Lens Mount with Retaining Ring for Ø1" Optics, 8-32 Tap
LMR2V Support Documentation
LMR2VVacuum-Compatible Lens Mount with Retaining Ring for Ø2" Optics, 8-32 Tap
+1 Qty Docs Part Number - Metric Price Available
LMR05V/M Support Documentation
LMR05V/MVacuum-Compatible Lens Mount with Retaining Ring for Ø1/2" Optics, M4 Tap
LMR1V/M Support Documentation
LMR1V/MVacuum-Compatible Lens Mount with Retaining Ring for Ø1" Optics, M4 Tap
LMR2V/M Support Documentation
LMR2V/MVacuum-Compatible Lens Mount with Retaining Ring for Ø2" Optics, M4 Tap