The C series of Ø1" (Ø25 mm) post clamps feature a precision bored Ø1" (Ø25 mm) hole with a relief cut. A clamping screw is used to squeeze the gap created by the relief cut, which in turn secures the clamp to the Ø1" (Ø25 mm) post with a great deal of force. The mounting features are summarized in the table below.
The RM series of Ø1" (Ø25 mm) post clamps feature a C-clamp design that allows them to be slipped on and off of a Ø1" (Ø25 mm) post. The clamp is secured using a non-marring brass tipped setscrew. The clamps come in a variety of styles, each with different mounting features, which are summarized in the table below.
| Imperial | Metric |
| Item # | Style | Tapped Hole for Mounting | Through Hole for Mounting | Rotating, Threaded Mounting Stud | Cage System Clamp Size |
|---|---|---|---|---|---|
| RM1A | C-Clamp | 8-32 | 8-32 | ||
| RM1B | C-Clamp | 1/4"-20 | 1/4"-20 | ||
| RM1C | C-Clamp | 8-32 | |||
| RM1D | C-Clamp with Variable Height Offset | #8 | |||
| C1026 | Relief Cut Clamp | 30 mm | |||
| C1060 | Relief Cut Clamp | 60 mm | |||
| RA90RS | Right-Angle Flexure Clamp | Ø1/2" | |||
| RM1A/M | C-Clamp | M4 | M4 | ||
| RM1B/M | C-Clamp | M6 | M6 | ||
| RM1C/M | C-Clamp | M4 | |||
| RM1D/M | C-Clamp with Variable Height Offset | M4 | |||
| C1026/M | Relief Cut Clamp | 30 mm | |||
| C1060/M | Relief Cut Clamp | 60 mm | |||
| RA90RS/M | Right-Angle Flexure Clamp | Ø12.7 mm |
For alternative thread types, consider using a thread adapter or consider a solution based on Ø1.5", Ø1/2", or Ø6 mm posts.
Thorlab's Mounting Joists provide even more space-saving options. The compact joist can be used to mount multiple optical elements close together, which alleviates the need for multiple posts and posts holders. These versatile joists can also offset a post from the mounted optic in order to squeeze the optic into tight areas. The two joist designs provide adaptable laboratory solutions to crowded table problems.


Thorlabs' selection of optomechanical parts makes it possible to easily construct entire optical systems. The Ø1" diameter post clamps featured on this page provide an excellent way to support simple single element constructions like the RM1C variable offset C-clamp being used to mount a KM100B kinematic platform with a prism to complex systems like the imaging application shown below, which demonstrates the compatibility and breadth of the Thorlabs' product line.
Starting at the fiber patch cord, the light is collimated using a FiberPort, which has an aspheric lens element that can be translated and rotated with µm level precision. The FiberPort is integrated into the 30 mm cage system (parallel steel rod structure) providing the backbone to this imaging application using the CP08FP cage plate. The next component is a kinematic turning mirror mount with a broadband dielectric mirror. Not shown in the image are the alignment tools that make iteasy to precisely align the beam path to the optical axis of the cage system. The long span of the cage system is supported by the C1026 clamp featured on this page and terminated with a cube mounted beamsplitter. Since both the turning mirror mount and the beamsplitter cube have threaded holes for the cage system rods, ERSCA adapters can be seen where the rods attach to the beamspliiter cube. The beamsplitter directs the laser down to the XY motorized translation stage (specialized microscopy stages are available) and passes the fluorescence signal being detected up to the photodiode detector. The detector is mounted on a lens tube attached to the beamsplitter cube. (Most cage system components are also lens tube compatible.) The lens tube contains a lens, filter, and ring actuated iris.
The entire setup was built on a Thorlabs' optical breadboard. In addition, elements like the fiber coupled laser source and controllers for the motorized stages are not present in the picture.
RM1A: 8-32 Tapped Hole and #8 Counterbored Through Hole
RM1A/M: M4 Tapped Hole and M4 Counterbored Through Hole
RM1B: 1/4"-20 Tapped Hole and 1/4"-20 Through Hole
RM1B/M: M6 Tapped Hole and M6 Through Hole
RM1C: 8-32 Rotating Threaded Stud
RM1C/M: M4 Rotating Threaded StudRM1A (RM1A/M) and RM1B (RM1B/M) C-Clamps for Ø1" (Ø25 mm) posts each have two mounting points located 90° apart for perpendicular mounting of components. One of the mounting points has a tapped hole while the other has a counterbored through hole. Alternatively, the RM1C (RM1C/M) has one mounting point with a rotating threaded mounting stud. The C-clamp design allows the clamp to be slipped on and off the post easily. Simply loosen or tighten the brass tipped (non-marring) setscrew that locks the C-clamp to the Ø1" (Ø25 mm) post.
Part Number |
Description |
Price |
Availability |
|---|---|---|---|
RM1A |
Ø1" Post Clamp, 8-32 Mounting |
$25.20 |
Today |
RM1B |
Ø1" Post Clamp, 1/4"-20 Mounting |
$25.20 |
Today |
RM1C |
Ø1" Post Angle C-Clamp, 8-32 Threaded Stud |
$47.40 |
Today |
RM1A/M |
Ø1" (Ø25 mm) Post Clamp, M4 Mounting |
$25.20 |
Today |
RM1B/M |
Ø1" (Ø25 mm) Post Clamp, M6 Mounting |
$25.20 |
Today |
RM1C/M |
Ø1" (Ø25 mm) Post Angle C-Clamp, m4 Threaded Stud |
$47.40 |
Today |
The RA90RS clamp allows a Ø1/2" TR post to be mounted perpendicularly to a Ø1.0" RS post. The design, which is based off of the RA90 Right-Angle Post Clamp, combines a highly stable clamp flexure lock with a thumbscrew locking mechanism to provide a solution that enables a Ø1/2" post to be mounted perpendicular to a Ø1" post. The center-to-center distance between the Ø1.0" and Ø1/2" posts is 1" for the imperial version (25.0 mm for the metric version).
Part Number |
Description |
Price |
Availability |
|---|---|---|---|
RA90RS |
Ø1" to Ø1/2" Right-Angle Post Clamp |
$25.00 |
Today |
RA90RS/M |
Ø25 mm to Ø12.7 mm Right-Angle Post Clamp, Metric |
$25.00 |
Today |
RM1D: #8 Counterbored Through Hole
RM1D/M: M4 Counterbored Through Hole
RM1D (RM1D/M) Variable Offset C-Clamps for Ø1" (Ø25 mm) posts have a mounting surface that can be varied in position over a range of 0.4" (10 mm) in addition to a fixed position tapped mounting hole on the backside of the clamp. The variable position mounting surface has either a tapped or counterbored through hole (model dependent) and it is locked in place using a thumbscrew. The C-clamp design allows the clamp to be slipped on and off the post easily. Simply loosen or tighten the brass tipped (non-marring) setscrew that locks the C-clamp to the Ø1" (Ø25 mm) post.
Part Number |
Description |
Price |
Availability |
|---|---|---|---|
RM1D |
Adjustable C-Clamp for Ø1" Post, #8 Through Hole |
$50.40 |
Today |
RM1D/M |
Adjustable C-Clamp for Ø1" (Ø25 mm) Post, M4 Through Hole |
$50.40 |
Today |
Quick-Connect Cage Clamp
Easy Drop-In/Drop-Out of Cage Systems
Single Locking Screw Allows One-Handed Operation
Compatible with Ø1" (Ø25 mm) RS Series Posts
The C1026 (C1026/M) and C1060 (C1060/M) relief cut clamps for Ø1" (Ø25 mm) posts are designed to support 30 mm and 60 mm cage systems, respectively. Two parallel cage rods can be placed in the clamp and with a single screw they can be locked in place. In this way, complete sections of cage systems can be supported by a single post as can be seen in the application image at the top of the page. The clamp itself has a precision Ø1" hole bored through it with a relief cut. A 1/4"-20 (M6) caphead screw can be tightened to compress the gap created by the relief cut, which results in the C10 Series being secured to the Ø1" (Ø 25 mm) post with a great deal of force.
Part Number |
Description |
Price |
Availability |
|---|---|---|---|
C1026 |
30 mm Cage Clamp for Ø1" Posts |
$71.00 |
Today |
C1060 |
60 mm Cage Clamp for Ø1" Posts |
$79.00 |
Today |
C1026/M |
30 mm Cage Clamp for Ø25 mm Posts, Metric |
$71.00 |
Today |
C1060/M |
60 mm Cage Clamp for Ø25 mm Posts, Metric |
$79.00 |
Today |


Thorlabs’ Mounting Joists provide valuable space-saving mounting options, ideal for crowded optical tables or breadboards. These mounts are compatible with our Ø1/2” and Ø1” posts and allow multiple optics may be mounted close together on a single joist, eliminating the need for multiple posts and post holders.
The PJ301(/M) enables centered-mounting (optics may be placed on both sides of post center) and features a centered, counterbored hole for an 8-32 (M4) cap screw for post mounting and counterbored slots for an 8-32 (M4) cap screw and #8 nut (M4 nut). This joist allows an optic to be offset by 0.40" - 1.40" (10.16 - 35.56 mm) from post center.
The PJ302(/M) enables offset-mounting (optics may be offset to one side only) and features counterbored slots for an 8-32 (M4) cap screw for post mounting and a counterbored slot for an 8-32 (M4) cap screw and #8 nut (M4 nut). This joist allows an optic to be offset by 0.40" - 2.70" (10.16 - 68.58 mm) from post center.
Please Note: Imperial nuts only fit the imperial joists; metric nuts only fit the metric joists (nuts included).
Part Number |
Description |
Price |
Availability |
|---|---|---|---|
PJ301 |
Center Mount 3" Post Joist |
$16.00 |
Today |
PJ302 |
Reaching 3" Post Joist |
$15.00 |
Today |
PJ301/M |
Center Mount 3" Post Joist (Metric) |
$16.00 |
Today |
PJ302/M |
Reaching 3" Post Joist (metric) |
$15.00 |
Today |