Alignment Stops
![](https://punchout.webdev02.thorlabs.com/Images/GuideImages/7297_AlignmentStops_3.jpg)
- Interchange or Rotate Post-Mounted Components without Altering Height
- Mark Position of Cage Components without Disturbing Alignment
ERCPS
R2T
R2
Two ERCPS Cage Plate Stops Used
to Mark the Position of a 30 mm Cage Plate
RMC
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Features
- Alignment Stops for Ø1/2" Posts and Cage Components
- Position-Maintaining Post Collar Maintains Height and Rotational Orientation
- Cage Plate Stops for Ø6 mm Cage Rods
These alignment stops provide a quick and easy way to remove components from a post holder or cage system and return them to their original position. Made from anodized aluminum, each stop can be put in place without disturbing alignment or disassembling the system. The R2(/M) or R2T Slip-On Post Collar can be used to finely adjust the height of the post using an included, vertically mounted setscrew. The RMC Position-Maintaining Post Collar is a two-piece set that locks onto a Ø1/2" post and post holder to maintain both height and rotational orientation with maximum repeatability. As an alternative option, rotational orientation can also be maintained using our R2 and R2T post collars if they are used with our anti-rotation adapter. The ERCPS Cage Plate Stops secure to our Ø6 mm Cage Rods, allowing cage components to be moved and repositioned easily within a cage system.
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![](https://punchout.webdev02.thorlabs.com/images/TabImages/Post_Collar_Slip-On_A1-140.jpg)
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A vertical setscrew allows for fine adjustment of the post height.
- 0.44" (11.2 mm) Thick
- Includes Vertically Aligned 4-40 Setscrew
- Packs of Five Also Available
The R2(/M) Slip-On Collar locks onto a Ø1/2" post with a thumbscrew. By positioning the collar on a post so that it rests on the top of the post holder, the post can be rotated without altering the height of the mounted component. In addition, the R2 is equipped with a 4-40 setscrew. By using a 0.050" (1.3 mm) hex key, this adjustment screw allows for approximately 0.25" (6.4 mm) of post height adjustment (see photo to the right) without the need for a translating post or post holder. To restrict the rotation of the post, the R2 can be paired with the TRK05 anti-rotation adapter.
![](https://punchout.webdev02.thorlabs.com/images/arrow_Vert.gif)
![](https://punchout.webdev02.thorlabs.com/images/TabImages/Post_Collar_Thin_A1-150.jpg)
Click to Enlarge
The R2T collar marks the vertical position of a post inside a post holder.
- 0.23" (5.7 mm) Thick
- Thin Design Enables Easy Incorporation in Tightly Spaced Setups
- Sold in Packs of Five
The R2T is a thinner version of the R2 Post Collar featured above and can be secured to a Ø1/2" post by turning the included 8-32 brass-tipped locking screw. By placing the collar on a post so that it rests on the top of the post holder, the post can be rotated or removed and replaced without altering the height of the mounted component. At a thickness of only 0.23", the R2T collar occupies minimal space on the post and allows any mounted component to be positioned vertically close to the post holder.
To restrict the rotation of the post, the R2T can be paired with the TRK05 anti-rotation adapter. Alternatively, each R2T has a small groove, shown in the photo to the left, that allows it to be used as an extra post collar in setups using the RMC Position-Maintaining Post Collar (available below).
![](https://punchout.webdev02.thorlabs.com/images/arrow_Vert.gif)
![](https://punchout.webdev02.thorlabs.com/images/tabimages/Post_Collar_Rotation_A1-150.jpg)
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RMC Post Collar Maintains Height and Rotational Orientation
Position-Maintaining Post Collar Usage
- Two-Piece Post Collar Maintains Height and Rotational Orientation
- Steel Ball and V-Groove Provides ≤0.5° Angular Repeatability
- Holds Height Position to within 0.010" (0.3 mm)
Thorlabs' RMC Position-Maintaining Post Collar is designed to maintain the established height and rotational orientation of a Ø1/2" Post and Post Holder within a setup. The collar is a two-piece set: a 0.47" (11.9 mm) thick, engraved post holder collar and a thinner, 0.23" (5.7 mm) thick post collar. A steel ball and matching V-groove combination provide ≤0.5° angular repeatability.
As seen in the animation to the right, to use the RMC, slip the post holder collar on top of a Ø1/2" post holder and then secure its position using a 5/64" (2 mm) hex key to tighten the 8-32 nylon-tipped setscrew. Then, set the post height position by seating the post collar such that the V-groove sits on top of the protruding steel ball (see the image to the right). Secure the post collar to the post using a 5/64" (2 mm) hex key to tighten the brass-tipped 8-32 setscrew. Once assembled, small rotational adjustments can be achieved by loosening the setscrew in the lower collar and rotating until the desired position is reached.
The RMC post collar can be used to quickly swap optomechanical components between different posts while keeping the same height and rotational orientation. Each component to be swapped should be fitted with the post collar at the desired height. For best results, the post holder collar should be positioned so that the setscrew is opposite the spring-loaded thumbscrew (as shown in the image to the right). While making adjustments to the rotational position of the bottom collar, ensure that there is a preload from the post holder’s thumbscrew against the post; this ensures that the two-line contact between the post holder and mating post is maintained during the adjustment.
![](https://punchout.webdev02.thorlabs.com/images/arrow_Vert.gif)
![](https://punchout.webdev02.thorlabs.com/images/TabImages/Optical_Cage_Plate_Clamp_A1-250.jpg)
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ERCPS Cage Plate Stops snap onto cage rods without any disassembly of the cage system.
![](https://punchout.webdev02.thorlabs.com/images/TabImages/Optical_Cage_Plate_Stops_A1-200.jpg)
Click to Enlarge
ERCPS Cage Rod Stops can mark the position of cage components.
- Marks the Position of Cage Components
- Flexure Clamping Mechanism
- Sold in Packs of Four
ERCPS Cage Plate Stops mark the position of a cage plate, allowing it to be reliably moved and repositioned in a cage system. These clamps are 0.14" (3.6 mm) thick and are compatible with our Ø6 mm cage rods for 30 mm and 60 mm cage systems. Utilizing a flexure design, the clamps are secured in place using a 0.05" (1.3 mm) hex key. They can be easily clamped onto the middle of a cage rod without removing other components.