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Post Bases![]()
BE1/M Adapter with M6 CF125 Shown with PB1 1/4" (M6) Counterbores PB2 1/4" (M6) Counterbored Slots PB4 Adapter with 1/4"-20 PF175B Shown with a Ø1.5" Pedestal Post ![]() Please Wait ![]() Click to Enlarge Ø1" and Ø1.5" Posts can be Secured to an Optical Table Using Post Base Adapters and Clamping Forks Features
Ø1" Post Bases Ø1.5" Post Bases Insights into Best Lab PracticesScroll down to read about a few things we consider when setting up lab equipment.
Click here for more insights into lab practices we follow.
Clamping Forks: Tip for Maximizing the Holding Force![]() Click to Enlarge Figure 2: More than half the total applied force (FTotal) holds the object, since L1 > L2. The height of the left leg of this CL2 clamp is variable to compensate for the object's height. This allows the clamp's top surface and the mounting surface to be made parallel.** ![]() Click to Enlarge Figure 1: Less than half the total applied force (FTotal) holds the object, since L1 < L2. The clamp illustrated above is the CL5A. Clamped objects can be fairly easy to move when the torqued screw in the clamp's slot is positioned too far from the object. Correct positioning of the screw protects clamped objects from being knocked out of position. To maximize the clamping force, position the screw as close as possible to the object.** This works since clamps like CL5A and CL2 (Figures 1 and 2, respectively) divide the torqued screw's applied force (FTotal) between two points. Clamping force F2 is applied to the object. The value of F2 is a percentage of FTotal and depends on L1 and L2, as described below. The remainder (F1) of the total force is applied through the opposite end of the clamp. The following equations can be used to calculate the two applied forces.
These equations show that the clamping force on the object increases as the distance between the object and screw decreases. The force supplied by the torqued screw is evenly divided between F1 and F2 when L1 and L2 are equal. **Note that maximizing the clamping force also requires both the top surface of the clamp and the area it contacts on the object to be parallel with the mounting surface, as depicted in Figures 1 and 2. If the tangent at the interface between the clamp and object is not parallel to the mounting surface, the force applied to the object will be divided between pressing it into and pushing it across the mounting surface. The force directed along the mounting surface may, or may not, be sufficient to translate the object. To accommodate different object heights, clamps like the CL2 have one threaded, variable-length leg, which is shown on the left in Figure 2. The number of threads between the clamp and mounting surface should be adjusted to compensate for the height of the object and to keep the clamp's top surface level with the table. Date of Last Edit: Dec. 4, 2019
Optical Tables: Clamping Forks and Distortion of the Table's Surface![]() Click to Enlarge Figure 3: The construction of a Nexus table / breadboard includes a (1) top skin, (2) bottom skin, (3) side finishing trim, (4) side panels, and (5) honeycomb core. The stainless steel top and bottom skins are 5 mm thick. Clamping forks are more rigid than the mounting surface of composite optical tables. It might be expected that the spine of the clamping fork would bend with the force exerted by the screw as the torque is increased. Instead, the screw will pull the skin of the table up and out of flat before the clamping fork deforms. Due to this, clamping forks should be used with care when securing components to optical tables. Clamping arms, which are discussed in the following, are alternatives to clamping forks that are less likely to deform the table's mounting surface. Optical Table Construction Clamping Forks When the clamp is secured by torqueing the screw, the screw pulls up on the top skin of the table (Figure 5). As the torque on the screw increases, the top skin of the table rises. Not only does pulling up on the table surface risk permanently damaging the table, this can also disturb the alignment of the optical component the clamp is being used to secure. By lifting the table's skin, the mounting surface under the clamped object tilts. ![]() Click to Enlarge Figure 6: The POLARIS-CA1/M clamping arm has a slot that accepts a mounting screw, a separate screw that applies a clamping force to an installed post, and identical top and bottom surfaces. Since a nearly continuous track around the surface of the clamping arm is in contact with the mounting surface, clamping arms cause negligible bridging effects. ![]() Click to Enlarge Figure 5: Torqueing the screw creates a force that pulls up on the table's top skin. The lifted skin tilts the mounting surface and can induce angular deviation of the object. This effect is exaggerated in the above image for illustrative purposes. ![]() Click to Enlarge Figure 4: A standard clamping fork, such as the CL5A, contacts the table along only one edge. The opposite edge is in contact with the object to be secured. A bridge forms between the two. The screw that applies the clamping force is not shown. Clamping Arms The clamping arm in Figure 6 differs from clamping forks in two significant ways. One is the surface area that makes contact with the optical table, which is highlighted in red, and the other is the method used to secure the post. The area in contact with the optical table makes a nearly continuous loop around the base of the clamp. The contact area is flat and flush with the table when the clamp is installed. The only break in the loop is a narrow slot in the vise used to grip the post. This design uses two screws, instead of the clamping fork's single screw. One screw (not shown) secures the clamp to the table, and the other (indicated) is tightened to grip the post. Since one screw is not required to perform both tasks, it is not necessary for this clamping arm to form a bridge between the clamped object and the optical table. Although the contact area is a loop, and not a solid surface, this clamp causes negligible distortion of the mounting surface. This is due to the open area inside the contact surface being narrow and surrounded by the sides of the clamp, which resist the force pulling up on the table. Date of Last Edit: Dec. 4, 2019
![]() ![]() Click to Enlarge The BE1R has a magnet in the base for stability in temporary setups. ![]() Click to Enlarge Several Slot Lengths Available
Pedestal Base Adapters The BE1(/M) base adapter is available in a pack of five for ease of ordering. Clamping Forks Fabricated from solid 303 stainless steel, all of these clamping forks create three points of contact with the table for high stability. For flexibility in the positioning of post assemblies, the CF038-P5 and CF038C(/M)-P5 forks offer 0.38" (9.5 mm) long counterbored slots, the CF125 and CF125C(/M) forks offer 1.24" (31.5 mm) long counterbored slots, the CF175 and CF175C forks have 1.75" (44.4 mm) long counterbored slots, and the CF175C/M fork has a 1.76" (44.8 mm) long counterbored slot. The counterbored slots on the CF038-P5, CF125, and CF175 forks are designed for user-supplied 1/4"-20 (M6)-threaded cap screws. For further convenience, the CF038C(/M)-P5, CF125C(/M), and CF175C(/M) forks each include a 1/4"-20 (M6)-threaded captive screw. Please note that significant over tightening of clamping forks can deform the surface of an optical table, which can cause misalignment of components and decrease stability. Our clamping forks are also available in packages of five for ease of ordering (note: the CF038-P5 and CF038C(/M)-P5 clamping forks are only available in packs of five). ![]() PB1 PB2 and PB2/M Pedestal Base Adapter ![]()
Pedestal Base Adapter Clamping Fork Made from stainless steel, the PF175B clamping fork creates three points of contact with the table for high stability. The 2.12" (53.8 mm) long counterbored slot for 1/4"-20 (M6) cap screws allows the most convenient mounting hole to be selected and creates flexibility in the positioning of post assemblies. Please note that significant overtightening of clamping forks can deform the surface of an optical table, which can cause misalignment of components and decrease stability. The PF175B clamping fork is available idividually or in packs of five. ![]()
The RB2(/M) pillar post base mounts Ø1" (25 mm) optical posts at a variable height (shown to the right). The hollow base allows the post to pass through, allowing 0.5" of post height adjustment. Translation is locked via a top-located clamping screw. ![]()
Thorlabs' Position Retainers can be used to realign posts that have been removed from an optical system. They act as markers on the breadboard or optical table in the event that you need to remove a post from your setup. The two dots near the ends of the outer arms of the retainer mark the two points of post contact. The third dot, located within the V-groove, is for retaining the position of a square base or other squared-off component. For more information on using our retainers with square components, click here. The RSPC Fixed Retainer is a compact solution for use with Ø1" and Ø1.5" Pedestal Posts. The post should be independently clamped down before aligning the RSPC retainer. After the retainer is mounted in place, the post can be removed from the setup and then later placed back into the same position. The RSPCS(/M) Swivel Retainer features a swivel head for 200° of rotational adjustment. This allows for access to additional mounting holes on the breadboard. The post should be independently locked before aligning RSPCS(/M) retainer. Partially loosen the tension adjuster screw and then mount the retainer to a breadboard tap while maintaining contact with the post. Lastly, tighten the tension adjuster screw. After this the component can be removed from the setup and then later placed back into the same position. ![]() Click to Enlarge RSPCS Swiveling Position Retainer | |||||||||||||||||
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