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Clamping Forks for Ø1/2" Post Holders and Ø1" Pedestal Posts![]()
0.38" (9.5 mm) 0.59" (14.9 mm) Counterbored Slot CF125C CF038-P5 Pack of 5 PF175B 1.30" (33.0 mm) 0.63" (15.9 mm) Clearance Slot 1.24" (31.5 mm) 0.75" (19.1 mm) 2.12" (53.8 mm) MSC2 MSC3 POLARIS-SCA1 POLARIS-CA1 Contact Pads Post and ![]() Please Wait Features
Thorlabs offers clamping forks to secure our pedestal-style Ø1/2" post holders, Ø1" post holders, Ø1" pedestal posts, Ø12 mm pedestal posts, or Mini-Series post holders to breadboards and optical tables. With slots ranging from 0.38" to 2.12" (9.5 mm to 53.8 mm) in length, each fork can swivel around the pedestal-style post holder or post to access the most convenient mounting holes on the optical table or breadboard. Thorlabs also manufactures Polaris® Non-Bridging Clamping Arms for Ø1" or Ø25 mm posts, which provide high holding force with minimal torque. Our base adapters thread onto the bottom of our standard Ø1/2" post holders, Ø1" post extensions, or Ø1.5" posts to convert them into pedestal-style posts. The clamping forks can then be used to hold the posts or post holders in place by clamping over the base adapter. Please note that significant overtightening of clamping forks can deform the surface of an optical table, which can cause misalignment of components. This effect is minimized with the use of Polaris Clamping Arms; see below for details. An alternative method for securing Ø1" and Ø1.5" pedestal posts is a pair of CL8 table clamps. These compact pieces are part of our larger selection of table clamps and allow users to secure posts to breadboards and tables with limited space. Insights into Best Lab PracticesScroll down to read about a few things we consider when setting up lab equipment.
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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 An MSC2 Clamping Fork secures a Mini-Series pedestal post to a breadboard with 1/4"-20 tapped holes.
Our clamping forks are designed to provide exceptional clamping force when used with our Ø12 mm pedestal posts or our pedestal-base post holders. These clamping forks provide flexibility for building setups that combine Mini-Series components and our larger range of optomechanics offerings. The MSC1 and MSC2 are made from anodized aluminum, while the MSC3 is made from precipitation hardened 17-4PH stainless steel to provide a more uniform clamping force. Designed to be used with the Mini-Series breadboards, the MSC1 and MSC3 are compatible with a 4-40 (M3) and 8-32 (M4) cap screw, respectively. The MSC2 slot accepts 1/4"-20 (M6) cap screws, thus enabling the inclusion of Mini-Series posts and components into setups on standard breadboards and optical tables in addition to mini-series breadboards. Each clamping fork features landing pads on the bottom surface to maximize stability when using a washer and cap screw to lock down a post with the fork. Please note that significant overtightening of clamping forks can deform the surface of an optical table, which can cause misalignment of components. ![]() ![]() Click to Enlarge The BE1R has a magnet in the base for stability in temporary setups. ![]() Click to Enlarge A CF125 fork is used to secure a Ø1/2" post holder to an optical table with a BE1 base. ![]() 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 Made from solid 303 stainless steel, the CF038-P5, CF125, and CF175 clamping forks create three points of contact with the table for high stability. For flexibility in the positioning of post assemblies, three sizes are available: the CF038-P5 fork offers a 0.38" (9.5 mm) long counterbored slot, the CF125 fork offers a 1.24" (31.5 mm) long counterbored slot, and the CF175 fork has a 1.75" (44.4 mm) long counterbored slot. All three counterbored slots are designed for 1/4"-20 (M6)-threaded cap screws. 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. These clamping forks are available with a 1/4"-20 (M6)-threaded captive screw. For more information, please see below. Clamping forks are also available in packs of five for ease of ordering (note: the CF038-P5 clamping fork is only available in packs of five). ![]() ![]() Click for Details Bottom view of the captive screw held in the slot by a retainer.
Our Clamping Forks offer the convenience of 1/4"-20 (M6) captive screws, while still providing the same exceptional clamping force for our pedestal-style posts and post holders as our standard forks, sold above. The screws can be tightened into the breadboard using a 3/16" (5 mm) hex key or balldriver. Please note that significant over tightening of clamping forks can deform the surface of an optical table, which can cause misalignment of components. 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, Thorlabs offers three sizes: the CF038C(/M)-P5 fork has a 0.38" (9.5 mm) long counterbored slot, the CF125C(/M) fork has a 1.24" (31.5 mm) long counterbored slot, the CF175C fork has a 1.75" (44.4 mm) long counterbored slot, and the CF175C/M fork has a 1.76" (44.8 mm) long counterbored slot. When used with the BE1(/M) base adapter (sold above), these clamping forks can position our standard Ø1/2" post holders or Ø1" post extensions. Alternatively, the clamping fork is directly compatible with our pedestal-style Ø1/2" post holders or Ø1" pedestal posts. These clamping forks are also available in packs of five for ease of ordering (note: the CF038C(/M)-P5 clamping fork is only available in packs of five). ![]()
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. ![]() ![]() Click to Enlarge Click for POLARIS-CA1/M Holding Torque Results* The Polaris clamping fork design has undergone extensive testing to ensure high-quality performance. See the full presentation for more details. *It is important to note that the 1/4"-20 and M6 x 1.0 clamping torque values have been adjusted to provide the same clamping post and table forces. Also note that the maximum recommended tightening torque for an 18-8 stainless steel screw is 75.2 in-lbs for a 1/4"-20 screw and 8.8 N-m for an M6 x 1.0 screw. Higher mounting torques can cause the screw to fail. ![]() Click to Enlarge The arm can be mounted with either flat surface in contact with the table, allowing for compact setups. ![]() Click to Enlarge Side-Located 1/4"-20 (M6) Screw Actuates Clamping Bore
The Polaris® Clamping Arms are the ideal solution for stably mounting our Ø1" or Ø25 mm Posts for Polaris Mounts or Ø1" Monolithic Polaris Mount. Each clamping arm, which is machined from heat-treated, stress-relieved stainless steel bar stock, provides extremely high holding forces with minimal torquing of the mounting screws (see the graph to the right). The flat, non-bridging top and bottom surfaces of each clamping arm allow it to be used with either side in contact with an optical table or other mounting surface. This feature allows the clamp to be positioned in left- or right-handed orientations and optical components to be placed in near contact to one another while minimizing the footprint (see the image to the left). On each side of the arm, a relief cut around the slot protects the ±0.001" (±0.02 mm) flat surface from any marring due to the screw and washer, allowing for more stable mounting. The clamping arms are offered with slot lengths of 0.75" (19.1 mm) or 1.30" (33.0 mm), providing flexibility when used in applications such as tight laser cavity setups. Four of our clamping arms are designed to hold Ø1" posts, while the remaining two are designed to hold Ø25 mm posts; see the table below for details. Note the arms with a Ø1" (25.4 mm) bore are not compatible with Ø25 mm posts; the bore diameter is too large and will not contact the post when clamping. Non-Bridging Design: Industry Standard Clamping Fork
|
Item # | Compatible Post Size |
Clamping Screw |
Slot Length | Footprint |
---|---|---|---|---|
POLARIS-SCA1 | Ø1" (25.4 mm) |
1/4"-20 (3/16" Hex) |
0.75" (19.1 mm) |
2.78" x 1.60" (70.5 mm x 40.6 mm) |
POLARIS-CA1 | 1.30" (33.0 mm) |
3.33" x 1.60" (84.5 mm x 40.6 mm) |
||
POLARIS-SCA1/M | M6 x 1.0 (5 mm Hex) |
0.75" (19.1 mm) |
2.78" x 1.60" (70.5 mm x 40.6 mm) |
|
POLARIS-CA1/M | 1.30" (33.0 mm) |
3.33" x 1.60" (84.5 mm x 40.6 mm) |
||
POLARIS-SCA25/M | Ø25.0 mm (Ø0.98") |
0.75" (19.1 mm) |
2.78" x 1.60" (70.5 mm x 40.6 mm) |
|
POLARIS-CA25/M | 1.30" (33.0 mm) |
3.33" x 1.60" (84.5 mm x 40.6 mm) |
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