Ø1" (Ø25.0 mm) Pillar Posts

• Directly Mount Optomechanical Components
• Extend the Height of Our Ø1" Pedestal Posts
• 8-32 Tapped Hole on Both Ends
• Torque Hole for 3/16" Balldriver or SPW501 Spanner Wrench Provides Extra Leverage During Tightening

These pillar posts are machined from nonmagnetic 303 stainless steel and provide strong support in an optical setup. By combining the rigidity of these solid Ø1" posts with Ø1" post mounts or Ø1" post holders, any arbitrary height support structure can be constructed. Each post is machined with a 8-32 tapped hole in both ends for direct mounting to an optical mount and breadboard. These posts can be adapted to bases with 1/4" (M6) counterbores by using SD1 counterbore adapters.

8-32 setscrews, available in our HW-KIT3 hardware kit, can be used to secure posts on top of each other, or to our Fixed Lens Mounts with Internal Threads. 

• Directly Mount Optomechanical Components
• Extend the Height of Our Ø25.0 mm Pedestal Posts
• M4 Tapped Hole on Both Ends
• Torque Hole for 5 mm Balldriver or SPW501 Spanner Wrench Provides Extra Leverage During Tightening

These pillar posts are machined from nonmagnetic 303 stainless steel and provide strong support in an optical setup.By combining the rigidity of these solid Ø25.0 mm posts with Ø25.0 mm post mounts or Ø25.0 mm post holders, any arbitrary height support structure can be constructed. Each post is machined with a M4 tapped hole in both ends for direct mounting to an optical mount and breadboard. These posts can be adapted to bases with M6 (1/4") counterbores by using SD1 counterbore adapters.

M4 setscrews, available in our HW-KIT3/M hardware kit, can be used to secure posts on top of each other, or to our Fixed Lens Mounts with Internal Threads.

• Extend the Height of Our Ø1" Pedestal Posts
• 1/4"-20 Tapped Hole on Both Ends
• Torque Hole for 3/16" Balldriver or SPW501 Spanner Wrench Provides Extra Leverage During Tightening

These pillar posts provide strong support in an optical setup. By combining the rigidity of these solid Ø1" posts with our high stability RB2 base, any arbitrary height support structure can be constructed. Each post is machined with a 1/4"-20 tapped hole in both ends for direct mounting to an optical table or standard base and an optical mount. These posts are machined from nonmagnetic 303 stainless steel.

To convert the 1/4"-20 taps to 8-32 taps, we separately offer the AE8E25E thread adapter, which has external 1/4"-20 threading and internal 8-32 threading. The adapter can be used with an 8-32 setscrew to attach many of Thorlabs' imperial optomechanical parts to a Ø1" imperial pillar post. In principle, the adapter can also be used to connect two pillar posts, but a solid 1/4"-20 setscrew, which is included in our HW-KIT4 hardware kit, is a more stable choice for this.

• Extend the Height of Our Ø25.0 mm Pedestal Posts
• M6 Tapped Hole on Both Ends
• Torque Hole for 5 mm Balldriver or SPW501 Spanner Wrench Provides Extra Leverage During Tightening

These pillar posts provide strong support in an optical setup. By combining the rigidity of these solid Ø25.0 mm posts with our high stability RB2 base, any arbitrary height support structure can be constructed. Each post is machined with an M6 tapped hole in both ends for direct mounting to an optical table or standard base and an optical mount. These posts are machined from nonmagnetic 303 stainless steel.

To convert the M6 taps to M4 taps, we separately offer the AE4M6M adapter, which has external M6 threading and internal M4 threading. The adapter can be used with an M4 setscrew to attach many of Thorlabs' metric optomechanical parts to a Ø25.0 mm metric pillar post. In principle that adapter can also be used to connect two pillar posts but a solid M6 setscrew as included in the hardware kit HW-KIT4/M will provide a more stable solution.

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Top and Bottom Views

• Counterbore Mounting Hole for #8 (M4) Screw and Washer
• Two Ø2 mm Alignment Pin Holes Around Mounting Hole for Precision Mounting (Dowel Pins Not Included)
• Vacuum Compatible to 10^-9 Torr at 25 °C with Proper Bake Out
• 303 Stainless Steel Heat-Treated to Remove Internal Stresses for Increased System Stability
• Large-Diameter Relief Cut on Top and Bottom for Additional Mounting Stability

These posts are machined from heat-treated stainless steel to provide stable support for attached mounts. Heat treating the materials removes the internal stresses that can cause temperature-dependent hysteresis. All of our Polaris mirror mounts, clamping arms, and 45° adapters are constructed from this same material, which has a relatively low coefficient of thermal expansion (CTE). Matching the CTE of materials within an optical setup is essential to achieve optimal thermal repeatability.

These posts feature a #8 (M4) counterbore hole for mounts with threaded mounting holes up to Ø2". The top of the posts have two Ø2 mm alignment pin holes, which are located on either side of the counterbore hole. Dowel pins are not included. These posts are designed to mount to an optical surface using our non-bridging clamping arms for Ø1" posts.

A Ø6 mm alignment bore is located 20 mm from the base and can be used in combination with our cage rods for the alignment of multiple mounts along a common optical axis or for fine angle tuning. Note that the alignment bore does not go completely through the PLS-C1 and PLS-C246/M posts. Instead, these posts contain two bores on opposite sides, within ±0.3°, that are 0.20" (5.1 mm) deep. Given their shorter length, a through bore would interfere with the counterbore and prevent components from being securely attached to the post.

Popular post lengths are available from stock; custom lengths can be requested by contacting Tech Sales. Since the counterbore posts require clamping arms for Ø1" posts or other optomechanical components for mounting to an optical surface, the minimum length for custom posts should not be less than the height of the mounting component, which is 0.60" (15.2 mm) for these clamping arms.

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Directly attach a Polaris mount via a top-located 8-32 (M4) mounting hole without the need for a thread adapter. Dowel pins (not included) provide precision mounting.

• One or Three Top-Located 8-32 (M4 x 0.7) Mounting Holes
• One Bottom-Located 1/4"-20 (M6 x 1.0) Mounting Holes
• Two Ø2 mm Alignment Pin Holes Around Each Tap for Precision Mounting (Dowel Pins Not Included)
• Vacuum Compatible to 10^-9 Torr at 25 °C with Proper Bake Out
• 303 Stainless Steel Heat-Treated to Remove Internal Stresses for Increased System Stability
• Large-Diameter Relief Cut on Top and Bottom for Additional Mounting Stability
• Configurator Available Below for Custom Lengths and Usage Features

Our Posts for Polaris^® Mounts are machined from heat-treated stainless steel to provide stable support for our Polaris Mirror Mounts. Heat treating the materials removes the internal stresses that can cause temperature-dependent hysteresis. All of our Polaris mirror mounts, clamping arms, and 45° adapters are constructed from this same material, which has a relatively low coefficient of thermal expansion (CTE). Matching the CTE of materials within an optical setup is essential to achieve optimal thermal repeatability.

Each post contains one or three top-located 8-32 (M4 x 0.7) mounting holes and a bottom-located 1/4"-20 (M6 x 1.0) mounting hole. The 8-32 (M4 x 0.7) threads allow a mirror mount to be attached directly to the post, eliminating the need for thread adapters and thereby reducing the instability created when stacking multiple optomechanical components.

Versions of these posts with a single 8-32 (M4 x 0.7) mounting hole can be used with our smaller Polaris mounts, while the posts with three 8-32 (M4 x 0.7) mounting holes are ideal for securing larger Ø2" and Ø3" Polaris mounts with more than one screw. Popular post lengths are available from stock; custom lengths can be requested using the configurator below (single-mounting-hole versions only) or by contacting Tech Support.

Created with OEM and custom systems in mind, each post features holes for DIN-7m6 ground dowel pins (not included) on either side of the central threaded hole at each end to aid with alignment. Securing posts and accessories within a system using dowel pins prevents them coming loose due to vibrations, shipping, or incidental contact.

Our Non-Bridging Clamping Arms, available below, are the ideal mounting solution for these posts. These clamping arms feature a non-bridging design that reduces the gap, or “bridge,” that traditionally results between the back of a standard clamping fork and a Ø1" pedestal post base.

Click here for more information on these posts including OEM mounting options, mounting stability details, and test data.

OEM Solutions and Volume Orders

Thorlabs manufactures custom and high-volume Polaris products for use in custom and OEM systems. See our custom configurator below for our custom post options. High-volume discounts are built into the configurator, with a minimum order size of 26 posts required to receive the discount.

For pricing information on high-volume orders of our standard posts, please contact OEM Sales.

Alignment Bore
A Ø6 mm bore is located 20 mm above the base of the post to allow for fine alignment. The alignment bore will not be covered when these posts are secured with a non-bridging clamping arm, sold below. Please note that this bore does not go completely through the posts with lengths of 1.0" or shorter; these posts contain two bores on opposite sides, within ±0.3°, that are 0.20" (5.1 mm) deep. Given their shorter length, a through bore would interfere with the mounting threads, preventing anything from being securely attached to the post. Any post with a length of 1.49" (37.6 mm for metric posts) or less will have a similar alignment bore configuration.

Cleanroom and Vacuum Compatibility
These posts are designed to be compatible with cleanroom and vacuum applications. They are chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, they are double vacuum bagged so that they can be transported into a cleanroom environment without introducing contamination. Please contact Tech Support for details.

• Green Shaded Cells Denote Standard Optical Axis Heights
• Excluding the POLARIS-K05P2 Ø1/2" Mirror Mount with Piezo Adjusters

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POLARIS-B2S Mount with DMLP490L Beasmplitter on RS4P8T Post in
POLARIS-CA1 Clamping Arm

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Back View of RS4P8C Post

• Posts with Taps or Clearance Holes Through the Side for Constructing Custom Mounting Configurations
  • RS4P8T (RS100P4T/M): Three 8-32 (M4 x 0.7) Tapped Holes
  • RS4P8C (RS100P4C/M): Three #8 (M4) Clearances Holes in a Counterbored Slot
• Two Torque Holes for 3/16" (5 mm) Balldriver Provide Extra Leverage During Tightening
• 8-32 (M4 x 0.7) Tapped Hole on Each End

These construction posts are designed for mounting optomechanical components in custom configurations. The RS4P8T (RS100P4T/M) post offers three 8-32 (M4) tapped holes and two mounting flats, while the RS4P8C (RS100P4C/M) post offers three #8 (M4) clearance holes in a counterbored slot and one mounting flat. A single construction post may be used to mount an optomechanical component on its side, as shown in the photo to the right. Additionally, the two construction post variants can be combined using a cap screw, as shown below, to enable mounting components at an arbitrary angle. Each end of these posts has an 8-32 (M4 x 0.7) tapped hole.

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RS4T and RS4C Posts with RSH1.5 Post Holder and PF125B Clamp Combined for Mounting at Arbitrary Angles

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Back View of RS4C Post

• Posts with Taps or Clearance Holes Through the Side for Constructing Custom Mounting Configurations
  • RS4T (RS100T/M): Three 1/4"-20 (M6 x 1.0) Tapped Holes
  • RS4C (RS100C/M): Three 1/4" (M6) Clearances Holes in a Counterbored Slot
• Two Torque Holes for 3/16" (5 mm) Balldriver Provide Extra Leverage During Tightening
• 1/4"-20 (M6 x 1.0) Tapped Hole on Each End

These construction posts are designed for mounting optomechanical components in custom configurations. The RS4T (RS100T/M) post offers three 1/4"-20 (M6 x 1.0) tapped holes and two mounting flats, while the RS4C (RS100C/M) post offers three 1/4" (M6) clearance holes in a counterbored slot and one mounting flat. A single construction post may be used to mount an optomechanical component on its side. Additionally, the two construction post variants can be combined using a cap screw, as shown in the photo to the right, to enable mounting components at an arbitrary angle. Each end of these posts has a 1/4"-20 (M6 x 1.0) tapped hole.

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Comparison of thermal conduction in stainless steel and fiberglass pillar posts.

• Ø1" (Ø25.0 mm) Pillar Posts Made from G10/FR4 Fiberglass
• Low Thermal Conductivity: 0.29 W/m•K
• High Electrical Resistivity: 1.00 x 10¹¹ Ω•cm
• Max Operating Temperature: 70 °C
• 1/4"-20 (M6 x 1.0) Threaded Inserts in Both Ends
• Torque Hole for 1/8" (3 mm) Balldriver Provides Extra Leverage During Tightening
  • Max Torque: 75 lb-in (8.4 N•m)

Thorlabs' Ø1" (Ø25.0 mm) fiberglass posts provide thermal and electrical isolation between the mounted device(s) and the breadboard surface. Each post end features threaded steel inserts and a machined dot on top of each metric post denotes a metric threaded insert. The G10/FR4 fiberglass construction features excellent insulation compared to stainless steel (see the isolated posts page for details). These posts have the same profile as our Ø1" (Ø25.0 mm) stainless steel pillar posts (Item #s RS1, RS2, RS25/M, and RS50/M).

The plot to the right depicts the measured temperatures of a heated breadboard and the tops of four attached Ø1" posts, including stainless steel and fiberglass variants. The data illustrates the increased thermal insulation of our G10/FR4 fiberglass pillar posts compared to stainless steel posts.

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Deep Base Allows Height Adjustment

• RB2 Base Allows Post Extensions to be Used as a Variable Height Mounting Structure
• Hollow Base Allows Post Extension to Pass Through for 0.5" of Height Adjustability
• Convenient Vertically Accessed Locking Screw

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.

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SPW501 Spanner Wrench Being Used to Tighten a Small Ø1" Post Spacer onto a Ø1" Pillar Post

• Solid Stainless Steel Construction
• 1/4"-20 (M6) Tapped Hole
• Large Diameter Relief Cut on Top and Bottom for Additional Mounting Stability
• Spanner Wrench Slots

These small post spacers are designed for achieving "in between" heights of our Ø1" (Ø25.0 mm) Posts without compromising structural rigidity. The center 1/4"-20 (M6) tapped through hole allows threaded studs to pass through to the mating tap of the components on the top and bottom. Each spacer ≤0.31" (8 mm) long features two slots on the side that allow it to be securely tightened onto a post using the SPW501 spanner wrench (sold below), as shown in the image to the right. Spacers with lengths 0.35" (9 mm) or larger feature a through hole instead of the two slots; this through hole accepts a 1/8" (3 mm) balldriver as well as the SPW501 for providing leverage while tightening or loosening.

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Post Spacer Being Used to Increase the Post Height
by 5 mm (0.2")

• Solid Stainless Steel Construction
• Clearance Holes Accept Ø1/4" (M6) Screws
• ≥1 mm Thick Spacers have Large Diameter Relief Cuts on Top and Bottom for Additional Mounting Stability

These spacers are designed for achieving heights in between those of our catalog Ø1" (Ø25 mm) Posts offering without compromising structural rigidity. The center clearance hole allows Ø1/4" (M6) threaded studs to pass through to the mating tap of the components on either side of the spacer. Achieving, for example, a total post height of 8.2" is as simple as inserting one RS5M spacer (0.2" thickness) in between two RS4 posts (4" length).

Note that spacers 0.9 mm and thinner have an indent on the side due to the manufacturing process. This feature is cosmetic and does not interfere with the spacer's functionality.

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Hold the knife edge at a 45° angle to the shim
to peel away layers.

• Peel Away Individual Layers as Needed
• Stainless Steel
• Tabbed for Easy Peeling
• Sold in Packs of 5

This Ø25 mm, peelable, laminated shim provides fine height adjustment when using our Ø1" posts. These 1.0 mm ± 10% thick shims come in packs of 5 and have 14 layers, which are each 0.075 mm thick. They have a through hole to accommodate a 1/4"-20 (M6) screw.

Be aware the finish on some shims may appear tarnished due to the manufacturing process. This does not affect form, fit, or function. Only the appearance is altered.

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The RS1LM Shown Separating the RS2P Post and the PRM1 Rotation Mount

To peel, take a sharp edge like a box cutter and hold it at a 45° angle to the tab on the shim as shown in the photo to the right. Gently flick the knife upward until the layer begins to lift. In general, you should be able to lift an edge within 5 attempts. If you cannot get an edge to lift, gently tap the corner of the tab on a table until the material begins to flare.

Once an edge is lifted, insert the blade under the layer, squeeze the layer between your thumb and the blade, and roll your wrist down and then up to start peeling (see photo in the upper left). Once the layer has been peeled up enough, you can use your thumb and forefinger to remove it the rest of the way. Repeat this process until you have removed as many layers as desired. Discard all peeled-off layers.

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The BE1R has a magnet in the base for stability in temporary setups.

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These base adapters feature a 1/8" (3 mm) hex socket on the bottom for tightening.

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The CF038C(/M)-P5, CF125C(/M), and CF175C(/M) each offer a captive screw.

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Several Slot Lengths Available

• BE1(/M) and BE1R(/M) Adapters Convert Standard Ø1/2" Post Holders and Ø1" Posts into Pedestal-Style Mounts
• Clamping Fork or CL8 Table Clamp Secures Pedestal-Style Mount to a Breadboard or Optical Table
• Three Sizes Provide Clamping with 1/4"-20 (M6) Cap Screws
  • 0.40" (10.2 mm) Long Counterbored Slot [CF038-P5 and CF038C(/M)-P5]
  • 1.24" (31.5 mm) Long Counterbored Slot [CF125 and CF125C(/M)]
  • 1.75" (44.4 mm) Long Counterbored Slot [CF175 and CF175C(/M)]
• Swivel Clamping Fork 360° to Select Most Convenient Mounting Hole
• CF038C(/M)-P5, CF125C(/M) and CF175C(/M) Each Include a 1/4"-20 (M6)-Threaded Captive Screw
• BE1(/M) and All Clamping Forks Available in Packs of Five [CF038-P5 and CF038C(/M)-P5 Not Sold Individually]

Pedestal Base Adapters
The BE1(/M) and BE1R(/M) pedestal base adapters feature a 1/4"-20 (M6)-threaded stud that fit into the bottom of our standard Ø1/2" post holders or Ø1" posts to convert them into pedestal-style mounts for added stability. The BE1R(/M) adapter features a magnet in the base that is sufficiently strong to securely hold the base in place without clamping to an optical table (see photo at the top right). Made from solid 303 stainless steel with a 1.25" (31.8 mm) outer diameter, these adapters allow standard Ø1" posts to be used with the clamping forks sold below.

The BE1(/M) base adapter is available in a pack of five for ease of ordering.

Clamping Forks
These clamping forks are designed to provide exceptional clamping force when used with our Ø1/2" post holders and Ø1" posts that have been adapted using the BE1(/M) or BE1R(/M) to pedestal-style mounts. They can also be used with our pedestal-style Ø1/2" post holders or Ø1" pedestal posts without any need for the BE1(/M) or BE1R(/M).

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 0.40" (10.2 mm) long counterbored slots, the CF125 and CF125C(/M) forks offer 1.24" (31.5 mm) long counterbored slots, and the CF175 and CF175C(/M) forks have 1.75" (44.4 mm) long counterbored slots. 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).

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Click for POLARIS-CA1/M Holding Torque Results*
The non-bridging 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.

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The arm can be mounted with either flat surface in contact with the table, allowing for compact setups.

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Side-Located 1/4"-20 (M6) Screw Actuates Clamping Bore

• 3-Point Contact Bore with Flexure Clamping Mechanism
  • Versions for Ø1" or Ø25 mm Posts for Polaris Mounts and Ø1" Monolithic Polaris Mount (See Table Below)
  • 0.60" Bore Depth Supports Height Adjustments Up to 0.25"
  • Allows Posts to be Rotated 360°
• 0.75" (19.1 mm) or 1.30" (33.0 mm) Slot for 1/4"-20 (M6) Cap Screw
• Heat-Treated, Stress-Relieved Stainless Steel Provides Large Clamping Force
• Design Supports Left- and Right-Handed Orientations (See Lower Left Image)
• High Stability Ideal for Use with Our Kinematic Polaris Mirror Mounts
• Vacuum Compatible to 10^-9 Torr at 25 °C with Proper Bake Out
• ±0.001" (±0.02 mm) Surface Flatness

Thorlabs' Non-Bridging 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
vs. Thorlabs' Non-Bridging Clamping Arm

Industry standard clamping forks are designed with a bridge, as shown in Figure 1, for clamping to pedestal-style posts or post holders. This design will slightly damage the laser platform during each use by pulling up the part of the platform located under the bridge. The Thorlabs clamping arm, as shown in Figure 2, is designed with a flat top and bottom to eliminate this problem.

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Figure 1: A Bridge is Created When an Industry Standard Clamping Fork is Used with a Pedestal Post

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Figure 2: The Thorlabs Clamping Arm Eliminates the Bridge Created by an Industry Standard Clamping Fork

The flexure clamp, shown in the photo to the left, is actuated using a side-located 1/4"-20 (M6 x 1.0) cap screw and allows a post to be rotated 360° about its center. As the flexure clamp and mounting slot are secured with separate screws, the position of the fork and the rotational alignment of the post can be adjusted independently. While best performance is achieved with full post engagement, the 0.60" (15.2 mm) thick mounting bore supports up to 0.25" of post height adjustment.

The non-bridging clamping arm design has undergone extensive testing to ensure high-quality performance; see the graph to the upper right. For optimal performance, we recommend tightening the flexure clamping screw of an imperial clamping arm with 15 to 25 in-lb of torque and the flexure clamping screw of a metric clamping arm with 1.75 to 3 N•m of torque. When mounting to a table or platform, we recommend using 40 to 65 in-lb of torque for an imperial clamping arm and 4.75 to 7 N•m of torque for a metric clamping arm. Please note that the values for imperial and metric clamps are not a direct conversion due to an efficiency difference between 1/4"-20 and M6 x 1.0 screws. The efficiency of M6 x 1.0 screws is about 5% less than that of 1/4"-20 screws due to differences in diameter and pitch. For best results, use the maximum recommended torques from each range. These torque values can be dialed in using a torque driver.

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The SPW501 wrench tightens Ø1" posts that have torque slots or holes. 

The SPW501 Spanner Wrench is designed to tighten or loosen Ø1" posts that have torque slots, as illustrated in the photo to the right. The SPW501 can also be used with Ø1/2" posts and Ø1" posts that have through holes. The wrench is designed to fit into the slot or through hole and provide leverage for tightening or loosening the post when mounting the post directly to a tapped hole. Please use minimal force when tightening to prevent binding due to overtightening.