1/4"-100 Adjusters

• Five Lengths Available from 1/2" to 2"
• 5/64" (2 mm) Hex Key Compatible
• Max Load: 15 lbs (6.8 kg)
• Material: DFARS-Certified Stainless Steel
  • Traceable Material Certification Available (Must be Requested at Time of Purchase)

Our high-precision 1/4"-100 Fine Hex Adjusters can be adjusted with a 5/64" (2 mm) hex key, F25USK1 removable adjustment knob (sold below), or HKTS-5/64 hex key knob (sold below). The F25US series have a maximum load of 15 lbs (6.8 kg). The adjuster body is constructed of 303 stainless steel and comes pregreased to ensure smooth mating into compatible components. The ball tip is constructed using 440 stainless steel that is fixed onto the adjuster using epoxy.

Drilling and Tapping
While we recommend using our fine adjusters with the appropriately matched threaded bushing (sold below), it is also possible to incorporate them directly into a part or material by creating a threaded hole. For the adjusters on this page, the diameter of the pilot bore should be 0.240" +0.002" / -0.001". The hole can then be tapped with TAP14100. For fine pitch threads, it is especially important to tightly tolerance the pilot bore because of the shallow thread depth. For more information, see our taps and drill bit kit page.

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Coarse Thread Length and Adjuster Length (L)

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A Cross-Section of a Differential Adjuster Screw,
Showing the Internal Components

• 1.02" (26.0 mm) Adjuster Length (L)
• Coarse Thread Length: 0.76" (19.3 mm)
• Fine Adjustment: 25 µm/rev Over ≥400 µm of Travel
• Ø0.49" (12.4 mm), 0.15" (3.8 mm) Thick Locking Ring
• On-Axis Load Capacity: 11.25 lbs (5.1 kg)
• Recommended Preload: 1 to 2 lbs (0.5 to 1 kg)

Thorlabs' DAS25U Differential Adjuster Screw comes pre-greased to ensure smooth mating into compatible components. To install the adjuster, screw the threads into the bushing by hand. Ensure that cross threading does not occur in order to avoid damage to the adjuster and bushing. Additionally, the screw includes a Ø0.49" (Ø12.4 mm), 0.15" (3.8 mm) thick locking ring with a knurled surface for improved grip. Four Ø0.09" (Ø2.3 mm) blind holes in the ring allow a hex key to be inserted to assist with tightening.

When used with a compatible component, coarse adjustment is provided by the external threads on the main screw body, labeled B on the diagram to the lower right. The screw can be actuated using the attached knob, labeled A, or the 5/64" (2 mm) hex socket. The knob can also be removed if needed due to space constraints.

The fine-adjustment mechanism provides a highly de-magnified displacement of 25 µm per revolution and can be actuated using a 1/16" hex accessible through the center of the 5/64" (2 mm) hex for coarse adjustment.

As illustrated in the diagram to the right, an intermediate actuator, labeled C, is threaded into the main body screw (B) and onto a push rod (D) that terminates with a ball tip. A pin on the push rod fits into a slot on the main body screw and prevents these two components from rotating relative to each other. As a result, when the intermediate actuator is rotated, it will be translated along the main body screw at a rate determined by the intermediate actuator's external thread pitch while the push rod is translated in the opposite direction at a rate determined by the intermediate actuator's internal thread pitch. Thus, differential movement is achieved between the intermediate actuator and the push rod.

The DAS25U differential adjuster screw has an intermediate actuator with an external thread pitch of 400 µm and an internal thread pitch of 375 µm. When the intermediate actuator is rotated clockwise, it advances in the main body by 400 µm per revolution. At the same time, the push rod, which is restricted from rotating by the main body, retreats by 375 µm per revolution, providing a total displacement of 25 µm per revolution.

Drilling and Tapping
While we recommend using our fine adjusters with the appropriately matched threaded bushing (sold below), it is also possible to incorporate them directly into a part or material by creating a threaded hole. For the adjusters on this page, the diameter of the pilot bore should be 0.240" +0.002" / -0.001". The hole can then be tapped with TAP14100. For fine pitch threads, it is especially important to tightly tolerance the pilot bore because of the shallow thread depth. For more information, see our taps and drill bit kit page.

• Ideal for Slip Fit
• Two Lengths Available
• Material: 510 Phosphor Bronze (Vacuum Rated for 10^-6 Torr)
• Recommended Bore Diameter: 0.3395" +0.0005"/-0.0000"

Our 1/4"-100 Threaded Bushings are commonly used in slip fit applications where fine adjusters are needed. Due to the tolerances of our fine adjusters, we discourage press fitting these bushings. The recommended bore diameter for our 1/4"-100 bushings is 0.3395" +0.0005"/-0.0000". To learn more about the use of fine adjustment screws and bushings in optomechanical systems, please see the Integration tab above.

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LNR25M Stage Fitted with
F25USA1 Adapter, F25US200 Adjuster, and F25USK1 Knob

• Material: 510 Phosphor Bronze (Vacuum Rated for 10^-6 Torr)
• Adapts 1/4"-100 Adjusters to Ø3/8" Barrel Size
• Recommended Bore Diameter: 0.375" +0.002"/-0.000"

These 1/4"-100 threaded to Ø3/8" barrel adapters are made from 510 Phosphor Bronze (vacuum rated for 10^-6 torr). They allow our 1/4"-100 adjusters to be used with linear translation stages that accept actuators with Ø3/8" (Ø9.5 mm) barrels. The photo to the right shows an adjuster screw used as a replacement for the actuator included with the translation stage. For vacuum applications, we recommend a thorough ultrasonic cleaning to remove any grease or particulates prior to use.

• Knurled Outside Diameter for Easy Tightening
• Material: 510 Phosphor Bronze
• Vacuum Compatibility: 10^-6 Torr

The LN25100 lock nut features a knurled outside diameter, which helps when tightening or loosening the nut. This lock nut is made from 510 Phosphor Bronze, which is vacuum rated for 10^-6 Torr. Each nut features blind holes that allow a hex key to be used to help tighten the lock nut.

• Lock Nut Compatible with the 1/4"-100 Adjusters Sold Above
• Also Compatible with the Adjusters Included on our Polaris Mounts for Ø1" Optics
• Tighten Using a 13 mm Hex Thin-Head or Cone Wrench
• 0.08" (1.9 mm) Thick

The POLARIS-LN1 stainless steel lock nut can be used with any 1/4"-100 adjuster for long-term stability and features a 13 mm hex. This lock nut is compatible with Polaris mounts that have 1/4"-100 adjusters, excluding the piezo-driven mounts, mounts with low-profile adjusters, and vertically driven mounts. The adjuster can be held in place with an adjuster thumbscrew or hex key while lightly tightening the lock nut by hand or with a 13 mm thin-head wrench or cone wrench.

For applications that require frequent tuning of the adjusters, the lock nuts only need to be lightly tightened by hand to a torque of approximately 4 to 8 oz-in (0.03 to 0.06 N·m). For long term stability, we recommend tightening to a torque of 32 oz-in, which can be achieved by using our TW13 preset torque wrench. To avoid cross threading the lock nut, place it against the adjuster and "unscrew" the lock nut until you feel a slight drop; then thread the lock nut onto the adjuster.

Cleanroom and Vacuum Compatibility
This lock nut is compatible with cleanroom and vacuum applications. The lock nut is chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, it is double vacuum bagged to eliminate contamination when transported into a cleanroom.

• Compact Locking Collar: Ø0.33" (Ø8.4 mm), 0.08" (1.9 mm) Thick
• Use One Collar To Lock an Adjuster to a Bushing
• Use Two Collars to Create a Hard Stop on an Adjuster
• Install and Remove with the POLARIS-T2 Spanner Wrench

The POLARIS-LNS1 locking collar is a compact alternative to the lock nut sold above. This locking collar is compatible with all of the 1/4"-100 adjusters sold on this page, as well as those used in many of our mirror mounts and stages. This locking collar is compatible with Polaris mounts that have 1/4"-100 adjusters, excluding the piezo-driven mounts and mounts with low-profile adjusters. Each collar is only 0.08" (1.9 mm) thick and constructed of stainless steel. We recommend the POLARIS-T2 Spanner Wrench to install or remove these locking collars. A center through hole allows a 2 mm ball driver to pass through the spanner wrench, so that the adjuster can be held in position while the locking collar is engaged.

The locking collar can be used to lock an adjuster in a desired position or to create a hard stop at any position to prevent overdriving an adjuster. For applications that require frequent tuning of the adjusters, the locking collar only needs to be lightly tightened to a torque of approximately 4 to 8 oz-in (0.03 to 0.06 N·m). For long term stability, we recommend tightening to a torque of 32 oz-in, which can be achieved by using our TW13 preset torque wrench in combination with the POLARIS-T2 wrench. To avoid cross threading the locking collar, place it against the adjuster and "unscrew" the collar until you feel a slight drop; then thread the collar onto the adjuster.

Cleanroom and Vacuum Compatibility
This locking collar is compatible with cleanroom and vacuum applications. The locking collar is chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, it is double vacuum bagged to eliminate contamination when transported into a cleanroom.

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POLARIS-K1C4 Mount with Optic and Optional POLARIS-N5 Removable Knobs

• For Convenient Adjustment of 1/4"-100 Adjusters
• Attaches Directly to Adjuster Threading
• Sold Individually

The Polaris^® Removable Knobs for 1/4"-100 Adjusters allows the user to adjust a Polaris kinematic mirror mount by hand. The knobs can be used with select Polaris mounts, listed in the table to the right. Note that when the knobs are used with any of these mounts, they will block the side through holes on the adjuster. The adjuster screw's 5/64" (2 mm) hex socket is still usable when the knobs are attached.

The knobs are made from chemically cleaned and heat-treated 303 stainless steel that provides vacuum compatibility down to 10^-9 Torr at 25 °C with proper bake out (10^-5 Torr at 25 °C without bake out).

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F25USK1 and F25USK2 Knobs Shown Attached to a POLARIS-K1E Mirror Mount

• Use with 1/4"-100 Hex Adjusters
• Clearance Hole Allows Access to Hex Socket
• Knurled Knob Increases Adjustment Sensitivity
• Available in 2 Sizes (See Table to the Right)

These removable adjustment knobs are compatible with our 1/4"-100 adjusters, including those used in the Ø1" Polaris Kinematic Mounts. These knobs enable quick and easy tweaking of an actuator without needing a hex key.

We offer two sizes of adjustment knobs. The Ø0.58" standard size (F25USK1) is similar in size to the stainless steel knobs included with our Polaris mount, while the larger Ø0.925" size (F25USK2) provides additional angular resolution.

Please note that these knobs are not compatible with Polaris mounts that use side-hole adjusters. The recessed bore of the knob is not deep enough to allow the knob to engage the threads on the side-hole adjuster.

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POLARIS-K1E2 with HKTS-5/64 Adjuster

• For Convenient Adjustment of 5/64" and 2 mm Hex-Driven Actuators
• Red Anodized Adjustment Knob with Engraved Hex Size
• Replaceable Hex Tip
• Sold in Packages of 4

These 5/64" Hex Key Adjuster Thumbscrews allow for quick adjustment of many 5/64" and 2 mm hex-driven actuators (or standard actuators with the knobs removed). These temporary knobs can be left in the screw's hex socket between adjustments for convenience (see photo to the right). An 8-32 setscrew (5/64" hex) secures the replaceable hex bit, which can be reversed if the tip is stripped. Contact Tech Support to order replacement hex key bits.

We offer hex key thumbscrews in sizes from 0.050" to 3/16" and 2 mm to 5 mm.