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Slotted Bases![]()
BA1V Vacuum Compatible BA2 BA1S RSPCS Swiveling Position Retainer BA2F Flexure Clamping Mechanism BA2T2 Adjustable Base BA2L Base with 6-32 and 8-32 Taps BA1R Magnetic Base Related Items ![]() Please Wait ![]() Click to Enlarge Components Mounted on BA2 Bases
![]() Click to Enlarge LDM90 Laser Diode Mount on a BA2L Base ![]() Post Holder and Base Assembly Features
The bases found on this page have a universal design that allows them to be used with imperial or metric components, such as post holders. However, it is best to use a metric base with a metric optical breadboard and an imperial base with an imperial breadboard. By matching metric with metric and imperial with imperial, the bases can be positioned flush against each other without leaving unused rows of holes, as shown in the image to the right. For more information on the differences between Thorlabs' imperial and metric components, please see our imperial vs. metric tutorial. Standard Bases Vacuum-Compatible Bases Bases with Tapped Mounting Holes Magnetic Bases Adjustable Bases Flexure Bases ![]() Click to Enlarge UBP2 Universal Base Plate In addition to the advantages stated above, using these bases to directly mount a post will also remove the issue of table flexing, or bridging, that is commonly seen when using standard clamping forks. Please click here for more information on the detrimental effects of table flexing. Universal Base Plate Swivel Base Adapter Base Position Retainers
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 and equipment.
Washers: Using Them with Optomech![]() Click to Enlarge Figure 2: Install washers before inserting bolts into slots to protect the slot from damage. The rounded, smooth side of the washer should be placed against the slot, and the rough, flat side should be in contact with the bolt head. The smooth surface is designed to translate easily across the anodized surface, without harming it. The BA2 base is illustrated. ![]() Click to Enlarge Figure 1: The diameter of the washer is 35% larger than that of the bolt head. This results in over a six fold increase in overlap area with the slot of a BA2 base. By distributing the force of the bolt over a larger area, the washer help prevent gouging of the slot. The head of a standard cap screw is not much larger than the major diameter of the thread (Figure 1). For example, a 1/4"-20 screw has a head diameter between 0.365" and 0.375" and the clearance hole diameter for the threads is 0.264". When the screw is tightened directly through the clearance hole to secure the device, the force is applied to the edge of the through hole, often cutting into the material (Figure 1). Once the material is permanently deformed, the screw head will want to fall back into the gouged groove, thereby moving the device back to that location when attempting to make fine adjustments. A device with a circular through hole is not meant to translate around the screw thread so the deformation is not expected to be a problem. However, a slot should provide the ability to secure the device anywhere along the length for the lifetime of the part. Using a washer distributes the force away from the slot edge to decrease the chance of deforming the slot and extending the lifetime of the part. Figure 1 illustrates the difference a washer can make. The contact area between the slot of a BA2 base and a 0.27" diameter cap screw is 0.010 in2. When a 0.5" diameter washer is used the contact area is 0.064 in2, which is over six times larger. When using a Thorlabs washer, there are two distinct sides (Figure 2). One side is flat and rough and the other is curved and polished. The curved and polished side should be placed against the device, which has an anodized surface. As the screw tightens, the screw head can force the washer to spin against the anodized coating. If the flat side is pressed down against the anodization, the friction created by the rough flat side can scratch the anodized aluminum. However, if the curved side is facing down, the smooth surface has less friction leading to less scratches and extending the visual appearance of the device. Date of Last Edit: Dec. 4, 2019
Bases: For Stability Orient the Side with the Undercut DownAn undercut is machined into the bottom surface of bases like the BA2 (Figures 3 and 4). The undercut creates feet, which are called pads. For maximum stability, the base should be oriented with its pads in contact with the table or breadboard. The top surface of the base does not have an undercut and is the intended mounting surface for components. Mounting the base upside down could result in the base rocking on the table or breadboard, or the base may exhibit other mechanical instability. The Pads are Flatter than the Top Surface Friction heats the pads during the processing step that provides them with a maximally flat profile. By reducing the surface area of the pads, the undercut reduces the amount of heat generated during this step. It is beneficial to minimize the heat generated during machining. Metal expands when heated, and the uneven heating that occurs during machining can distort the dimensions of the part. If the dimensions of the part are distorted during machining, the part can be left with high spots and other undesirable features after it cools. This can cause instability and misalignment when using the part. Precision Instruments and Devices have Pads ![]() Click to Enlarge Figure 5: Pads machined into Thorlabs' devices improve their stability when bolted in place. The pads are highly flat and project above the undercut region, which is highlighted red. The undercut limits the contact area with the table or breadboard. ![]() Click to Enlarge Figure 4: This view of the bottom shows the undercut highlighted in red. By removing this material, the pads can be made maximally flat. ![]() Click to Enlarge Figure 3: For optimal stability, the base should be mounted with the undercut facing the optical table or breadboard. Date of Last Edit: Dec. 9, 2019
![]() ![]() Click to Enlarge The height of any component mounted on a BA2(/M) base can be increased in increments from 0.010" (0.25 mm) to 2" (50 mm) using a mounting base spacer. ![]() Click to Enlarge Post Holder with Lens Mounted on BA1L Base
Thorlabs offers a variety of standard anodized aluminum bases to best utilize space on an optical breadboard. For close positioning of components, our BA1S(/M) base features the smallest footprint, while the BA1SL(/M) base offers a longer slot length for flexibility. For increased stability while maintaining a small footprint, the two-slotted BA1(/M) is a good option. For the greatest stability, consider our BA2(/M) and BA3(/M) bases, which offer a larger contact area. The BA2(/M) features two straight slots, while the BA3(/M) has two radial slots for 90° of manual rotation. As our longest standard base, the BA1L(/M) provides 1.44" (36.6 mm) of lateral positioning and can be secured to an optical breadboard by two screws, even when oriented at varying angles with respect to the tapped hole pattern (see photo to the right). Please note that a 3/8" long, 1/4"-20 (10 mm long, M6) cap screw is recommended for attaching post holders to our standard mounting bases. To reduce packaging waste, we offer our most popular sizes in packs of five. ![]()
These vacuum-compatible bases are constructed from 6061-T6 aluminum and are chemically cleaned and prepared for vacuum applications before packaging. They are compatible directly out of the packaging with vacuum environments down to 10-6 Torr. With additional cleaning and processing, they can be used at even lower pressures, only limited by the outgassing rate of the aluminum, which is 7.6 x 10-9 Torr-Liters/s/cm2 at 20 °C. The material properties of the 6061-T6 aluminum and the cleaning methods that are completed by the end user should be used to determine the appropriateness of these products and materials in a specific vacuum system operating at pressures under 10-6 Torr. These bases are packaged in double airtight bags for cleanroom and vacuum chamber applications. A 3/8" (10 mm) long 1/4"-20 (M6) vented cap screw (SH25S038V or SH6MS10V, respectively) is recommended for attaching post holders to our mounting bases. We also offer additional vacuum-compatible Ø1/2" post system components. ![]() ![]() Click to Enlarge 2" Beamsplitter Cube Mounted on BA4 Mounting Base Using a PM4 Clamping Arm
These mounting bases offer a larger mounting surface than our standard bases and an array of tapped and counterbored mounting holes. These features make it possible to mout larger components or small optical systems. Each base has nine counterbored mounting holes for 1/4"-20 (M6) cap screws. 6-32 (M4) taps compatible with our clamping arms allow these bases to be used as base plates for large prisms and beamsplitter cubes. The BA4(/M) also features ten 1/4"-20 (M6) taps for mounting optomechanics. The imperial versions of each size also have two 8-32 tapped holes for additional versatility. Please note that a 3/8" long, 1/4"-20 (10 mm long, M6) cap screw is recommended for attaching post holders to these mounting bases. ![]()
These anodized aluminum magnetic bases are modeled after our popular standard bases but are enhanced by bottom-mounted rare earth magnets, which provide the ability to temporarily secure components during the setup process. The force from these magnets is strong enough to help prevent accidental movement of components, while still allowing for easy repositioning. The full functionality of these bases can only be achieved when using them on a magnetic table or breadboard; however, they can function as a standard base on non-magnetic surfaces as well. Each base attaches to a post holder via cap screws that fit within a bottom-located 1/4" (M6) counterbored hole. For final attachment to an optical breadboard, each base features at least one slot for a 1/4"-20 (M6) cap screw. Once positioning is complete, these bases must be screwed down to be permanently secured to the table. The BA1SR provides one 1.10" (27.9 mm) slot and allows for the smallest footprint. For increased stability while maintaining a small footprint, the BA1R provides two 0.81" (20.1 mm) slots. Finally, for the most support, the BA2R features two 1.25" (31.8 mm) slots. In addition, the BA2R comes with four bottom-located M3 counterbored holes for 34 mm rail mounting. ![]()
The anodized aluminum BA2T2(/M) complements our popular line of standard mounting bases. It features a 1" (25.4 mm) long, counterbored slot along the center length that contains a 1/4"-20 (M6) threaded stud ideal for use with our Ø1/2" post holders. This slot provides for two-dimensional positioning of any attached optical component. To reposition a post holder on the base, loosen it by rotating it counter-clockwise, slide it into the desired position, and retighten it to the base. The base also contains two 1/4"-20 (M6) counterbored holes located on either side of the 1" long slot. The BA2T2 is shown on the right with a Ø1/2" post holder, a Ø1/2" post, and a KM100 Ø1" mirror mount. ![]() ![]() Click for Details BA2F Base for Ø1" (Ø25.0 mm) Posts Mechanical Drawing (Click Here for the Metric BA2F/M Drawing) ![]() Click for Details BA2E Base for Ø1/2" (Ø12.7 mm) Posts Mechanical Drawing (Click Here for the Metric BA2E/M Drawing) ![]() Click to Enlarge Steel Insert Prevents Damage to Flexure Mechanism by Limiting Overall Travel
![]() Click to Enlarge When Used with a Screw the 8-32 (M4) Tap Acts as a Rotational Stop These mounting bases contain a central double bore and non-marring flexure clamping mechanism that allows for the mounting of Ø1/2" (Ø12.7 mm) posts, Ø1/2" post holders, or Ø1" (Ø25.0 mm) posts. The flexure clamp is actuated by a side-located 3/8"-24 (M10 x 1.5) setscrew and 3/16" (5 mm) hex key. A permanent steel insert at the end of the flexing mechanism, shown to the left, acts as a hard stop and prevents damage to the clamp from over tightening. The double bore that goes through the part allows a post to be mounted within the base and in direct contact to the optical table surface. Standard bases have the post or post holder mounted directly on their surface which will inherently increase the minimum optical axis height and make the system less stable*. The method of mounting also removes the need for intermediary parts, such as a post holder, when mounting a post. The height of the mounted post can be stably raised by 6.0 mm (0.24") within the Ø1/2" (Ø12.7 mm) double bore of the BA2E(/M) and by 7.0 mm (0.28") within the Ø1" (Ø25.0 mm) double bore of the BA2F(/M). The use of an R2 or R2T post collar with the BA2E(/M) or an RM1A or RM1B collar with the BA2F(/M) will create a hard stop for repeatable height adjustments. Each mount also contains an 8-32 (M4) tapped hole next to the double bore. With a cap screw or setscrew inserted into this hole, the post collars can also be used as a rotational stop, as shown for the BA2E in the image to the right. Each base has two 1.25" (31.8 mm) long counterbored slots for 1/4"-20 (M6) cap screws for attachment to an optical table or breadboard. Please see the mechanical drawings to the above right for details. Please note that the flexure mechanism for the BA2F will contact the steel insert when mounting Ø1/2" post holders, since they are slightly smaller in diameter than Ø1" posts. This is normal operation and will not harm the mounting base. If a Japanese post standard (Ø12.0 mm) needs to be used with the BA2E(/M), an AD12BA barrel adapter will be needed to bridge the 0.7 mm (0.03") gap between the post and flexure arm. The flexure arm will not be able to contact the smaller post diameter without this. *A stability test was performed with a Ø1/2" (Ø12.7 mm) post mounted in a BA2E so that the post was in contact with the optical table. This was compared with a post mounted via a cap screw to our standard BA2 base. A 20 in-lb force was applied perpendicular to the post axis in both cases and the deflection of the post was recorded. Upon completion, the post within the BA2E had an overall deflection from center of about 0.001", while the post on the BA2 had a deflection from center of 0.002". ![]() ![]() Click to Enlarge Centrally Located Slot Allows Mounting of Components Outside of the Standard 1" Hole Pattern ![]() Click for Details Mechanical Drawing
The UBP2(/M) Universal Base Plate increases the flexibility of any optical setup by providing mounting holes in virtually any orientation on an optical table or breadboard. This freedom allows users to mount various components or stages in a wide array of orientations outside of what is dictated by the standard 1" (25 mm) hole pattern. The counterbores in the plate also allow one to adapt metric components to an imperial optical table and vice versa. The plate dimensions are 2.5" x 2.5" x 3/8" or 65 mm x 65 mm x 10 mm for the metric version. The 1.25" (31.8 mm) long counterbored slot for 1/4"- (M6) cap screws is centrally located and allows 360° rotation of the plate as well as rough translation on the optical table. An array of 1/4"-20 (M6) and 8-32 (M4) tapped mounting holes are available for mounting components in various orientations, while four 4-40 tapped holes are spaced for compatibility with our 30 mm cage system. Two counterbored holes for both 1/4" (M6) and #8 (M4) cap screws are also located on both sides of the base plate for mounting optical post assemblies. The counterbored holes for 1/4" (M6) cap screws are located in two corners on each side of the plate and are diagonally across from one another. The counterbored holes for #8 (M4) cap screws are located on the center line perpendicular to the counterbored slot with a spacing of 2" (50.0 mm) on the top of the plate and 1" (25.0 mm) on the bottom of the plate. Please see the mechanical drawing above for more details. Please note that these plates are not machined with relief cuts like the other plates shown on this page. ![]()
Our 360° swivel base adapter fits standard Ø1/2" post holders with 1/4"-20 (M6) mounting holes and minimizes the amount of time it takes to assemble an optical system. In addition, the swivel design is ideal for applications that require a large number of components to be packed into a small area. When our Ø1/2" post holders are used with this adapter, the combination is nearly that of our very popular Universal Post Holders. This anodized aluminum adapter has the benefit of compatibility with any of our existing Ø1/2" post holders but does not offer the same height flexibility of the swiveling post holders, which allow the post to be lowered all the way to the table. For ease of ordering, these base adapters are also available in packs of five. ![]()
Thorlabs' Position Retainers can be used to realign bases and other squared-off components 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 component from your setup. The three white dots engraved on the surface of the retainer mark the three points that contact your part. The two dots near the ends of the outer arms can also be used independently as contacts for posts. For more information on using our anodized aluminum retainers with a post, click here. The RSPCS(/M) Swivel Retainer features a swivel head for 200° of rotational adjustment. This enables users to save the arbitrary position and angular rotation of squared-off optomechanical components. To achieve this, the component should be independently locked before aligning the three dots on the RSPCS(/M) to the corner of the component. Partially loosen the tension adjuster screw and then mount the retainer to a breadboard tap while maintaining contact with all three points. 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. The RSPC Fixed Retainer is a compact solution for situations where a tapped hole is diagonally positioned from the base, as shown in the second photo below. As with the RSPCS, the component should be independently locked before aligning the RSPC retainer. After the retainer is mounted in place, the component can be removed from the setup and then later placed back into the same position. The RSPC Retainer can also be secured to an optical table or breadboard via the CL6 clamp. This clamp is useful in situations where the RSPC cannot be placed directly over a hole in the table. ![]() Click to Enlarge RSPCS Swiveling Position Retainer | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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