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CleanTop Optical Breadboards

  • Overview +

    CleanTop® steel optical breadboards provide exceptional rigidity and damping for smaller tops. Available in both 2 and 4 inch thicknesses, these tops have the same high-performance CleanTop structure as our large optical tables.

    Three performance levels available, as well as a large variety of customization options.

    • 78 Series
      Provides the ultimate in rigidity and damping for smaller tops. Recommended for the most demanding breadboard applications.
    • 77 Series
      Slightly thinner top skin than 78 series resulting in slightly lower rigidity and damping but at lower cost and weight.
    • 75 Lightweight Series
      Minimizes both weight and cost. These breadboards have relatively high levels of rigidity, as they utilize our standard steel core, however, with their thin top and bottom skins, they cannot have the rigidity and damping properties of the 78 and 77 series. They are ideal when light loads are anticipated and low weight and/or cost are the most crucial factors. The weight savings – 50% less than the 78 Series Breadboard.


    Our steel breadboards can be readily designed to meet custom requirements including custom mounting hole patterns, through-holes, special shapes and custom materials.

    75 series steel optical breadboard

    75 Lightweight Series Optical Breadboard


  • The CleanTop Advantage +

    All steel construction. No particle board sidewalls or plastic layer between top skin and honeycomb core. Assures maximum strength and structural integrity

    Smallest core cell size, highest core density. The CleanTop design does not require enlarging the steel honeycomb core cell size because CleanTop cups are cylindrical, not conical as found in plastic layer designs. CleanTop's average cell size of 0.5 in.(2) is at least 50% smaller than that achieved with plastic layer designs assuring the highest stiffness and greatest core-to-skin bonding contact area

    Steel to steel to steel. CleanTop achieves a spill-proof core with only two bonding layers: top skin to core and core to bottom skin. Imitations must add a third bonding layer which weakens the structure: top skin to plastic layer, plastic layer to core, and core to bottom skin.

    Thermal stability. The CleanTop all steel construction assures materials of identical coefficient of thermal expansion ensuring optimal thermal stability. 

    TMC's CleanTop Optical Top is the best method yet for providing a spill-proof, clean, precise, and corrosion resistant optical top with unmatched structural performance. CleanTop is now a standard feature of all TMC optical tops.

    Individual CleanTop cups are epoxy-bonded under each tapped hole after it is tapped and cleaned. Cups are made from chemically resistant nylon 6, and stainless steel (304 alloy) cups are available. Holes are now tapped and countersunk prior to adding the cups to allow the machined top sheet to be thoroughly cleaned with open, rather than blind, holes prior to bonding. The top plate is processed through a custom TMC industrial cleaning center where a high pressure, high temperature cleaning solution is forced through each threaded hole, completely clearing any machining or tapping debris. Several rinse and dry cycles ensure an essentially "sterilized" top surface prior to bonding the cups.

    CleanTop represents another innovation in TMC's long optical top tradition of industry "firsts" including:

    • First spill-proof optical top (CleanTop) 
    • First all-steel optical top 
    • First oil-free optical top 
    • First honeycomb core registered  to the tapped hole array
    • First lightweight breadboard with formed rather than drilled holes
    • First vacuum compatible optical top
    • Liquid spills on the surface are contained and cannot reach the top's honeycomb core.
    • The core is completely clean and dry with no residual thread-cutting oils to out-gas.
    • Extremely clean tapped holes make screw insertion smooth and simple.
    • Easy retrieval of small parts dropped into the holes is assured.
    • Since no penetration of the core is possible when dangerous chemicals are used on the top's surface, health hazards will not occur by chemicals reaching the core unnoticed. 
  • 20 Reasons for Choosing TMC CleanTop® Optical Tops +

    TMC CleanTop®


    Competitive Construction


    TMC: Formed Steel Sidewalls

    Other: Particle board sidewalls

    TMC: Steel-to-steel bonding throughout 


    Other: Weak plastic layer separates core and top skin

    TMC: High stiffness, small cell size core, individual nylon cups

    Other: Less rigid, large cell size core; molded plastic cups

    1. Sidewalls of TMC tops are 0.075 in. (2 mm) thick, damped, cold-rolled formed steel (see center photo, above), unlike the moisture-absorbing particle board favored by other manufacturers, presumably for its low cost. In addition, steel provides structural integrity unattainable with particle board sidewalls.

    2.TMC’s design does not require enlarging core cell size because CleanTop cups are cylindrical, not conical like molded plastic membrane cavities. Our average cell size of 0.5 in.2 (3 cm2) is at least 50% smaller than molded cavity top designs, assuring the highest stiffness and greatest core-to-skin bonding contact area.

    3. CleanTop achieves a spillproof core with only two bonding layers: top skin to core and core to bottom skin. Imitations must add a third bonding layer, which severely weakens the structure: top skin to plastic layer, plastic layer to core, and core to bottom skin.

    4. Additionally, to avoid excessive epoxy being squeezed into the plastic cups, imitative designs use only the thinnest layer of epoxy between the top skin and plastic layer. The thinness of this layer can produce “voids” when the top is bonded by trapping air, significantly weakening the bond.

    5. TMC employs a proprietary process to clean our machined skins to a level that is virtually “sterilized.” This ensures the cleanest threaded holes and superb epoxy bonding. Furthermore, the cleaning station is in an entranceway to a clean, finishing building so that the cleaned top never sees a heavy, industrial machining environment. In the CleanTop® design, no machining, grinding or sanding of any kind is performed subsequent to this cleaning process.

    6. TMC top skins are stretcher-leveled, stress-relieved, and pressure-bonded against a precision-lapped granite plate, without subsequent grinding—avoiding heat and stress. The finished top is flat within ±0.005 in. (0.13 mm) within the entire tapped hole pattern, regardless of top size, guaranteed.

    TMC top skin (above) and competitive design top skin (below) after grinding.


    7. Top surfaces of TMC tops are lightly sanded with an orbital pattern to remove burrs and provide a non-glare, non-reflecting finish, without inducing internal stress.

    TMC no-glare surface (above). Ground surface of competitive design creates reflection and glare (below).

    8. Standard mounting holes in TMC tops are tapped, either 1/4–20 on 1 in. centers or M6 on 25 mm centers. Imperial 1/4-20 tapped holes on 1 in. staggered centers and metric M6 on 25mm staggered centers are available at a nominal additional fee. Custom patterns, including large through-holes for cables, etc., are easily accomplished with our multiple 2,000-watt laser machining centers.

    9. All TMC mounting holes are in register with open cells in the honeycomb core (a given with CleanTop® but not necessarily with other designs). This assures that the core is not damaged by subsequent drilling and tapping during manufacture, that the structural integrity of the assembly is maintained, and that all mounting screws can be inserted to full depth without obstruction.

    TMC registered holes (shown without CleanTop® cups.) (top), Competitive non-registered holes (bottom).

    10. Every hole in a TMC top is lead-screw-tapped, the most precise method known, and there are no inserts. Inserts can loosen, and top skins can be distorted when inserts are pressed into undersized holes.

    TMC countersunk holes (above) versus non-countersunk holes in competitive design (below)

    11. TMC mounting holes are slightly countersunk to remove ridges and burrs. Every TMC mounting screw can be finger-tightened at first insertion – no wrench is needed. 

    12. TMC’s broadband dry damping approach is the only logical one for an optical top. Others use "tuned" dampers which only work on a discrete frequency. Structural resonances are not discrete and therefore not eliminated but rather "split" into two resonances by tuned dampers.

    13. TMC’s honeycomb core is made of 0.010 in. (0.25 mm) thick steel, work-hardened and plated to prevent corrosion and assure years of service. Steel honeycomb is the ideal material for optical tops since the Young’s modulus of steel is three times that of aluminum.

    14. TMC’s honeycomb core is a closed-cell structure with basic cell size of 0.5 in.2 (3 cm2), giving a core density of 13-14 lbs/ft3 (300 kg/m3), significantly greater than others on the market. The effective core density is 18-20 (16 lbs./ft3) including sidewalls and dampers.

    TMC's honeycomb core. 


    18. Structural damping of TMC tops is accomplished using broadband mass dampers which are separate from the core, do not permit hysteresis or creep of the top, and do not detract from the top’s stiffness. 

    19.Our unique, direct core-to-top bonding improves the thermal conductivity of the core to the outside environment, reducing the "thermal relaxation time" for the top.

    20. Our skins, core, sidewalls and dampers are all made of steel and therefore have the same coefficient of thermal expansion. Thus, even in situations with repeated temperature cycling, a TMC top expands and contracts as a whole, assuring structural integrity and preventing long-term internal stress buildup.

  • Specifications +

    • Core: Steel honeycomb, closed cell, 0.01 in. (0.2 mm) thick foil
    • Core shear modulus: 275,000 PSI (19300 kg/cm2)
    • Core cell size: < 0.5 in.2 (3 cm2)
    • Core density: 13.3 lb/ft3 (230 kg/m3)
    • Flatness: +/-0.005 in. (0.13 mm)
    • Top skin: 430 series ferromagnetic stainless steel
    • Top skin thickness: 3/16 in. (5 mm) for 78 series. 1/8 in. (3 mm) for 77 series. 0.075 in. (2 mm) for 75 series
    • Sidewalls: Damped formed steel channel covered with vinyl
    • Tapped holes: Backed by 1 in. (25 mm) long CleanTop nylon cups.

  • Accessories and Options +

  • Application Photos +

  • Ordering Information +

    You can now request a quote for CleanTop optical breadboards via our Online Product Configurator.

    TMC offers a wide variety of standard CleanTop sizes and thicknesses. Custom configurations are available upon request.

    77 & 78 Series   Standard Width
    12 in.
    (300 mm)
    20 in.
    (500 mm)
    24 in.
    (600 mm)
    30 in.
    (750 mm)
    36 in.
    (900 mm)
    40 in.
    (1000 mm)
    48 in.
    (1200 mm)
    12 in. (300 mm) - - - - - -
    24 in. (600 mm) - - - - -
    30 in. (750 mm) - - - - -
    36 in. (900 mm) - - -
    40 in. (1000 mm) - - - -
    48 in. (1200 mm) - -
    60 in. (1500 mm) - -
    72 in. (1800 mm) - -
    80 in. (2000 mm) - - - - - -
    96 in. (2400 mm) - - -
     75 Series  Standard Width
    19 in.
    (450 mm)
    23 in.
    (600 mm)
    35 in.
    (900 mm)
    23 in. (600 mm) -
    35 in. (900 mm) - -
    47 in. (1200 mm)
    78 77 75
    Skin Thickness 0.188 in. (5 mm)
    0.125 in. (3 mm) 0.075 in. (2 mm)
    2 in. (50 mm) 4 in. (100 mm) 2 in. (50 mm) 4 in. (100 mm)  2 in. (50 mm)
    0.135 lb/in.2
    (10 g/cm2)
    0.195 lb/in.2
    (14 g/cm2)
    0.100 lb/in.2
    (7 g/cm2)
    0.150 lb/in.2
    (11 g/cm2)
    0.070 lb/in.2
    (5 g/cm2)
    Standard Hole Pattern Options 
    (no holes)
    1/4-20 holes
    1" centers 
    M6 holes
    25 mm centers
    Imperial Double Density™
    Staggered 1/4-20 holes
    1" centers
     Metric Double Density™
    Staggered M6 holes
    25 mm centers
    Support systems are ordered separately. See the Support Systems page.