Granite precision parts


Coordinate measuring machines "Made in Germany" by THOME Präzision




Overview granite precision parts



Material properties of granite

Material properties of granite


Custom-made products from granite

Custom-made products from granite


Measuring bars made of granite

Measuring bars made of granite



Angle standards from granite

Angle standards from granite


Measuring plates from granite

Measuring plates from granite


Cubes from granite

Cubes
from granite



Material properties of granite


Thread inserts in granite

Thread inserts are glued into the granite

Very large granite measuring plate

Very large granite measuring plate

Cubes of granite

Steel insets can be glued into precision granite parts as required

Round granite measuring plate

Round granite measuring plate - Ideal for use as round table top

Granite - A modern material for high-precision parts

High-precision components can be ideally manufactured in granite. The reasons for this are primarily the extremely good properties of this material. Natural hard stone is the ideal basis for the manufacture of precision products due to its fine crystalline structure, low coefficient of expansion, high abrasion resistance, optimum vibration damping and freedom from unwanted internal stresses. Very fine surface quality can be achieved when machining hard stone. This makes granite parts particularly suitable for air-bearing guides. The air consumption is reduced to a minimum due to the high surface quality. In any case, the use of granite is always worthwhile when the quantities of parts, such as machine beds or high-precision base plates for guides, are relatively small. If the quantities are over 50 per year, the use of polymer concrete can be considered. We can also make you an offer for polymer concrete. However, please note the high initial costs due to the production of the mould.


Comparison of the material properties of granite and competing materials like polymer concrete or cast iron

Property Unit Granite Polymer concrete Steel Cast Iron
density kg/dm³ 2,9 2,1 - 2,4 7,85 7,15
Bending Strength N/mm² 13 25 - 35 300 - 600 290
Compressive strength N/mm² 250 100 - 180 260 - 1200 720 - 1150
Linear expansion µm/(m°K) 5 - 7 12 - 20 12 10
Thermal conductivity W/(m°K) 3,0 1,3 - 2,0 50 50
Special heat capacity J/(kg°K) 845 900 - 1100 500 500
Modulus of elasticity kN/mm² 60 - 90 30 - 40 210 88 - 113

In addition to the properties shown in Table 1, there are other advantages to using hard stone:

  • Vickers hardness 850-900 (harder than steel)
  • low linear coefficient of expansion
  • the specific weight is comparable to that of aluminum
  • the elasticity comparable to that of cast iron
  • no burr formation
  • non-magnetic
  • tension-free
  • not conductive

  • Background information on granite

    Magmatic rocks are formed by cooling hot molten material from the earth's interior, the so-called magma. If the cooling takes place underground, one speaks of plutonites or intrusive rocks. Due to the relatively good thermal insulation of the overlying rocks, the molten magma cools down only slowly so that large mineral crystals can be formed. Examples of plutonic rocks are granite or gabbro. The magma can form huge rock masses, the so-called plutons, which often contain several thousand cubic kilometers of rock Granites (from Ital. granito, "granulated") are massive, relatively coarse-crystalline, magmatic deep rocks (plutonites), which are rich in quartz and feldspars, but also contain dark minerals, for example mica. The phrase feldspar, quartz and mica, the three I never forget, gives a somewhat simplified description of the composition of granite. Translated with www.DeepL.com/Translator (free version)




    Custom-made products from granite



    Custom-made from granite

    Custom-made from granite

    Custom-made from granite

    Custom-made from granite

    Today, high-precision granite parts are widely used. They can be found in circuit board drilling machines, measuring machines, grinding machines, milling machines and other applications. Granite can be machined particularly accurately. Up to under 0.001 mm/m is possible. The surface quality is extremely good. This makes it possible to realize very precise guides in combination with air bearings. But granite is also frequently used as a basis for recirculating ball bearing guides. The execution in hard stone is especially worthwhile if only small quantities with high precision are needed. The granite components are finished in very precisely air-conditioned rooms. When machining, it is very important that you give us the support points on which the part is supported during installation. This is the only way to achieve the highest, repeatable accuracy. Translated with www.DeepL.com/Translator (free version)

    The final inspection is carried out with laser interferometers, autocollimation telescopes and electronic inclination scales of highest precision. According to your specifications, we insert appropriate threaded holes, T-slots or various metal parts into the granite body. We work with a high-strength two-component adhesive specially designed for bonding steel / granite. Below you will find a table with the dimensions and the maximum permissible tightening torques for the standard threaded inserts. The positioning accuracy of the threaded hole is +/-0.1 mm. The inserts are inserted approx. 0.5 - 1 mm below the surface.







    Measuring bar of granite according to DIN 874


    Measuring bar of granite

    Measuring bar of granite, hollow bored

    Granite measuring bar with box

    Granite measuring bar with box

    With the measuring bars made of granite, the main focus is on the parallelism of the longitudinal surfaces to each other. They serve as straightness standards. The underlying standard for the granite measuring bars is DIN 874 for parallelism. Mainly granite measuring bars are used for straightness and parallelism control of guides and for alignment purposes. The granite measuring bars are designed as follows:

    Dark hard stone, the two narrow longitudinal surfaces are lapped parallel to each other, all other surfaces of the measuring bars are cleanly ground, two handling holes are drilled at each of the besselsche contact points. The delivery takes place in a wooden case.

    We can also produce higher accuracies on request. Here you see only an extract of our delivery program. Also handling drillings and other special requests can be realized. In special design THOME Präzision can also supply measuring bars with 4 longitudinal surfaces lapped parallel and at right angles to each other. Please ask for all special requests individually.


    Measuring bars made of granite in the store Shop Messmaschienen THOME Präzision




    Angle standards from granite


    Angular normal rectangular shape made of granite

    Rectangular angle standard in granite

    Angular normal triangular shape made of granite

    Triangular angle standard made of granite

    Granite angles in square and rectangular form for checking and adjusting squareness according to DIN 875

    Hard rock angle standards are primarily used to control the 90° angle. Angle standards are ideally suited for quick alignment of angles (for example for measuring machines or machine tools). The granite angle standards are made of dark hard stone. Four narrow surfaces of the angle standards are parallel to each other and lapped at right angles. The specification of the angular accuracy is related to the long leg. The two large surfaces of the granite angle standards are ground. Through-holes are provided for weight reduction and better handling. Threaded inserts for eyebolts can also be provided on request. The underlying standard of our granite angle standards is DIN 875 for rectangularity. A wooden case and a test report are included in the delivery.


    Granite angle standard in triangular shape according to DIN 875

    These granite angle standards are used to control 90° angles. They are made of dark hard stone. The two narrow leg surfaces of the granite angle standards are lapped at right angles to each other, the remaining surfaces are cleanly ground. The angular accuracy is related to the longer leg. Through holes are drilled to reduce weight and for better handling. The underlying standard for our granite angles is DIN 875 for rectangularity. A wooden case and a test report are included in the delivery.

    Angle standards from granite in the store Shop Messmaschienen THOME Präzision




    Cubes of granite


    Granite cubes from granite

    Granite cubes from granite

    Ideal for quickly checking all geometries

    These hard stone cubes are used as angle standards. The angle check is time-saving and extremely accurate. Granite cubes are used in machine tools and measuring machines for fast geometry checking. The granite cubes are made of dark hard stone. All 6 sides are lapped at right angles to each other, the opposite sides are parallel. The angular accuracy is related to the longer leg. To reduce weight and for better handling, through holes or threaded inserts can be inserted according to customer requirements. The underlying standard for the granite cubes is DIN 875 for rectangularity. A wooden case and a test report are included in the delivery.

    Granite cubes in the store Shop CMM THOME Präzision




    Measuring plates of granite


    Granite measuring plate with base

    Granite measuring plate with base

    Granite measuring plate

    Granite measuring plate with base

    Measuring plates made of granite serve as a basis for control, assembly and laboratory purposes. The granite measuring plates are made of black hard stone (granite). The surface of the granite measuring plates is first finely ground and then lapped. The sides of the granite measuring plates are cleanly ground. The granite measuring plates are chamfered on the reverse side. The flatness of the measuring plates is classified according to DIN 876. The granite measuring plates serve as measuring tables in combination with a base frame.


    Setting up a granite measuring plate


    The flatness of a granite measuring plate is only guaranteed if it is installed correctly. Please proceed as follows:

  • Place the measuring plate on the three marked support points
  • Level the measuring plate by adjusting the three support points (set horizontally)
  • Level the measuring plate by adjusting the three support points (set horizontally)

  • All standard measuring plates from THOME Präzision have the same support points as besselsche support points. The support points with the lowest deflection are located about 22% from the edge.

    Granite measuring plates in the store Shop CMM THOME Präzision







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    Coordinate measuring machines from THOME Präzision in use

    Scanning of free-form surfaces with the portal measuring machine RAPID-Plus
    The hand-held measuring machine SMART measures a milled part with holes and distances



    CNC coordinate measuring machine RAPID-Plus

    Measuring range from 500/700/500 to 800 / 1,500 / 700

    3D measuring machine TETA

    Measuring range: from 900 / 1,200 / 800 to 1,100 / 2,200 / 1,000

    Hand-held CMM SMART

    Measuring range from 600/400/300 to 800/600/300