5.7. Smooth gauges and their tolerances
5.7.1. Classification of calibers
In mass and large-scale production, the validity of parts with a tolerance of/T6-/TІ7 is checked with the help of limit gauges. The caliber is a control device that reproduces the geometric parameters of the elements of the product, defined by the specified limiting linear or angular dimensions, and is in contact with the product element over surfaces, lines or points. Limit is the caliber reproducing the limits of the maximum /> min) and the minimum (
Types of calibers (GOST 27284-87) are distinguished:
- in the form of working surfaces: smooth, conical, threaded, keyed, splined, profile;
- for the purpose: through, pass-through, element-wise, integrated, working, receiving, control, installation, sorting, to measure the depth (height), ledge;
- according to the design features: gauge-plug, caliper-gauge, caliber-ring, caliber-bush, unregulated, adjustable, full, incomplete, single-ended, two-way (one-sided, two-sided).
A smooth gauge is a caliber with a smooth working surface (cylindrical, spherical, tapered or flat).
A plug gauge, which is a caliber with an outer cylindrical or conical surface, serves to control the holes.
The caliper (with the working surfaces located on the inner input of the bracket) serves to control the shafts. The set of working limit gauges for the control of the dimensions of smooth cylindrical parts consists of a passing gauge PR, which controls the limiting size corresponding to the maximum permissible amount of the material of the product (Unip, a * ^), and the non-flowing HE gauge, which controls the limiting size corresponding to the minimum allowable quantity of the article material 0
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Receiving gauges serve for the control of products by the customer.
Control calibers (counterclimbers) are designed to control the size of the working calibrated passage (K-PR) and non-flow (K-HE) during their manufacture (they are pass-through, so the lightly lubricated smoothly enter the appropriate workable bracket under the action of its own mass ), as well as for monitoring wear (K-I) pass-through calipers during their operation (they are non-conductive). This is due to the fact that during operation the caliper-brace can easily be damaged, and its control by universal means is difficult. Counterclimbers perform in the form of washers. The gauge plug is easily verified by universal measuring instruments, therefore it is not provided for countercampibers. In small-scale production, it is advisable to use end measures of length or universal measuring instruments instead of counterbalibris. The mounting calibers are designed for the installation of adjustable gauges and measuring instruments.
Shafts and holes with tolerances that are more precise than grade 6 are not recommended to be checked with calibers, since a large measurement error is introduced. Such products are checked by universal means.
Structurally gauges manufactured odnopredelnymi either containing only one passage or through passage gauge (e.g., kontrkalibry) or dvuhpredelnymi (bilateral) whose pass-go gauges and are located on opposite sides. Sometimes dvuhpredelnye gauges are manufactured as one-sided, t. E. Of such caliber communicating and impassable side are arranged one after the other.
Caliber-plugs consist of pens and inserts (or nozzles), which are their working elements, but are structurally performed in different ways. For holes up to 50 mm they are made in the form of full stoppers, 50-100 mm - full and incomplete plugs, over 100 mm - only incomplete plugs. For larger sizes (over 360 mm), instead of stoppers, we use internal gauges.
Caliber staples are also of different types. Preferred one-sided limit brackets (sheet, stamped and cast), as more economical. To control the quality of products 8 and more coarsely find the use of adjustable staples (with plug-in and mobile jaws), which make it possible to compensate for wear, and also be adjusted to different sizes.
The calibers are made of instrumental carbon, alloyed structural or cemented steels, followed by hardening of 62-65 hardnesses. To increase the durability of the calibers wear-resistant coatings are used, for example, chromium plating, or they are equipped with a hard alloy, which provides a significant increase in wear resistance (up to 150 times) with a slight increase in production costs (2-5 times).
When constructing limit gauges, it is necessary that the principle of similarity (Taylor's principle) be fulfilled: the passing gauge must have the form of a controlled part, since it controls the deviation of the size and shape of the part being checked; the non-moving gauge must have a point contact with the component being checked, since it controls only the dimensional deviation.
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Limit calibers allow you to simultaneously control the dimensions and deviations of the shape of the part and check whether the deviations in the dimensions and shape of the surfaces of the parts are within the tolerances field. The product is considered fit if the errors in size, shape and location of the surfaces are within the tolerance range.
On the diagrams shown (Figures 5.49 and 5.50) the following designations are accepted: Д ^ and - respectively the largest and the smallest dimensions of the product; IT-product tolerance; I-allow new calibers for the hole (except calibers with spherical measuring surfaces); Hs - tolerance of calibers with spherical measuring surfaces; I, - admission of new calibers for the shaft; Нр - tolerance of control calibers for staples; Z- deviation of the middle of the tolerance field of the passing plug-gauge II with respect to the smallest limiting size of the monitored hole; Z, - the deviation of the middle of the tolerance field of the gauge ring-gauge I or caliber-bracket (view 2) with respect to the largest limit dimension
Fig. 5.49. Arrangement of the margins for the tolerances of the limiting gauges for holes (a) and shafts (b) for dimensions up to 180 mm:
1 - the tolerance field of the product; 2 - tolerance of working caliber; 3 - control caliber tolerance field
controlled shaft; K-admissible yield of the size of the worn-out passage gauge-plug 11 beyond the margin of the product's tolerance field; Vt is the permissible yield of the size of the worn-out gauged caliber ring I or the caliber of the clamp (form 2); a, a. - the amount of compensation is inaccurate
Fig. 5.50. Arrangement of the margins for the tolerances of the limiting gauges for holes (a) and shafts (b) for dimensions over 180 mm:
1 - the tolerance field of the product; 2- tolerance field of working caliber; 3 - control caliber tolerance field
Control of calibres, respectively, holes or shafts with dimensions over 180 mm.
Schematic representation of calibers and their names, taking into account the design of the calibers, are given in Table. 5.35.
The numbers and the names of certain types of smooth unregulated gauges for monitoring holes with nominal diameters from 1 to 500 mm and shafts with nominal diameters from 1 to 315 mm, as well as individual types of control gauges for calipers-staples are given in Table. 5.36.
5.35. Schematic view of calipers
5.36. Unregulated gauges for monitoring holes and shafts
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