61.
61.Rough machining method, should take tolerance level what range?
Answer: should take IT10 ~ IT12.
62.Rough boring machining method, should take tolerance level what range?
Answer: should take IT10 ~ IT12.
63.Drilling machining method, should take the tolerance level what range?
Answer: should take IT10 ~ IT13.
64.What is the tolerance level for stamping process?
Answer: should take IT10 ~ IT14.
65.What is the tolerance level for sand mold casting process?
Answer: should take IT14 ~ IT15.
66.What is the tolerance level for metal mold casting process?
Answer: should take IT14 ~ IT15.
67.What range of tolerance should be taken for forging machining methods?
Answer: should take IT15 ~ IT16.
68.Gas cutting machining method, should take tolerance level what range?
Answer: should take IT15 ~ IT18.
69.How many ways are there to determine the fundamental deviation?
A: there are three methods to determine the basic deviation: test method, calculation method and analogy method.
70.What is a test method?
Answer: test method is the method that applies test to decide to satisfy the cooperate kind of product working performance, basically be used at be like aerospace, aviation, national defense, nuclear industry and railroad transportation industry in a few key orgnaization, the important that affects to product performance greatly and lack experience again, crucial cooperate.This method is more reliable.Its disadvantage is the need for testing, high cost, long cycle, less application.
71.What is computation?
Answer: the calculation method is according to the use requirements through the theoretical calculation to determine the type of cooperation.Its advantage is that the theoretical basis is sufficient, the cost is lower than the test method, but because the theoretical calculation is impossible to consider the various practical factors of the working environment of the machine equipment is very comprehensive, so the design scheme is not as accurate as determined by the test method.
For example, when calculating the type of clearance fit of sliding bearing with a calculator algorithm, the minimum allowable clearance can be calculated according to the theory of liquid lubrication, and the appropriate type of clearance can be selected from the standard.Maneuver algorithm is determined completely by the interference of the transfer of load types, according to the size of the load to pass, according to the elastic and plastic deformation theory, the required minimum interference can be calculated, on the basis of choosing appropriate types of interference fit, and checking whether the parts material strength to withstand the cooperate type produced by the greater.
As there are many factors affecting the fit gap and interference, the theoretical calculation can only be approximate.
72.What is analogy?
Answer: analogy method is with the machine that designs a task with same type or the coordination that the mechanism passes production practice to verify to serve as reference namely, combine the actual situation of the use requirement of the product that designs and application condition to decide to cooperate.This method is most widely used, but requires designers to have sufficient reference materials and considerable experience.The following factors should be considered when using the analogy method to determine the fit:
The force.When the force is large, it tends to be too tight to select the fit, that is, the interference amount of interference fit should be appropriately increased, the clearance amount of clearance fit should be reduced, and the transition fit with a large probability of interference should be selected.
Disassembly situation and structural characteristics.To often disassemble assemble cooperate, with the task that does not often disassemble assemble same cooperate, its cooperate should loosen some.The fitting of difficult assembly should also be a little looser.
Combine the length and the configuration error.The longer the fit length is, the tighter the actual fit is compared with the fit with short length due to the shape and position error.Accordingly, appropriate choose proper loose a few cooperate.
Material, temperature.When the materials of phase fittings are different (the difference of linear expansion coefficient is large) and the difference of operating temperature and standard temperature +20 ℃ is large, the influence of thermal deformation should be considered.Effects of assembly deformation.
73.Where is the tolerance grade 5 applied?
Answer: mainly used in the fit tolerance, shape and position tolerance requirements are very small occasions, with stable properties, generally in the machine tool, engine, instrument and other important parts of the application.For example, the box hole matched with class D rolling bearing;Machine tool spindle with e-class rolling bearing, machine tool tail frame and sleeve, precision machinery and high-speed machinery in the journal, precision lead screw diameter.
74.Where is the tolerance grade 6 applied?
Answer: the matching property can achieve a high uniformity, such as the hole and journal matched with the e-class rolling bearing;Shaft diameter connected with gear, worm gear, coupling, belt wheel, CAM, etc., machine tool screw shaft diameter;Rocker arm drill column;The outer diameter size of the guide parts in the jigs;Grade 6 precision gear reference hole, grade 7, grade 8 gear reference shaft.
75.Where is the tolerance grade 7 applied?
Answer: the accuracy of grade 7 is a little lower than that of grade 6, and the application conditions are basically similar to that of grade 6.Such as coupling, belt wheel, CAM aperture;The machine tool clamp disc seat hole, the drill sleeve fixed in the fixture, the drill sleeve can be changed;Grade 7, grade 8 gear reference hole, grade 9, grade 10 gear reference shaft.
76.Where is the tolerance grade 8 applied?
Answer: in the machine manufacture belongs to the medium precision.For example, bearing housing bushing size along the width direction, 9 ~ 12 grade gear reference hole;11-12 grade gear reference shaft.
77.Where is the tolerance level 9 ~ 10?
Answer: it is mainly used for outer diameter and hole of shaft sleeve in mechanical manufacturing.Control parts and shafts;Empty shaft belt wheel and shaft;Single and spline.
78.Where is the tolerance grade 11 ~ 12?
Answer: the match precision is very low, after assembling may produce the very big clearance, is suitable for basically does not have what match the request occasion.Such as machine flange and stop;Sliding speed and sliding gear;Dimension between the processes in processing;Mating parts for stamping processing;Connection of wrench hole and wrench holder in machine tool manufacturing
79.How to choose gap fit in the actual design?
Crane hook hinges, with a tenon flange, internal combustion engine exhaust valve and pipe ↑
Pulley and shaft with internal combustion engine spindle with ↑
Gear shaft sleeve and shaft, drill sleeve and bushing with ↑
80.How to choose transition fit in the actual design?
Lathe tailstock of the top sleeve with wheel and shaft to cooperate with ↑
Rigid coupling with worm wheel bronze rim and spokes with ↑