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What metal parts tolerances can you achieve?

Writer: KangDing hardware Pubdate:2017-09-01 Source:CNC Machining Factory
Description:A very common questions we are asked is: What tolerances can you generally achieve?. However, giving out a-one-tolerance-fits-all answer would be unrealistic and too far away from manufacturing reality. Nevertheless we would like to give you...

A very common questions we are asked is: “What tolerances can you generally achieve?”. However, giving out a-one-tolerance-fits-all answer would be unrealistic and too far away from manufacturing reality. Nevertheless we would like to give you a rough idea about tolerances.

Tolerances depend on numerous influencing factors such as

   The size of the part
    
Parts use
    
product design
    
Quantity, type and size
    
3D surface
    
Use material
    
Surface treatment



For that reason our engineers and technicians will need to carefully review each individual design. You will then be advised if we can or cannot achieve your desired tolerances and how you may need to alter the design to achieve your desired tolerances. If you have particular tolerance requirements, please feel free to get in touch with us today.

Below, please also find some further information on tolerances:

Stamping parts dimensional accuracy of the grade requirements and surface roughness of the grade requirements, is the national standard in the concept of recommendation, in Kangding, we according to the production of product requirements and practical needs (The preparation of non-tolerance standards and requirements), or use the national standard tolerance value (usually IT14 level). The surface roughness grade is directly mounted to the drawings will be denoted by, usually the surface roughness of the stamping parts is not required,
Its requirements are mainly reflected in the raw materials, when the steel plate is ordered, the surface material of the surface roughness range is selected, or when the parts of the surface roughness requirements are more stringent, may rely on raw materials can not guarantee, then follow-up will add some other technology: polishing, plating and so on.

basic size Hole class H14 Shafts h14 Non-porous shaft JS14
above To Tolerance zone
  3 +0.25
 0
 0
-0.25 
±0.125
3 6 +0.30
 0
0
-0.30 
±0.15
6 10 +0.36
 0
 0
-0.36
±0.18
10 18 +0.43
 0
 0
-0.43
±0.215
18 30 +0.52
 0
 0
-0.52
±0.26
30 50 +0.62
 0
 0
-0.62
±0.31
50 80 +0.74
 0
 0
-0.74
±0.37
80 120 +0.87
 0
 0
-0.87
±0.435
120 180 +1.00
 0
 0
-1.00
±0.50
180 250 +1.15
 0
 0
-1.15
±0.575


Metal powder casting depends mainly on the tolerance of the main model, so the general application of the tolerance of +/- 0.15%. This depends on the part geometry. To ensure accuracy of the metal member, it will typically cause the mold, the heat treatment jig. This ensures that the parts do not shrink when the heat treatment.

Metal powder casting  
CT
Datum size Tolerance level CT
4 5 6 7 8 9 10 11 12 13 14
Tolerance values mm
0~10 0.26 0.36 0.52 0.74 1 1.5 2 2.8 4.2  
10~16 0.28 0.38 0.54 0.78 1.1 1.6 2.2 3 4.4
16~25 0.3 0.42 0.58 0.82 1.2 1.7 2.4 3.2 4.6 6 8
25~40 0.32 0.46 0.64 0.9 1.3 1.8 2.6 3.6 5 7 9
40~63 0.36 0.5 0.7 1 1.4 2 2.8 4 5.6 8 10
63~100 0.4 0.56 0.78 1.1 1.6 2.2 3.2 4.4 6 9 11
100~160 0.44 0.62 0.88 1.2 1.8 2.5 3.6 5 7 10 12
160~250 0.5 0.7 1 1.4 2 2.8 4 5.6 8 11 14
250~400 0.56 0.78 1.1 1.6 2.2 3.2 4.4 6.2 9 12 16
400~630 0.64 0.9 1.2 1.8 2.6 3.6 5 7 10 14 18
630~1000   1 1.4 2 2.8 4 6 8 11 16 20
1000~1600   1.6 2.2 3.2 4.6 7 9 13 18 23
1600~2500   2.6 3.8 5.4 8 10 15 21 26
                    General tolerances for length dimensions


Our general tolerances for CNC machining of metals is DIN-2768-1-fine and for plastics DIN-2768-1-medium.  Tolerances are greatly affected by wall thicknesses, material choice, and geometry, so we will seek to advise as to achievable tolerances for each part.  We pride ourselves on wishing to help our clients achieve their desired tolerances that are better than DIN-2768-1, but we work on a “best effort basis only” if the tolerances stated are tighter than our stated standards.  The reason we refuse to be held accountable for very tighter tolerances is that we are a prototype factory and very tight tolerances present a huge risk due to the nature of our work.
 DIN ISO 2768-1 
Nominal size Tolerance size
Range  f (fine  m (intermediate  c (Crude  v (Very thick
 mm  Tolerance  mm  Tolerance mm  Tolerance mm  Tolerance mm 
 0.5-3  ± 0.05   ± 0.10   ± 0.15   - 
 3- 6  ± 0.05   ± 0.10   ± 0.20   ± 0.50 
 6- 30  ± 0.10   ± 0.20   ± 0.50   ± 1.00 
 30- 120  ± 0.15   ± 0.30   ± 0.80   ± 1.50 
 120- 400  ± 0.20   ± 0.50   ± 1.20   ± 2.50 
 400- 1000  ± 0.30   ± 0.80   ± 2.00   ± 4.00 
 1000- 2000  ± 0.50   ± 1.20   ± 3.00   ± 6.00 
 2000- 4000  -   ± 2.00   ± 4.00   ± 8.00 

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