CNC Machining Parts Design Guide-Tolerances

CNC Machining Parts Design Guide-Overview
May 23, 2016
CNC Machining Parts Design Guide-Material Selection
June 25, 2016

CNC Machining Parts Design Guide-Tolerances

General Tolerances

If a drawing or specification list has not been provided by the customer, Shank Machining will produce in accord with the specifications listed below:
• For metal parts, tolerance for all dimensions will be +/-0.1mm/0.005”; For plastic parts, tolerance will be +/- 1mm/0.010”.
• The finish will be maximum as Ra3.2/125RMS.
• If tapped holes are not added on the quote and drawings, they will not be added to the part and will be machined in accord with the diameter specified in the model.
• If it is not specifically requested by the customer, no surface treatment (polishing, anodize, powder coat, etc.) will be applied.
CNC Machining tolerance sample picture-Shank Machining-China CNC Machining Supplier

Part Tolerances

According to the the form, fit and function of a part, tolerance is defined by the designer as the acceptable range for a dimension. Unless specifically marked or defined by the customer, the standard tolerance used by Shank is +/-0.1mm/0.005” for metal parts and +/- 1mm/0.010” for plastic parts. If tighter tolerances (less than the standard, e.g. +/-0.05mm/0.002”) are required, the information must be communicated or annotated on the drawings as to which dimensions need a narrow range. For reference, a piece of paper is about 0.07mm/0.003” thick.

It is important to remember that a tighter tolerance will result in additional cost because of increased scrap, additional fixture, special measurement tools and/or longer cycle times caused by the machines. They need to be slowed down to hold the tighter tolerance. Depending on the tighter tolerance and the geometry associated with it, costs could be more than double than holding the standard tolerance.If it is not necessary to use the tight tolerance, It will be better to use the standard one.

Overall geometric tolerances can also be applied to the drawing for the part. Based on the geometric tolerance and type of tolerance applied, additional cost may be the required because of increased inspection times.

To minimize the cost, the best way to apply tolerances is to only apply tight and/ or geometric tolerances to critical areas.

About Shank Machining China:

Shank Precision Machining Parts Co., Ltd was founded in 2005, which is Chinese professional manufacturer of all types of machining parts since 2005, supply quality products at competitive prices. We would like to be your reliable supplier and trusted friends. Thank you for your attention!
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  SHANK PRECISION MACHINING PARTS CO., LTD
Address: No. 88, Lanzhou Rd, Hefei City, Anhui Province, China 
E-mail: info@shankmachining.com
Tel: +86 (0)551 6377 0991
Website: www.shankmachining.com

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