What is Roughing in Machining – Difference Between Roughing and Finishing | CNCLATHING


Machining is generally carried out in two steps with different cutting parameters and provides varying results. Roughing is usually the first process, which followed by finishing. Go through all the stages, the desired CNC products can be obtained from blanks. In this article, we put the focus on what is roughing in machining, the difference between roughing and finishing.

What is Roughing in Machining?

Roughing operation in machining is mainly used to remove bulk material rapidly and roughly shape the workpiece to the desired form, in order to make the subsequent processing is more convenient and efficient. The purpose of rough machining is to remove the blank allowance quickly, large feed rate and cutting depth are usually selected to remove as many chips as possible in a short time. So rough machined products often get low accuracy, rough surface and high productivity. The roughing process is often the preparation of semi-finishing and finishing.

Why Roughing is Done in Machining? - Advantages of Rough Machining

– Roughing operation can realize fast feed, and the error can be corrected by the following finishing, so as to ensure the quality. 

– Divide the processing stages, the advantages of rough and finish machining equipment can be fully utilized. Roughing equipment has high power, high efficiency and strong rigidity, and finishing equipment has high precision and low error. 

– Rough machining can find various defects of the blanks, such as sand hole, air hole, insufficient machining allowance, etc., which is convenient for timely repair or scrapping, so as not to waste processing time and cost.

– After hot working, the residual stress of the workpiece is large, separate the rough and finish machining, the aging can be arranged to eliminate the residual stress, and finish machining can be arranged to eliminate the deformation after cooling.

– Rough machining is arranged before the mechanical finishing and finishing can protect the surface of different stages from wear.

Roughing vs Finishing - Difference Between Roughing and Finishing

To meet the basic requirement of CNC machining, a number of operations need to be performed in the machine shop, including turning, milling, facing, and more. Conventional machining processes are suitable for high stock removal and good surface quality, which involves two stages or two kinds of processes. The roughing operation is used to produce a part geometry close to the shaped of finished product in a short time, and the finishing operation is performed after roughing to achieve the final geometry and other details. What’s the specific difference between roughing and finishing?

1. Purpose. Roughing is mainly to remove a large amount of excess material from the piece, finishing is to improve surface finish, tolerance, and reduce or minimize the errors. 

2. Parameter. Higher feed rate and cut depth are applied in roughing.  

3. MMR. The material removal rate in roughing process is higher than finishing. 

4. Surface finish. The surface quality after finishing is better than that after roughing. 

5. Precision. Finishing or fine machining can provide high dimensional accuracy and close tolerance while roughing can’t. 

6. Cutting tools. Different levels of roughness make different demands on the inserts and cutting angles. negative rake inserts are best suited for rough machining since they can absorb cutting forces which allows higher cutting speeds. With finish machining, positive rake inserts are usually selected to get a better surface finish.