Technological process of sleeve, part 5 – boring - MorekTECHTechniki Wytwarzania i Procesy Technologiczne

Technological operation 40 – boring

Figure 1 shows a technological sketch for the technological operation in question – boring a hole. According to the principles of the technical sketch, very thick lines mean surfaces machined in a given technological operation.

Fig.1. The technological process of the sleeve – operation 40 – boring.

Cut No.:	Description of the technological cut:
10	Bore a Ø30H8 hole as shown.

Cut No.:

Description of the technological cut:

Bore a Ø30H8 hole as shown.

We machine on a machine tool called boring machines.

Until now, classical technological literature items treated boring as a rough or shaping operation when used as a machine tool (conventional) lathe. Modernly used numerically controlled lathes (CNC) provide the possibility of obtaining high cutting speeds at low working feeds. In the case of CNC lathes, reamers are not used so commonly, but above all boring bars for accurate machining of holes (with larger diameters and in ductile materials – soft steels for carburizing).

Finishing is accurate hole machining with small depths of cut, below 0.5 mm. This type of machining allows achieving tolerances in IT6-IT8 classes.

Modern tools for boring finishing holes include diameters from 3 to 981.6 [mm] depending on the manufacturer. The depth of the holes subject to finishing boring is 6x the clamping diameter. Within the specified range, the tools have the ability to set the machined diameter to the nearest micrometers.

Finishing boring can be divided into single-edge (IT6-IT8, diameter adjustment on the tool) and multi-edge (IT6, high feeds, large-scale production).

Technological parameters

Cutting speed v_c [mm/min]. The boring bar rotates n rpm machining the specified diameter. The cutting speed has a direct impact on the tool life (cutting insert): \ [v_ {c} = \ frac {\ prod Dn} {1000} \]

Axial feed f_n [mm/rev]. The axial feed speed is the product of the feed per tooth fz by the effective number of inserts (number of cutting inserts machining the surface). Axial feed directly affects surface finish.

Feed speed v_f [mm/min]. Affects productivity.

Material removal efficiency [cm³/min]. The amount of material removed at a given time, which in the case of roughing is related to productivity.

Cutting depth a_p [mm].

Cutting data are also important in terms of machining stability. This is due to chip evacuation and the occurrence of vibrations between the tool and the machined surface. Hence the maximum recommended cutting speed v_c is 240 m/min for finishing. Depending on the tool and inserts selected, the recommended cutting speeds vc may range from 60 to 120 m/min. The maximum recommended cutting depth a_p is 0.5 mm.

Sources

Feld M., Podstawy projektowania procesów technologicznych typowych części maszyn, WNT 2000

Kapiński S., Skawiński P., Sobieszczański, Sobolewski J.Z., Projektowanie technologii maszyn, OWPW2002

Puff T., Technologia budowy maszyn, PWN 1985

Rudaś T., Horczyczak M., Morek R., Materiały dydaktyczne – ZAOiOS WIP PW

Poradnik obróbki skrawaniem, SANDVIK Coromant

http://cnc.pl/porownanie-konwencjonalne-a-cnc.php

https://procestechnologiczny.com.pl/zgrubna-obrobka-otworow/