Boring is a common machining method, which can be used to correct errors. In this guide, we’ll introduce what is boring process and types of machines it uses, as well as the difference between boring and drilling. How to bore holes? 3 machining methods for boring holes for your reference.

What is Boring Process?

Boring is a machining process uses a specially designed cutting tool like a drill bit to enlarge a hole that is already in the part to improve the accuracy. The cutting removes material from the internal of the workpiece. Boring has a wide range of applications, it can machine holes of different sizes and different precision grades. For holes with large diameter, high precision of size and location, boring is almost the only processing method. Boring on the lathe can be completed through mounting the holder and boring tool bar with cutter bit on the tool post and revolving the part.

What is Boring Machine & Types of Boring Machine

Boring machine is an equipment that can produce more accurate and smooth holes through enlarging existing holes which created by drilling or other techniques, it often used to process deep hole in workpieces oil cylinder, cylinder and hydraulic cylinder, or spindle hole, blind hole and step hole of machine tool. There are three boring machines according to the processing:

- Horizontal boring machines: bore holes with a spindle that is parallel to the work table.

- Vertical boring machines: uses a rotating piece attached to a horizontal table, the borer is able to move upwards or downwards.

- Line-boring machines: the boring bar is supported on both ends.

Difference Between Boring and Drilling

1.Function & Purposes

Drilling is to create a hole, while boring is performed to enlarge the hole diameter.

2.Processing sequence

Boring should be executed after drilling.

3.Cutting tool

Drilling uses drill bit while boring uses boring bar. In addition, boring bar is a single point cutter, and drill is based on multi-point.

4.Hole length

Drilling process can increase the axial length of the hole while boring can’t.

5.Chip influence

Chip removal is an issue in drilling, which may make the operation can’t be done continuously, this problem is not exist in boring.

6.Accuracy, Surface smoothness

The surface of drilled parts is rough and edges of the hole may be rugged, but boring can produce accurate sizes, high precision, tight tolerance and smooth finish.

7.Hole diameter

The diameter of the drilled hole is generally the same as that of the drill, so a taper hole can be created. In boring operation, taper holes are easy to get.

3 Ways of Boring - How to Bore Holes 

(1) Workpiece rotates and the cutter feeds, typically operated on the lathe. The center of the hole after machining is consistent with the rotation axis of the machined part, the roundness of the hole is primarily determined by the rotary accuracy of the machine spindle, and the axial geometry error of the hole mainly depends on the position accuracy of the tool feed direction relative to the rotation axis of the workpiece. This boring method is suitable for machining holes with coaxial requirements with the outer circle surface.

(2) The cutting tool is rotating and workpiece feeds. The spindle of the boring machine drives the boring cutter to rotate, and the worktable drives the workpiece to feed.

(3) The cutter rotates and feeds. Applying this boring process, the overhanging length of the boring bar changes, the stress deformation of the boring bar also changes. The hole diameter near the spindle box is larger, and the hole diameter away from the spindle box is smaller, forming a taper hole. In addition, with the increase of the overhanging length of the boring bar, the bending deformation of the spindle caused by the self weight will also increase, and the axis of the hole to be processed will bend. This boring method is only suitable for machining short holes.