Tips for your Boring Operation

The lathe is a workhorse in the machine shop. It can perform many rotating operations from threading to facing. Boring on the lathe machine is, in theory, an easy operation, but the precision required calls for close attention to detail.

In manufacturing, boring is the machining process that transforms existing drilled holes or casts. Boring can be applied to increase diameter, enlarge, improve dimensional accuracy, correct deviation of an initial hole, or reduce surface roughness.

Since this is an operation that falls later in the manufacture of a part you want to be certain of accuracy to avoid costly reruns. There are a few common problems that can occur, so these helpful methods and tips for your boring operation will be of great benefit.

Common Challenges of Boring Operations

Tool Wear

During CNC boring operations, the steady cutting of a part can lead to the wear and damage of the machine tool which, in turn, results in reduced precision of the hole boring and heightens surface roughness. Additionally, the calibration of the fine-turning feed becomes irregular, leads to adjustment error, change of machining diameter, and lessens the quality of the product.

Machining Error

Most boring errors are attributed to machining errors. Machining errors can be observed when there has been an alteration to the dimension, shape, position and/or surface quality of the part. Some common machining errors include:

The blade material is not suited for the part material.
The parameter of boring is incorrect.
The offset of the original hole position allows for minor changes of the allowance.
The material of the part has low plasticity or high rigidity.
The distribution of allowance adjustment is unrealistic.
The length-to-diameter ratio of the cutter rod is too big, or the overhang is too long.

Surface Quality

Rather than a smooth finish, the machined surface of boring parts displays thread-like or fish scale cutting lines.

Adjustment Error

Incorrect input in the altering of the distribution feed allowance creates the likelihood of low accuracy.

Measurement Error

Incorrect measurements and use of measuring tools are common quality assurance errors in CNC boring processes.

Tips and Procedures to Overcome Boring Challenges

Machine Setup

Make sure the workpiece positioning, clamping, and working holding are secured before machining.
Ensure the spindle repeated positioning is correct and the dynamic balance accuracy is suitable to the requirements of CNC machining.
Observe the dynamic gravity overhang value of the boring bar at the trial stage of the boring process and slightly alter the cutting parameter to limit the impact of vibration.
During the boring machining process, the machine should be kept at a low temperature with increased lubrication to decrease the cutting force, as needed.
Remove chips, as required, and prevent the chips from engaging in the second cutting.
Examine the tool wear regularly and change the damaged cutter immediately to safeguard the quality and precision of the hole boring.

Tolerances

Use a caliper to measure the diameter of the original hole and calculate the reserved machining allowance.
Depending on whether the operation is rough boring, semi-finished boring, or finished boring, practically allot the boring allowance. (We recommend the following: 0.5mm for rough boring, 0.15mm for semi-finished and finished boring.)
Incorporate good boring processes for hard-to-machine materials and precision boring, the boring allowance should not be lower than 0.05mm.

Boring Tool Tips

Once the boring bar is mounted, examine if the upper plane of the main tool edge of the boring tool is aligned with the feed direction of the boring tool head and on the same horizontal plane. This ensures that the cutting edges are in the normal machine cutting position.

Trial Boring Tips

The boring tool should set aside an allowance between 0.3-0.5mm when expanding a bore, but change the allowance of rough boring to ≤0.5mm to ensure that the following finish boring machining can achieve the allowance demands.

Machining of any nature requires precision, and boring is no exception. The process must consider boring bar selection, set up, cutting edge geometry, tool deflection, lubrication, cutting parameters, chip evacuation, the temperature of the part, and your ability to measure the bore precisely. When it comes to ensuring the best possible results, these tips for your boring operations help create a critical process for every aspect of the procedure.