GlossaryKind of term: Manufacturing termSingle-point boring
What is single-point boring?
Single-point boring brings a hole to size with an adjustable single-edge tool; the hole follows the spindle axis rather than the pre-drilled hole.
Single-point boring finishes a hole with a boring bar or boring head carrying one cutting edge at an adjustable distance from the centre. On a milling machine or machining centre the boring head turns in the spindle; with a fine boring head the diameter is adjusted in very small steps. Because the hole follows the spindle axis and not the pre-drilled hole, boring can also correct position and straightness, within the stock available. The same work on a lathe is internal turning, usually just called boring.
What limits accuracy in single-point boring?
Achievable size, roundness and finish depend on the stiffness of the boring bar, the ratio of overhang to diameter, the cutting data, the material and the temperature of part and machine. A long, slender bar can deflect or chatter; a damped bar pushes that limit further. For bearing bores in large parts there is the horizontal boring mill, a machine built for this work. Whether position can be corrected depends on the stock: the pre-drilled hole must sit far enough inside the final size for the edge to cut all the way round.
How does single-point boring work in practice?
Boring usually takes longer per hole than reaming: one cutting edge, a low feed for a good wall, and with each new size often a trial cut and a measurement before going to size. That adjustment weighs heavily on a one-off; how much it weighs per piece in a batch depends on how your estimate spreads it. In return you hold a position tolerance between bearing bores, or a size outside the standard reamers, without special tooling. Probing in the machine can shorten the trial cut.
What is single-point boring often confused with?
In English boring is the operation and the result is a hole or bore; in Dutch a boring is the hole itself, which can confuse a quote that passes between the two languages. Nor is boring reaming: a reamer has a fixed size and follows the hole that is already there.
How do you see single-point boring in Blake?
The position tolerance and tolerance class of a bearing bore arrive in Blake as proposals from the drawing, which you confirm or correct. The machining time is labelled as an estimate. If boring takes longer than that estimate, you correct the line with a reason and the previous value is kept. More on estimating.
Frequently asked questions
When do you bore instead of ream?
When the position or straightness of the hole is tight, when no reamer exists at that size, or on large diameters. A reamer follows the pre-drilled hole; a boring head follows the spindle and puts the hole where the program says.
Why does boring take longer than reaming?
A boring head cuts with one edge at a low feed for a smooth wall, and each new size often needs a trial cut, a measurement and an adjustment of the head. Over a batch that adjustment weighs less per piece than on a one-off.