TABLE OF CONTENTS Rotary unscrewing is used where split line witness cannot be tolerated or often when larger numbers of impressions are required.
There are many different ways of automatically unscrewing threaded parts, which will be discussed in more depth later. The basic method for rotary unscrewing is either to unscrew the part from the core or to unscrew the core from the part. Figure 13.10 shows a typical basic arrangement.
Rotating cores or cavities can be actuated by a rack-and-pinion system, with a rotating core or with a rotating cavity.
Collapsible cores are in wide use for producing thread forms and justifiably so. Collapsible coring has the following advantages and disadvantages:
Available as a standard unit.
Available in a reasonable range of sizes.
Undercut forms up to 5 mm are possible.
Ease of location into tool.
Cost-effective for small numbers of impressions.
Limited thread length.
Expensive for larger numbers of impressions.
Can require frequent maintenance.
Cooling the cores can be difficult.
