It depends on the consular post's appointment availability and on how much of the enterprise's own qualifying evidence already exists. The enterprise package is usually the longer half.
The enterprise file often takes longer than the employee's
Two packages must be ready at once. The employee's own is comparatively quick: citizenship documents, the offer, training certificates and the essential-skills narrative can be assembled in weeks. The enterprise's package is heavier, covering ownership and treaty nationality, the investment, the operating nature of the business, financial statements and its non-marginal character.
If the enterprise has an existing E-2 registration it can be updated; if not, it is being built from scratch and that can take months. Consular appointment availability then sets the outside date and varies by post and season. Plan the machinist's departure from the Asphodel-Norwood employer around an issued visa, not an appointment date, and agree with the American employer what happens to the start date if the schedule slips.
Renewals later depend on the enterprise still qualifying.