Access. With only one upright the working area is open on three sides, so work can be brought in from the front or either side, long stock can pass across the bed, and awkward shapes need not be threaded between columns. On repetitive loading and unloading that saves real time.

The single upright flexes, so the ram and bed stop being quite parallel and the gap widens slightly at full load. That limits achievable accuracy and practical capacity, which is why C-frames are generally rated lower than H-frames of comparable size.

On bush pressing, punching, riveting, staking and general assembly, where a small amount of frame flex has no consequence for the result. For that large class of work the access advantage is free, which is why C-frames are so common in production.

For precision work where ram-to-bed parallelism matters, and for anything approaching the frame's rated capacity, where deflection becomes significant enough to affect the result. Also for heavy straightening, where the loads involved and the need for squareness both point firmly to a closed frame rather than an open one.

Production and fabrication - punching and forming sheet, assembly pressing, riveting and staking - and in bench-mounted form for light component work. The common factor is repeated loading and unloading of parts, where open access shortens every single cycle and those seconds accumulate into real output over a shift.

Usually not - the ram is fixed at the throat of the C, so the work is positioned to the ram rather than the other way round. That is part of why access matters so much on this type: the workpiece must be movable to where the ram is.

The distance from the ram centreline back to the upright, which determines how far into a workpiece the press can reach. It is the dimension that decides whether a given part can be worked at all, and deeper throats flex more, so it trades directly against stiffness.