No. 4 vs No. 5 Plane

The No. 4 and the No. 5 are the two planes most people meet first, they look almost identical on a shelf, and they do genuinely different jobs. The No. 4 is a smoother, about nine inches long. The No. 5 is a jack, about fourteen. That five-inch difference, plus the way each one is traditionally sharpened, is the whole comparison — and it is enough to make them complementary rather than alternatives.

The specs, side by side

What length actually buys

A longer sole bridges longer hollows, so it corrects a surface toward flat; a shorter sole follows the surface it is given, so it refines rather than flattens. The No. 5 is long enough to start truing a cupped or twisted board, which the No. 4 cannot do — the nine-inch sole simply rides over the dips. The No. 4 is short enough to follow a surface into the last low spots and leave a finish, which is exactly why it is kept short. This is the same length argument that runs all the way up the numbering system, laid out in plane numbers explained.

The camber is half the difference

Most guides stop at length, but the iron shape matters as much. A jack set up for roughing carries a pronounced camber— a curve across the width of the edge — so it takes a deep shaving in the middle and nothing at the corners. That curve is what lets it hog material fast without the corners digging in and leaving tracks. A smoother is sharpened nearly straight, with only the faintest relief at the corners, because its job is a wide, even, whisper-thin shaving. Grind a No. 5 iron straight and it becomes a long smoother; grind a No. 4 iron with heavy camber and it becomes a clumsy jack. The plane number sets the length; the iron you grind sets the personality.

Which to buy first

It depends on where your wood comes from. If you buy surfaced boards and mostly assemble and finish, a No. 4 is the better first plane: it is lighter, more forgiving, and it does the finishing job you actually have. If you dimension your own stock from rough lumber, a No. 5earns its keep first, because there is no substitute for length when a board arrives cupped. And if you are simply learning to use a plane at all, the No. 4 wins on being the easiest thing to control while you build the technique — which is why it heads the ranking on best hand planes for beginners.

Weight and fatigue, in practice

The five-inch length difference comes with a weight difference that matters more than the numbers suggest once you have been at the bench for an hour. A No. 4 is light enough to control with the fingertips and to use through a long finishing session without your forearm complaining. A No. 5 has noticeably more mass, and while that mass is an asset when you want the plane to carry through a cut, it is a liability when you are making dozens of delicate passes. This is part of why the smoother is the finishing plane and the jack is the roughing plane: you want lightness and control for the last passes, heft and momentum for the heavy ones. If you have smaller hands or limited strength, it is a genuine reason to favor the No. 4 first, or even to look at a No. 3, the smaller smoother in the same family described in plane numbers explained.

The one-plane compromise

If budget or space forces a single plane, either can be made to stretch, and the honest answer depends on your stock. A No. 5 with two irons — one cambered for roughing, one straight for smoothing — is the more capable single plane, because its length lets it flatten as well as finish; the compromise is that it is a slightly heavy, slightly long smoother. A No. 4 as your only plane finishes beautifully but cannot flatten a rough or cupped board, so it works only if you buy surfaced stock. Most people who start with one plane and stay with the hobby want the other within a project or two, which is why the two-plane kit keeps reasserting itself.

Feeding them: the sharpening cost is the same

Whichever you buy, the running cost is the edge, not the plane. Both irons are sharpened the same way on the same stones, and both arrive as a ground shape that has to be honed before the plane will cut — the single fact that surprises most first-time buyers. The only difference is the shape you hone: a jack for roughing wants that pronounced camber, a smoother a near-straight edge with the corners just eased. Budget for a stone and a guide alongside either plane, because a sharp mid-price plane beats a dull expensive one every time, and the sharpening kit outlasts the plane. The first-plane version of this argument, with the budget split, is on best hand planes for beginners.

Where they overlap, and where they do not

It helps to be precise about the overlap, because it is real but bounded. Both planes take a fine finishing shaving; both flatten a small, already-near-flat surface; both share the same iron width on the common patterns, so a spare iron can move between them. Where they stop overlapping is at the extremes: only the jack has the length to start truing a rough or cupped board, and only the smoother has the lightness and short sole to chase a surface into its last low spots without effort. Buy for the extreme you actually hit — rough stock means jack, finish-only means smoother — and let the overlap in the middle look after itself.

They are set up differently, not just sharpened differently

Beyond the iron shape, the two planes are tuned for different work at the mouth and the chipbreaker. A smoother is set for its finest possible cut: a tight mouth, the chipbreaker close to the edge to kill tear-out, and the iron barely projecting, so it takes a shaving thin enough to read newsprint through. A jack set up for roughing is the opposite — the mouth opened to pass a thick shaving, the chipbreaker backed off, and the iron advanced for a deep bite.

That is why a single plane set for one job is genuinely mis-set for the other, and it is the practical reason the two-plane kit is more convenient than swapping settings back and forth on one body. If you do run one plane for both roles, expect to reset the mouth and the depth every time you change duty, along with the iron — the full sequence is in how to set up a hand plane. None of it is hard, but it is enough friction that most people who use both roles regularly simply own both planes.

Why most people end up with both

A jack and a smoother is the classic two-plane kit, and it is not a redundancy. The jack takes rough stock down toward flat; the smoother leaves the surface you keep. That pair covers the great majority of furniture work between them, and it is the pairing the ranked list on the best hand planesis built around. If you only ever own two bench planes, these are usually the two. The third, when it comes, is a longer sole for edge-jointing — the step up compared in jack plane vs jointer plane.