Most people who buy one old Stanley plane end up choosing between these two. The No. 4 is a 9-inch smoother. The No. 5 is a 14-inch jack. Both take a 2-inch iron, both were made from 1869 into the 1980s, and both turn up in big numbers, so the choice comes down to the work you'll give it, not what you can find.
Here's the short version. If you're starting from rough or warped boards and don't own a powered jointer and planer, buy the No. 5. If your boards come off machines already flat and you want to finish them by hand, buy the No. 4.
What the No. 5 does
Patrick Leach, whose Blood and Gore listings are the standard reference on Stanley planes, calls the No. 5 the most useful of all the bench planes and a very good plane to learn on. It's the first plane used on rough stock. With the mouth open and the iron set deep it hogs off wood. With the mouth closed up and a light cut it smooths. It'll even joint an edge, though not as easily as a No. 7 or No. 8.
Christopher Schwarz calls this job the fore plane, and he counts the No. 5 and the No. 6 as fore planes. They take a bowed or cupped board to reasonably flat in a hurry, which is the hardest work in surfacing by hand. For that he grinds a curve into the iron, about an 8-inch radius on his, opens the mouth wide and works diagonally across the board. Jack plane or fore plane, it's the same tool. Old sources, Schwarz says, had carpenters calling it a jack and furniture makers calling it a fore plane.
A No. 5 forgives a lot. A roughing plane doesn't need a dead-flat sole or a surgically sharp edge, and Schwarz rates fore planes the easiest planes to set up and sharpen. His own is an old No. 5 with rusty spots, a homemade tote and a sole of doubtful flatness, and he says it works like a dream. He'd steer a first-time buyer to a used metal No. 5 or No. 6 over a cheap new one or a premium one, and he wants wooden handles, not plastic, because a fore plane gets pushed hard.
What the No. 4 does
The No. 4 is the standard smoothing plane, and Leach credits it and the No. 5 with making Stanley's fortune. It's the fine tool, the last plane to touch the wood before a finish goes on. It takes thin shavings and leaves a surface that needs little or no sanding, and Leach says many woodworkers have their first plane epiphany watching the curls spill out of one.
Smoothers are the fussiest planes to set up. Schwarz wants a very sharp iron with only a hint of curve at the corners, a tight mouth and the cap iron set close to the edge. He also thinks a well-prepared board needs only a little smoothing. That's why the No. 4 suits someone who already has machines. Popular Woodworking's basic kit for new furniture makers starts with a No. 4-sized smoother, a No. 7 jointer and a low-angle block plane, and in Schwarz's own shop the powered jointer and planer do the coarse work, a jointer plane the medium work and the smoother the final pass.
So which one first?
Schwarz frames it as a simple question. If you don't own a powered jointer or planer, the plane to buy at the flea market is a fore plane, which in Stanley numbers means the No. 5. If the only plane you'll own is a smoother, let machines and sanders handle the coarse and medium work and save the No. 4 for the end.
The No. 5 is also the easier plane to get working. It doesn't need a perfect sole or a perfect edge, so it's quicker to get cutting. The No. 4 rewards more setup and sharpening before it does its best work. On the other hand, it's lighter and handier on small parts, and if you mostly build boxes or small pieces from bought, dressed lumber, it's the one you'll reach for most.
Plenty of people end up with both. Leach counts the No. 4, the No. 5 and the No. 7 jointer as the core of most woodworkers' hand-tool kits, so whichever you buy first, the other is likely to follow.
The sizes either side
If a No. 4 feels big in your hand, the 8-inch No. 3 has a 1¾-inch iron, and Schwarz suits the smaller smoothers to narrow work like door stiles and rails. Leach says some people prefer it to the No. 4. The No. 4½ is 10 inches long with a wider 2⅜-inch iron and more weight, for bigger surfaces like tabletops. On the jack side, the 15-inch No. 5½ is wider and heavier, which Leach likes for truing broad panels, and the 18-inch No. 6 is the longer fore plane Stanley advertised as simply a short jointer. Check the iron width on a No. 5½, since it changed from 2¼ to 2⅜ inches in 1939 and Leach says the old width is unique to that plane.
What to check on either one
- Cracks. Look closely at the cheeks and around the mouth in the photos. A crack or a welded repair there is the one fault you can't fix.
- The frog and lateral lever. The lever should be there and the top of the frog unbroken.
- The tote and knob. Tight cracks can be glued, but a sheared-off tote horn or a split knob base means a replacement.
- The iron. Ask how much is left and look for deep pitting near the edge.
- The depth nut. It should turn freely, and mangled knurling means someone forced it with pliers.
- Twist. Ask whether the plane rocks on a flat surface. A little wear on the sole is fine, a twisted body isn't.
Leach warns that thick modern replacement irons sometimes only fit after the mouth is filed wider, which is a change you can't undo. If you can, buy a plane with its original Stanley iron and some length left on it.
Dating the one you find
Both planes follow the Type Study closely, so you can date a No. 4 or No. 5 from a few photos. The patent dates cast behind the frog, the knob height and the lever cap hole get you most of the way, and our Type Study cheat sheet walks through it. When you're ready, the bench plane page and browse show the listings we'd buy right now.
