Start with the weight, not the shape

Walk into any working forge and you will see a rack of hammers that looks, at first glance, like a row of near-identical lumps of steel. Spend a week at the anvil and the differences become obvious. The most useful decision you can make is weight, because it governs how much energy you can deliver, how long you can keep working, and how much control you keep over the metal.

A hammer that is too light forces you to swing far harder than you should, which ruins accuracy and tires your shoulder. One that is too heavy does the opposite: you lose control, you catch the edge of the work, and after twenty minutes your forearm is finished. The old rule of thumb still holds up well — choose the heaviest hammer you can swing comfortably for a full session, then take half a pound off.

• 450–700 g (1–1.5 lb) — finishing, small scrolls, light shaping and detail work
• 900 g–1.1 kg (2–2.5 lb) — the general workhorse for most day-to-day forging
• 1.4–1.8 kg (3–4 lb) — heavy drawing out on thick stock, or two-person striking

Most smiths reach for that middle weight for the great majority of their work. If you only ever buy one hammer, make it a 1 kg of sensible proportions.

Face shapes and what they are for

The striking face does the actual work, and its profile decides how the metal moves beneath it. A perfectly flat face can be useful, but it tends to leave sharp edges that mark hot steel. A gentle dome, polished smooth, will move metal cleanly without leaving harsh witness marks.

• Flat or slightly domed face — general forging, flattening and setting down. The all-rounder.
• Fully domed face — planishing and smoothing. Small contact area, so the blows land softly and leave little trace.
• Ball face — riveting, hollow forming and deliberate texturing.
• Rough or textured face — decorative finishes only. Keep one aside for that job and never let it near your finishing work.

Keep your working faces dressed. A few minutes with a file and some abrasive paper, followed by a wipe of oil, will keep a hammer striking true for years.

Peen profiles: the drawing-out workhorses

The peen is the business end for moving metal along its length. A straight-peen runs in line with the handle, so it draws the bar out along its axis as you feed the work forward. A cross-peen sits at right angles to the handle and is handy for spreading metal sideways or drawing out in tighter spots where the handle would otherwise foul the work.

Rounding hammers, common in Swedish and American traditions, combine a domed face with a rounded peen and are wonderfully versatile for general forging and blade work. A diagonal peen, set at about 45 degrees, is more aggressive still and shifts metal quickly when you have a lot of material to move.

The peen edge should be rounded, never sharp. A crisp edge will cut the surface of the steel and leave a line of cold shuts that no amount of subsequent forging will close up properly.

Handle length, grain and grip

Handles generally run between 30 and 40 cm (12–16 inches). A shorter handle gives you more control and a tighter arc, which suits finishing and detail work. A longer one gives more leverage and greater tip speed, which is exactly what you want when you are shifting serious volume on heavy stock — though the extra reach costs you some accuracy.

Look for ash or hickory with the grain running straight down the length of the handle. Run-out, where the grain lines wander towards the edge, is where handles snap. Check the grain before you buy, and check it again every few months for cracks near the eye.

Grip matters as much as geometry. Hold near the end of the handle for full power on heavy drawing out, and choke up towards the head for fine control. Keep the grip relaxed at the top of the swing and let the hammer do the falling — you are guiding it, not forcing it.

Matching the hammer to the job

• Drawing out — a 1–1.4 kg cross-peen or rounding hammer. Brisk, overlapping blows down the length of the bar, rotating the work as you go.
• Flattening and setting down — 900 g–1.4 kg with a flat or gently domed face. Light blows, working in a spiral from the middle outwards.
• Shaping curves and scrolls — 450–900 g, domed face, shorter handle. Control beats power here.
• Punching and drifting — a heavy hammer, 1.4 kg and up, struck squarely with a flat face. Best done with a striker if the work is large.
• Planishing and finishing — the lightest hammer you own with a polished dome.
• Riveting — a 450–700 g ball-peen gives you a rounded head and enough weight to set a rivet in a few blows.

Building a sensible working set

You do not need twenty hammers. Three good ones will carry you a long way: a 1 kg cross-peen for drawing out, a 900 g–1.1 kg flat-faced hammer for general forging, and a lighter 450–700 g domed hammer for finishing. Add a 1.5 kg hammer if you regularly work thick stock, and a ball-peen if you rivet.

Buy fewer, better hammers and look after them. Buy second-hand where you can — old hammers often have better steel than new ones, and a re-dressed face costs nothing but an hour of your time. Set your anvil at knuckle height, stand square to the work, and let the weight of the head do the labour.

The right hammer is simply the one that disappears from your awareness after a few minutes, leaving only the metal, the heat and the sound of the anvil. Get the weight, the face and the handle right, and that is exactly what happens.