Blacksmith Tong Length Calculator
Calculate blacksmith tong dimensions from stock size and grip type.
Returns rein length, boss width, and jaw depth for flat, bolt, and wolf jaw tongs.
Why tong sizing matters in blacksmithing:
Tong size is a safety question before it is a comfort one. Tongs that are too short put your hands close to the forge and the anvil. Tongs that are too long give you leverage you have to fight, which tires the grip and costs precision.
The jaw opening has to match the stock as well. Loose jaws let the workpiece rotate when you least want it to.
Anatomy of a blacksmith tong:
- Jaws (bits): The gripping end. Must match the stock shape (flat, V-bit, bolt, wolf jaw, etc.)
- Boss (pivot/rivet): The pivot point where the two halves join. Usually 15–25 mm wide.
- Reins (handles): The long handles you grip. The critical length dimension.
Rein length formula: The reins should be long enough that your hand stays at least 30 cm (12 in) from the hottest point of the workpiece. Accounting for jaw length and working distance:
Total tong length = Jaw length + Boss width + Rein length
Where:
- Jaw length ≈ 2–3× the stock thickness (for secure grip)
- Boss width ≈ 20 mm standard
- Rein length = Working distance - Jaw length + Safety margin
Recommended total lengths by forge type:
| Forge Type | Total Tong Length | Rein Length |
|---|---|---|
| Small gas forge | 32–42 cm (13–17 in) | 25–30 cm |
| Medium coal forge | 42–50 cm (17–20 in) | 30–38 cm |
| Large coal forge | 50–60 cm (20–24 in) | 38–48 cm |
| Power hammer work | 55–70 cm (22–28 in) | 42–55 cm |
The rein length is the figure that belongs to the forge. The total is the rein plus the boss plus a jaw sized to your stock, so the totals above assume the stock each of those forges usually holds. Feed the calculator a thin bar and the total lands below the range in its row, which is correct: a short jaw does not need compensating for at the handle end.
Jaw style by stock shape:
| Stock Shape | Jaw Type | Jaw Opening |
|---|---|---|
| Round bar | V-bit or bolt jaw | Stock diameter + 2 mm |
| Square bar | Flat jaw or box jaw | Stock width + 2 mm |
| Flat bar | Flat jaw | Stock thickness + 1 mm |
| Irregular shapes | Wolf jaw (scroll jaw) | Adjustable |
Worked example: Forging 20 mm round bar in a medium coal forge:
- Jaw type: V-bit
- Jaw length: 20 × 2.5 = 50 mm (2 in)
- Boss: 20 mm
- Rein length: 350 mm (14 in) for medium forge
- Total: 50 + 20 + 350 = 420 mm (16.5 in)
- Jaw opening: 22 mm (stock + 2 mm clearance)
Starting stock for making tongs: A general rule: the parent stock for tongs should be 3–4 mm larger than the stock the tongs will hold. For 20 mm round bar tongs, start with 22–25 mm square or round stock, about 40 cm long for each half (rein + jaw from one piece).
Rein spring tip: reins should carry light spring tension when closed on the stock, tight enough to hold it securely without making your hand work to open them again.
A tong ring or clip locks them shut for heavy striking.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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