Blacksmith Tong Length Calculator
Calculate the ideal tong length for your stock size and forging style.
Match reins, jaws, and boss dimensions.
Why tong sizing matters in blacksmithing:
Properly sized tongs are essential for safety and control. Tongs that are too short put your hands dangerously close to the forge and anvil. Tongs that are too long create excessive leverage that fatigues your grip and reduces precision. The jaw opening must match the stock size — loose jaws let the workpiece rotate unpredictably.
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 | 35–42 cm (14–17 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 |
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 have light spring tension when closed on the stock — tight enough to hold securely but not so tight that opening them fatigues your hand. A tong ring or clip can lock them for heavy striking.