Compression Lug Die Chart: Die Index Numbers and Color Codes by Conductor Size for 12-Ton Crimpers (Burndy, T&B, Greenlee, Conversions Tech)
Sep 10, 2026
Summary: Compression lugs are crimped with a numbered die that matches the conductor size. The die index number is stamped on the lug barrel and on the die; the color band on the lug matches the color on the die. On 12-ton U-die crimpers the copper index runs from 21 (8 AWG, red) to 115 (1000 kcmil, purple): 8 AWG 21 red, 6 AWG 24 blue, 4 AWG 29 gray, 3 and 2 AWG 33 brown, 1 AWG 37 green, 1/0 42 pink, 2/0 45 black, 3/0 50 orange, 4/0 54 purple, 250 kcmil 62 yellow, 300 kcmil 66 white, 350 kcmil 71 red, 400 kcmil 76 blue, 500 kcmil 80 brown, 600 kcmil 87 green, 750 kcmil 99 black, 1000 kcmil 115 purple. Short-barrel lugs take one crimp; long-barrel lugs take two, three above 500 kcmil. Using the wrong die is the most common cause of a failed pull test or a hot termination.
How to read a compression lug
A UL 486A/B listed compression lug is marked with: the conductor size it fits (for example 4/0 AWG), the die index number to crimp it with (for example 54), a color band matching that die, the number of crimps, and the conductor class it is listed for (Class B, or B through M for flex-rated long barrels). The die index is the Thomas and Betts Color-Keyed system, shared by Burndy, Panduit, Ilsco, Greenlee, NSi and Conversions Tech, so a die from any of them with the same index makes a listed crimp on a lug carrying that index. The finished crimp is embossed with the index number for inspection.
Copper compression lug die chart, 12-ton U-die
| Conductor | Die index | Color | Crimps, short barrel | Crimps, long barrel |
|---|---|---|---|---|
| 8 AWG | 21 | Red | 1 | 2 |
| 6 AWG | 24 | Blue | 1 | 2 |
| 4 AWG | 29 | Gray | 1 | 2 |
| 3 AWG | 33 | Brown | 1 | 2 |
| 2 AWG | 33 | Brown | 1 | 2 |
| 1 AWG | 37 | Green | 1 | 2 |
| 1/0 AWG | 42 | Pink | 1 | 2 |
| 2/0 AWG | 45 | Black | 1 | 2 |
| 3/0 AWG | 50 | Orange | 1 | 2 |
| 4/0 AWG | 54 | Purple | 1 | 2 |
| 250 kcmil | 62 | Yellow | 1 | 2 |
| 300 kcmil | 66 | White | 1 | 2 |
| 350 kcmil | 71 | Red | 1 | 2 |
| 400 kcmil | 76 | Blue | 1 | 2 |
| 500 kcmil | 80 | Brown | 1 | 2 |
| 600 kcmil | 87 | Green | 2 | 3 |
| 700 kcmil | 94 | Pink | 2 | 3 |
| 750 kcmil | 99 | Black | 2 | 3 |
| 800 kcmil | 106 | Orange | 2 | 3 |
| 1000 kcmil | 115 | Purple | 2 | 3 |
Index numbers follow the Thomas and Betts Color-Keyed and Burndy Hydent system used by 12-ton U-die tools; the color sequence repeats every ten sizes, so red is both 8 AWG and 350 kcmil, which is why the number, not the color alone, governs. Always crimp to the index and color stamped on the lug you are holding.
Aluminum and dual-rated compression lug dies
Aluminum conductors use a larger barrel for the same AWG, so a dual-rated AL9CU compression lug carries a different index than a copper lug of the same conductor size, typically the copper index for one to two sizes larger. A 4/0 AWG aluminum lug is crimped with the 250 or 300 kcmil copper die (62 or 66); the lug marking states which. Aluminum barrels are factory-filled with oxide inhibitor and should be crimped without wiping it out.
Crimp sequence
- Strip to the barrel depth marked on the lug plus 1/16 in; do not nick strands.
- Insert the conductor to the inspection hole or the barrel bottom; strands must be visible in the hole.
- Short barrel: one crimp centered on the barrel. Long barrel: first crimp nearest the tongue, second toward the cable end, dies fully closed each time. Rotate 90 degrees between crimps on hex dies.
- Check the die index embossed by the crimp against the lug marking, and confirm there is no flash more than 1/32 in.
- On aluminum, brush the strands and apply inhibitor before insertion; wipe excess after crimping.
What happens with the wrong die
A die one size too large under-compresses the barrel: the strands are not cold-welded, resistance rises, and the termination heats under load; it also fails the UL 486A pull test. A die one size too small over-compresses: the barrel cracks or the strands are cut at the crimp edge, which shows as a broken conductor a few months later. Both are invisible from outside once heat shrink goes on, which is why the die index is embossed into the barrel by the crimp.
Quick answers
Can I use a Burndy die on a Conversions Tech lug? Yes, when the index number and color on the die match the marking on the lug. The index is a shared standard.
What die is 4/0 copper? Index 54, purple, one crimp on a short barrel and two on a long barrel, for 12-ton U-die tools.
What die is 1 AWG copper? Index 37, green. 1/0 is 42 pink, 2/0 is 45 black.
Do battery cable lugs use the same dies? Yes for tinned copper battery lugs; crimp to the index stamped on the lug, which is usually one size larger than the AWG because fine-strand cable has a larger diameter.
Is a dieless crimper acceptable? Only if the lug is listed for dieless crimping; most are listed for a specific die. Check the lug marking and the crimper's listing.
Compression lugs and matching 12-ton die sets are stocked by Conversions Tech, 8 AWG to 1000 kcmil, short and long barrel, one-hole, two-hole and flag, all UL 486A/B listed and marked with die index and color. Selection help: compression vs mechanical lugs; cross-reference by Burndy, T&B or Panduit number at the cross-reference tool.
