Dies for SCT machines are now (2019) duplex. They can be rotated for a second life and then flipped for an entirely new tooling face. This increases die life. For most users, no die replacement will be necessary. For those giving their machines intensive use, we estimate the current dies can deliver in excess of 200,ooo threadings.
When a die set is badly worn, its surface will feel rough. Close examination shows material has fractured and broken away. The metal does not wear down. It eventually fatigues and crumbles. Even when the wear is advanced, good spoke threads can be made as, in flat die rolling, the spoke rotates six times so the die has many chances to form a correct thread.
Adjusting your machine to have moderate thread depth will help dies last longer. Rather than going to ISO/JIS spec (2.27mm thread OD on 14G) stay a bit below this (2.20mm). Oversized spokes (2.0+ wire diameter) come around and we don’t want your machine to be under excess pressure. That will wear dies.
Always best to use oil when threading and brush out the dies after a few runs. Any oil will do and rag or brush is effective. Use stuff that’s sustainable and smells good.
We now recommend that all bicycle spoke gauges be rolled with this primary die set: 15, 14, 13, 12G. Simply adjust the shimming of the dies as explained on page 8 of the Operation Manual, available to download here.