The rainbow color one looks like metal blue ing, sorry not sure of the spelling lol, when you apply heat to metal. As for the springs on the thread carriage, mine is all home made, i was using the tapered springs and had to modify the carriage to stop the springs from tightening up, then i found some washer type magnets, have been using them for ever now and they work fantastic, smooth and accurate tension every time... Cheers from New Zealand...
The rainbow color one looks like metal blue ing, sorry not sure of the spelling lol, when you apply heat to metal. As for the springs on the thread carriage, mine is all home made, i was using the tapered springs and had to modify the carriage to stop the springs from tightening up, then i found some washer type magnets, have been using them for ever now and they work fantastic, smooth and accurate tension every time... Cheers from New Zealand...