Making a threading dial

[Mayhem]

I had originally been told that as my leadscrew is 2tpi, I can cut any threads divisible by 2 without using the threading dial, as it will always be in sync. I have cut 12tpi threads this way and it worked but recently I had some issues with 6tpi threads. To test this, I took two consecutive 'scratch' passes and the two did not line up. So I must have been lucky on the 12tpi thread!

So, I decided to use the threading dial but soon discovered a problem: With the half nuts disengaged the dial turns normally. Once the half nuts are engaged the dial stops turning. On closer inspection, the gear on the dial loses contact with the leadscrew once the half nuts engage. I'm unsure why this is????

I have been planning to make a new dial for a while but have no idea where to begin. All the information I have seen is based around 8tpi leadscrews and transposing this to a 2tpi leadscrew doesn't work. The current gear is very roughly cut from some brass plate and some teeth are wider than others. There are no numbers on the dial - only markings are a series of centre punch marks. As such, I have been using only one mark which makes the process rather time consuming.

Any suggestions on how to go about making a new dial? I'm especially interested in being able to correctly stamp numbers on the dial. Of course, I will need to figure out why the dial has stopped rotating.