Geometric chasers

[Winegrower]

Now here is a mystery that I hope the residents here can solve. I have a 9/16” D head, bought a 5/16-18 chaser set from eBay, and it has a weird wrap around thread. They don’t work in my die head. I bought the same description chasers, they are perfect. You can see the two styles…each is marked 5/16-18. Anybody know what’s going on here? The set on the right are correct.

 

[Illinoyance]

I have quite a few 9/16D chasers for sale. What do you need? $20 plus shipping.

 

[OTmachine]

Useful chasers include 1/8" and 1/4" NPT...I see them on eBay occasionally. These are threads that I can't single point thread (can anybody), so they have come in pretty handy.

Taper attachment

 

[Winegrower]

I have quite a few 9/16D chasers for sale. What do you need? $20 plus shipping.

PM sent about this.