Two types of tensioners to think about. One applies tension to the thread. I dont like this one because it pinches the thread and can cause metallics to seperate
Sewing machine type.
The one that works for me applies tension to the spool itself
Heres how to make your own:
1/4x20 bolt length TBD by you, generally 3".
3 washers
a spring
a wingnut
Assuming you are using some type of rod building jig (wood) you would mount the bolt horizontal.
Slide onto the bolt the following ingredients in this order:
1 washer
Thread spool
1 washer
spring
1 washer
wingnut
Use a little ingenuity to make it fit for your own set up.
Happy turning
Chris