Wow Preecher, a sewing machine mechanic. I could really do with you down here! Our  industrial machine is  out of action  right now.(It's a phaff) The old thread tension spring broke, so I put a new one in, and everything  seems to have been adjusted to the old chewed up one that finally broke... and  it  has never been the same since.

I use fleece from fabric stores I like it, there is just enough of a pile that you can brush the seams with a stiff hair brush and the seams will not be that visible in the distance that the puppets will be seen. The stretch of the fabric and thickness are important too. I like medium thickness and medium stretch. It is light weight so your puppeteers will appreciate that, fake fur puppets hurt more. It wears well and does not pill much, those little balls that appear when it is worn.  Years ago I found a fabric store going out of business sale with many colors of fleece that was a great find. Fall is the best time to find fleece fabric, after Halloween the prices may go down more. I have a friend who drives to the textile mills in Dallas and California once a year to stock up on cheaper fabric. I found cheaper fabric at a Mill outlet store in the past but now days it is getting harder to find fabric stores. Buying online had been hit or miss for me, the pictures can be deceiving or color off, I like to see and feel the fabric I buy. I wonder if they would send a sample first. I have used old fake fur coats from Goodwill for puppets, that was cheap.

I do NOT recommend felt or Velux for puppet skin, they don't hold up to the stress and your puppet will look bad fast, they are  not worth your time and effort.

Sewing machine mechanics are worth their weight in GOLD! Tension problems are the worst. I can do most sewing with machine, slowly, then use a very long doll needle for hand tacking on hair so that if I want I can remove it later easily. I feel bad sticking that long needle thru the puppets head.

Snail, do you do anything with your hair fiber before tacking it? I make bullion fringe first before sewing it on.

Pages...I cut my teeth on Pfaff sewing machines. What model is it? Is it a home sewer or industrial? I probably can help you with your problem. What exactly is the machine doing? From your post I assume it is a tension problem being you had to change the check spring. Pfaffs are particular as to where the check spring is positioned. It must be around the 11 o'clock position to start with then you can adjust it as needed. It must have enough tension on it to pull the thread around the hook and up to the material to form the proper stitch. You should be able to adjust the tension by sticking a screwdriver in the end of the tension assembly and turning it to the left for less tension and to the right for more tension. If you want to adjust the position of it you must turn the whole assembly by loosening the set screw located at the right hand side of the machine where the tension assembly is located. If you need to take the whole assembly out then loosen the screw enough to pull it out of the machine which you probably are already aware of being you had to change it. If you try to adjust the tension and the whole assembly moves and you see the check spring going up and down then you must tighten the set screw so it won't move. I hope this helped if you need to ask any questions please feel free to do so. 

I would be more than happy to help any others with their machines if they need it. I have about 40 years experience on a wide range of industrial machines and some home sewers as well.

That is so cool that you know so much about sewing machines and are willing to help. A good working machine makes sewing fun instead of frustrating. 

Steven I usually use long Fake Fur that is still attached to the fabric, not individual fibers.  Even Yarn wigs I sew strands to knit fabric base so they are like wigs. I am tacking down that base fabric layer not the loose fibers. That way I can change a young girl puppet to an old grandpa with just a wig and clothes change when the characters change. I am trying to make wefts from acrylic yarn like the doll maker Mozekyto posted not long ago. My first attempt the yarn just broke off so I watched all her videos again, I need to get the pet brush and try again. I love her doll hair wigs she is a master. I may have to sew my wefts rather than glue however.

Snail, I too use long Fur fabric for shorter wigs, but I found weaving bullion fringe made a weft that does not come apart for longer yarn wigs.
Preecher, thanks for the tips. I checked my machine and the tension spring is at  11 o'clock. My machine is a Pfaff 563 industrial. The problem at the moment is it  sews if you go slow enough (which obviously is tricky as it goes like  lightning,) but when I pick up the pace with more speed the thread snaps. It seems sporadic in doing it also. Any advice is appreciated.

So are you making your own bullion fringe from yarn?  I can see how it would be better than loose yarn ends. Have you invented a special took to make your own fringe yet? Opps I see you have and even improved it too, how did I miss those?

Yes Snail , in the 'tools you've made' thread, there are some videos posted. But here they are again:

  for the  loom  to make bullion fringing

   for  repairing broken threads

   for  some improvements

  using store bought fringing.