On the tension disks, that question was in regards to threading the thread from the top (on the longarm).
So, do I bypass the top tension altogether if I'm using specialty threads... in the top... on the longarm?

Leta Many specialty threads are way too heavy to run through the top which is why some very inventive sewists turned to bobbin work. You can't bypass your tension discs you will end up with some pretty awful stitching if you tried.

I've done a lot of bobbin work on my art quilts. I use my PQ1500s which has the vertical bobbin rather than the drop in bobbin. I've used RazzleDazzle and other thick, lumpy threads that wouldn't go through a needle and it works very well. On the PQ1500s you just use your regular bobbin case and if necessary adjust the tension on the bobbin case, though I've never had to do that. The only thing that can be a little tricky is that you are working with the quilt face down, so you need to come up with some way of orienting yourself. I usually do FMQ when I'm doing bobbin work, but you can also use the regular stitches.

Since I don't use a frame, it's an easy process to switch back and forth from using threads that can go through the needle to doing bobbin work--just a matter of changing bobbins. I keep a quilt sandwich nearby for checking tension when I'm switching between FMQ bobbin work and FMQ with regular threads.

I bought a special bobbin case for the PC420PRW (drop in bobbin), but haven't tried bobbin work with it yet. According to the info that came with that some of the decorative stitches can be used for bobbin work as well

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One way to solve that problem is to quilt it from the top, with water soluble thread in top and bobbin. Then load the specialty thread in the bobbin, regular thread on top, flip the quilt over to the back side, and quilt it again, using your first pass with the soluble thread as a guide. Once the quilt is bound, wash or soak it and the water soluble thread dissolves. :thumbup:

It is really as simple as what Tartan said. You can't put some of these thick designer threads thru the top of your sewing machine but you can put them in a bobbin so you stitch with the back up. I never particular cared for the look.

Great tip, thanks Peckish!
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I've been thinking of doing this myself, as i have done quite a bit on the normal machines- top loading bobbin. I bought an extra bobbin casing (and the latest Brother had one with it) and took the tension screw out, because with thicker threads like crochet cotton, you don't need much tension, and it doesn't muck up the top tension. I will buy another casing for my TL18" quilter.

As mentioned, you will have to expect your designs to be on the back of the loaded fabric. The Innova has a special - and very expensive - foot to do this on top, and I believe it only fits that machine, I may be wrong.
I will be looking for a photo of what you achieve.

I like to couch better, I can never seem to get the tension right.

I have no personal experience with bobbinwork. But would like to mention a very good article, 'Bobbibwork Embroidery' by Gisela Pugni Spätzle, in the latest issue of Threads Magazine, November 2016, # 187. She discusses threads, winding, tension, stitch length and stabilizers for use on DS. I have no affiliation with the magazine.

thank you, I will be on the lookout for this magazine!