AnthonyG

Hmm. It seems like I spoke too soon. My lastest set of tests were done with the grain of the webbing, where I was able to get a tension setting adjusted properly. The first set of tests in my original post were done cross-grain to the webbing. I tested some different types of webbing and was able to get tension set no problem. I think it's just the particular type of green webbing I've chosen is very stiff in the one direction. I'm going to try a larger needle and report back soon.

I followed your advice and adjusted the bobbin case opener. This seems to have solved the problem which is great, but it has also made me aware of something else: At higher tension settings I noticed the little release hook on the bobbin case is holding on to the needle thread and creating a small snap. I'm referring to the little hook I circled in red. When the needle thread tightens up to make the stitch I'm noticing the thread is getting held up by this little hook until the bobbin spins around far enough to fully release the thread. I don't notice it so much when I'm sewing light material, but at higher tension settings, and slower speeds this produces a fairly audible crunching noise/snapping noise, and also causes the check spring to jerk back and forth. See the two videos I attached. Edit: I realize it's a bit hard to see since I'm using black thread, but you can hear the check spring bouncing back at 0:10 and 0:23 The check spring snaps back at the point when the thread is released from that little hook.

Edit: Just took a look, and I think you may have solved my problem! The bobbin case opener is adjusted such that it is too far away and not engaging with the bobbin case, leaving it to float freely. What is happening, is the needle thread is getting caught up around the tab. When I go slowly it's even causing some snapping in the check spring which I did not notice before. It's late now, so I will follow your video and give this an adjustment tomorrow!

By calibrate I'm referring to the little pin and plate behind the tension unit that control the release of the tension disks. When I got the new tension assembly I had to bend the plate a bit to ensure the pin was engaged in the lifted position. Pics I took for reference: The tension works fine on lighter materials. I'm not working on any leather at the moment, but it appears to be fine on both Canvas and 500D Nylon. edit: this is the exact thread I am using: http://www.thethreadexchange.com/miva/merchant.mvc?Screen=PROD&Product_Code=BNL069GREO04Ba I apologize if any of my terminology is incorrect. I'm brand new to industrial machines, and learning as I go.

Thanks for the tips. 1. I just re-tested the tension with your suggested threading direction. While I found it resulted in a bit more tension, the results remain the same 2. I threaded the machine with the disks open and made sure the thread was seated properly. 3. Yes, I get tension when I pull the thread after the second disk. 4. Yes, the top post is threaded:

I'm trying to sew 2 layers of 1" nylon webbing and am getting the top thread showing on the bottom regardless of how tight I set the top tension; See images attached. The black thread is topside, green thread is bottom side. Both threads are size 69 bonded nylon. In the image of the bottom side I've tightened the top tension a little bit each time, until the final row where I maxed-out the tension. As you can see there is virtually no difference. I've tried two different needle types with the same results: Organ DP x 17 125/20 and Groz-beckert 110/18 RG. The organ needle is the largest one I currently have, and should be adequate for the size of thread I'm using. I'm wondering if the type of webbing I'm using requires a specific size or needle point? Things I've tried with no improvement on the bottom side stitches: Increased top tension all the way Reduced bottom tension to almost nothing Re-timed my machine Removed and cleaned the bobbin case/assembly I will also add, the tension unit is brand new, but I did take the time to calibrate it so tension engages and disengages properly with the knee lift. Images of the tension assembly attached. Is there something special about setting up this machine that I've overlooked? Any recommendations on things to try would be greatly appreciated.