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ChapinLeather

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Posts posted by ChapinLeather

  3. Posted · Report reply

    Debbie, I can help you fix this. First, find the metric hex drive wrenches that came with your Cobra 4. You will need the largest hex wrench in the tool set for this. Proceed as follows.

    1. Turn off the power switch to the motor.
    2. Unthread the needle.
    3. Remove the bobbin cover plate so you can see the bobbin case and hook.
    4. Set the stitch length/direction lever to the zero feed position. You can verify this by placing a piece of leather under the feet and hand wheeling a hole in the leather while adjusting the lever, until the needle goes into the same hole without moving the leather..
    5. There is a removable round cover plate on the lower right front of the machine. Unscrew and remove it. Keep the screws in a safe place.
    6. Slowly rotate the hand wheel toward you from the top down, anti-clockwise, while peering into the now open hole.
    7. You will see a clamp on a shaft that exposes a large hex bolt head as you rotate the wheel. That bolt clamps the shuttle driver shaft in place.
    8. Your goal here is to watch the hook as it approaches the rising needle's eye then move the hook into the correct position above the eye. This is done by loosening the big bolt and moving the shuttle by hand.
    9. When the needle has moved up between 1/8 to 3/16ths of an inch from bottom dead center, the hook should intersect the center line of the needle, about 1/8" above the top of the eye. You can move the hook by loosening that big hex head bolt inside the right front of the machine, which allows you to move the hook by hand pressure.
    10. That bolt will probably be very hard to turn initially. You can employ a vise grip on the hex wrench to add turning power to loosen it.
    11. Most likely, the bolt head won't line up with the opening in the body at the right point in rotation to time the hook. That would be too easy. So, I usually loosen the bolt, then apply the slightest pressure to tighten it just enough to hold its position until I move it by hand. You can do the same thing.
    12. Once you have re-positioned the hook to intersect the prescribed distance above the eye, as the needle ascends, tighten down the big bolt as tight as you can get it.
    13. Re-thread the needle and try sewing in forward and reverse. If the stitches are perfect and don't skip any more, tighten down the big bolt with the vise grip and replace the cover plate.

    Thanks, I'm about midway down the list and have located the hex wrench... thanks I'll print this out with and attach them to the illustrated manual pages. gonna give it a try.

  4. Posted · Report reply

    So do the diagrams and illustrations in the Juki manual correspond to what your Cobra 4 looks like? Going through the manual in sequence and comparing your Cobra 4's adjustments with what they should be should tell you what is off, how to adjust it, and where the set screws are. It's one of the best service manuals I've come across.

    Thanks Uwe yes I think it is pretty close I did manage to locate the hook driving shaft crank screw and so now I'm looking for the hex wrench size I also have to locate a regular wrench since I have a good bit of arthritis in my hands so it is hard to get much muscle behind the thing. getting there but I believe it will work, hope so.

  6. Posted · Report reply

    Thanks Guys, I've contacted a couple of people but apparently I'm not able to describe what the problem is. Thanks Uwe, at least I can know what the parts are called, isn't exactly what I thought I was trying to do but I'll try looking at it awhile see if I can understand how to adjust things. A good part of the problem with fixing without illustrations or a video is the lingo, I'm not fluent in machinery, so I don't know how to describe what I'm seeing. I tried to put a video together but it bounced all around so I'm not sure it would be much assistance in determining the problem. I'll keep trying.

    The Juki TSC-441 Service Manual describes how to adjust this class of machine (Needle-to-hook/shuttle distance adjustment is on page 4&5). Depending on how faithful the Cobra 4 clone really is to the original, it may be helpful.

  7. Posted · Report reply

    Would really appreciate some help in resolving a problem that I've been having with my Cobra 4 stitcher. I know I probably am not using the right words to describe a problem that I'm having but my bobbin hook doesn't line up with my needle as the needle starts to come back up and I'm having a problem with skipped stitches. My hook isn't lined up and I don't know how to move it into the right position. The bar holding the needle is in the right place when it is in full up position, but the hook on the bobbin assembly isn't and I can't move it either... so that is my question how do I line the bobbin hook up so that the timing of the bobbin is correct. I am just trying to get it into proper position to correct the stitching problem Thanks Debbie

  8. Posted · Report reply

    Thanks Bob, I spent the afternoon looking at things and orienting myself with all the pieces and I think I understand what you are saying. The belt I think is probably the most challenging aspect for me but I talked via email with Eric this afternoon so I think I'm getting the picture of how to do that. Just remains to be seen if it works afterwards. Think I'll give it a go tomorrow because I'm getting behind on work as well. Thanks Debbie

    It's real easy ,take the switch & wires off, then unfasten treadle rod off motor arm, on the motor there's 2 bolts side by side.Just loosen these 2 nuts 2turns,then on the other side take the nut all the way off the bolt.Push the bolt out of the table & now you can slide the motor off.and slide the new back on put the bolt back in tighten them,fasten switch & wires & adjust belt tension.

  10. Posted · Report reply

    I've had some of the same problems I haven't worked out everything yet, but I did manage to stop breaking needles and ruining leather. Part of my problem seemed to be the type of leather I was using. I do notice that it works very well on vegetable tanned leather and not as well on naked leathers. It does seem to have a problem with making the stitch look both the same on the top and bottom of the stitch although I've tried adjusting it and tweaking it all over. Part of the problem it seemed was that because I worked with other finishes the leather would be sucked down with the needle and as the project grew it seemed to pull needle around. My solution was to loosen the tension a lot! then gradually tighten (although I still haven't been able to match the top and bottom stitch). I added a box to extend table to lighten the pull of the weight of the leather and I also have used hand stitching in those areas where I seemed to have trouble or hand crank lifting the item to relieve the pull. It isn't a perfect solution and I still am having an industrial machine repairman come in and help me make adjustment, a fix a few things for me, if I get a moment of time to stop working on projects, until then I'm just making it work as best I can.

    I can say this however, the machine goes through a lot of leather, with no problem, and after I did all the above it seems to be starting work with the projects I've been doing. To date I've worked with Buffalo Leather, Mellow tan, and Hair on Calf on this machine. I came here looking for a bobbin winder suggestion so guess I'll get back to that.

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