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I've been reading a lot of posts learning as much information as possible about how these things work. I decided I'd share what I've learned about my Juki LH-515 over the past couple weeks of tinkering with it. Hopefully this will help anybody who's thinking about purchasing or has one of these and knows nothing about it like I did at the time. Sorry in advance this is a long read. I'm fairly new to sewing and have really never worked on a sewing machine prior to this, so please light me up if you see something I did wrong, bad info etc. Any help offered is greatly appreciated. The Juki LH-515 is a lockstitch, mid 80s machine. The stitch length is adjustable via pressing and holding a button on the machine base and rotating the balance wheel toward you and matching the numbers on the balance wheel to a red dot on the body. The needle spacing can be adjusted from a 5/32" to 1-1/2"; the standard width is 3/16" per the manual. You have to purchase new hardware to accomplish this. I purchased just the head and oil pan for $500 which seemed like a decent price to me. I've put a couple hundred more into the table, servo motor, and other various pieces. Make sure if you go this route it comes with the oil pan. Good luck finding an oil pan if it doesn't! Additionally, I have a Goldstar GBSM-550 servo motor, it's ok but it's no comparision with respect to slow speed and control as compared to the Sailrite MC-SCR motor setup. There's a $450 price difference between the two, so that's a future upgrade. My machine was unfortunately damaged in shipment; one of the spring tensioners was broken off, a thread guide was broken, and the thread take up lever guard was smashed. I replaced the needle bar, couple missing screws, and changed the needle spacing from 1/4" to 3/16". I also drilled and tapped two screw holes to which I attached a Sailrite swing away 3/4" binder attachment. Helpful Manuals LH-515 Instruction Manual: http://www.dsinternational.com/flipbook/juki/LH-512,_LH-515_INSTRUCTION_MANUAL_DSI1.00-AMG_040214/ LH-515 Parts Manual: http://www.dsinternational.com/flipbook/juki/LH-512,_LH515_PARTS_LIST_DSI1.00_AMG_021014/ LH-1152 Instruction Manual: http://www.dsinternational.com/flipbook/juki/LH-1152-4_INSTRUCTION_MANUAL_DSI1.00_AMG_040314/ LH-1152 Engineer Manual: http://dixiesewingmachine.tzo.com/MANUALS/JUKISERVICE/LH-1152-4%20Engineer%20Manual%20(%20No-VI-5-1).pdf The instruction manual for the 515 leaves a lot of questions unanswered, some info seems to have been lost in translation, and some is just plain wrong. The 1152 instruction manual and particularly the Engineer manual proved very helpful and reason I included it. The 515 and 1152 while similar in operation are different machines; I always defaulted to any measurements given in the 515 manual. Adjusting the bobbin case opener levers while discussed in the 515 manual is better explained in the 1152 engineer manual. These posts were also very helpful: Changed to a thicker thread and all hell broke lose: http://leatherworker.net/forum/index.php?showtopic=62884 Singer 211 Clone Hook Timing: http://leatherworker.net/forum/index.php?showtopic=59625&hl=%2Bsinger+%2B211+%2Bclone Consew 226 R1 Top Thread wrapping around the bobbin case: http://leatherworker.net/forum/index.php?showtopic=47044 Parts: http://www.cutsew.com/catalog/#/208 Pages 208-211. Have made several purchases from these fine folks, ask for Nick. There are plenty of good sites out there but I really like this catalog, keep it simple stupid approach. Tools: 1. Flat head screw driver with a long shank to break loose any stubborn set screws and to retighten. 2. Standard Allen wrench set. If you have a metric set keep it handy. 3. A stubby flat head screwdriver with a fine head to adjust the case open lever screws. 4. Fine straight slot screw driver to adjust bobbin tension. 5. Metric ruler 6. Metric feeler gauges 7. Tweezers Repairs & Tweaks: 1. Cleaned. The machine was literally cake in thread fuzz that was soaked with oil. It looked like Spanish moss hanging off of everything which turned out to be a blessing in disguise because it protected the metal from rust. I used Q-Tips to fish the gunk out as best I could. 2. 1st Thread Tensioner Replacement. The first one I ordered was a knockoff that could be used on other model machines. I had to drill out the top mounting hole and drill a lower mounting hole. Nothing about this worked from the start. I swapped the majority of the left over parts from the broken tensioner, filled on it, cussed at it, and managed to get it working. This was a waste of money and time, although I did learn a lot, order a genuine Juki part. I went back and read the manual and discovered much to my amazement I had the thread routed incorrectly coming off the tensioners, so I it may have worked had I oriented the thread properly. 2nd. Genuine Juki Tensioner, yep installed like it was supposed to and operates flawlessly. 3. Thread take up lever Guard. Was smashed in shipment, I bent and tweaked it back into shape, nothing exciting. 4. Needle Bar. My machine as mentioned earlier was setup with a 1/4" needle spacing, I wanted a 3/16" for the 3/4" binding tape I'm using. I purchased a "kit" that comes with the needle clamp, foot, feed dog, and throat plate off of Ebay. The needle clamp is a screw type as shown in the parts manual, the clamp that came with my machine was held in place with a set screw. I presume this was a modification done from whatever factory this machine came out of. So I ended having to replace the needle bar with one that had a threaded hole my new needle clamp could screw into. Before I removed the old needle bar I positioned it at bottom dead center and marked the bar where it met the bottom side of the machine as a reference point. I then transferred that measurement to the new bar and installed it without issue. Fortunately, the machine has a plastic plug on the top of the machine that will allow the bar to be removed. 5. Needle Clamp. I placed some blue Loctite on the threads of the new needle clamp and tightened the dickens out of it. If the clamp comes loose during operation bad things will happen. Once it's tightened install the needles and make sure they're squared to the face of the machine fit into the holes of the feed dog. To do this you have to loosen the needle bar and make the adjustments. (This only corrects your angle problem not the fore and aft positioning of the needles.) 6. Needle Positioning. Adjusting the positioning of the needles forward and aft in relation to the feed dog isn't discussed in the 515 manual; refer to the 1152 Engineer manual pages 6-7. (This adjusts the movement of the feed dog in relation to the needle, not the needle to the feed dog.) Take your time with this; it needs to be in the sweet spot throughout it's travel. You can make small tweaks by adjusting the two set screws that hold the feed dog in place. Also, if you remove your feed dog you need to re-check this. 7. Adjusting Hook Saddles. When you change the width of the needle spacing the hook saddles have to be adjusted to move the position of the hookst to the correct position with the scarf of the needles. Page 13 of the 515 manual explains this but fails to mention the hook drive gears also need to be lessened and moved. Pages 8&9 of the 1152 Engineer manual explains this and bobbin case opening adjustment. When I moved my left hook saddle, I found nearly 2 feet of the thread wound around the hook drive shaft, hidden between the saddle and hook shaft gear. The saddles may need a-little hammer persuasion to tap them into position, mine didn't slide effortlessly. 8. Feed Dog Height Adjustment. Page 14 of the 515 manual covers height adjustment and the information is wrong. The two set screws in Fig 25 secure the feed dog and will do nothing to adjust the height. Refer to the 1152 Engineer manual pages 12 & 13, I set the height per the 515 manual. Once the set screw is loosened I held the balance wheel and pushed the feed dog down to the correct height then tightened the set screw. There's also a small screw with a locking nut that'll offer you some fine adjustment. 9. Timing. I'm no expert so your mileage may vary. The timing my machine was strangely set out of whack for some reason, by a lot. Timing is covered on page 11 of the 515 manual, while the manual shows you how it should be set in Fig 18, it doesn't explain how it's done. Also you can easily throw the timing out if you move the saddles off the hook drive gears so move them carefully. a. Start by verifying the needle/timing belt relationship first, fortunately mine was correct. Refer to page 17 of the 515 manual, I used a small mirror positioned behind the gear to find the set screw and marked the accord tooth of the gear with a sharpie so I didn't have to slide the belt over to find it. b. Make sure the needles are in the proper position, bring them down to the lowest position, then raise the needle bar up 2mm, see page11. I adjusted the bobbin case timing marks by moving the saddles off the hook drive gears, then turn the bigger of the two gears shown on page 22 of the 515 manual. You'll need to move the gears past the desired setting because when you slide the saddles back on the hook shaft gear the saddle gear will rotate a few degrees as the teeth line up. I had to play around with this for awhile to get it just right. Make sure you hold the balance wheel steady you don't want it to rotate as you mate the gears. Don't worry about the hook relationship at this time, it will be adjusted later. Once you have the timing marks lined up, verify the hook is set to the proper distance with respect to the needle scarf as shown in Fig 21B, page 12 of the 515 manual then lock the saddle/s down. c. Hook timing is described on page 12, and refer to page 13, fig 22 for set screws to loosen to adjust the hook position. There're two set screws on this gear you need to loosen. When the needle is in the correct position, 2mm up from bottom dead center, you should see one screw you maybe able to access and if you rotate the balance wheel the other screw will come into view. Loosen the second screw first and turn the balance wheel and reposition the needle back into it's correct position mentioned earlier. The two set screws secure the hook shaft, loosening them allows the hook shaft to rotate. Loosen the first set screw and rotate the hook into the correct relationship with he needle, then tighten the first set screw down. Slowly rotate the balance wheel and tighten the second set screw. 10. Bobin Tension. Bobin tension adjustment is shown on page 8, Fig 13 of the 515 manual. I removed the bobbin cases and adjusted them like any other bobbin. This also allowed me to clean underneath the bobbin cases. I had a nice size chunk of thread fuzz stuck in the bobbin tension spring on one and a considerable amount of gunk underneath them both. The bobins can be adjusted without removing them. 11. Bobin Case Opening Timing. This setting was the hardest for me to wrap my mind around as I couldn't find any videos out there showing it. Even now I only feel like I'm 80% understanding it. The 515 manual describes it on page 11 but not very well, the 1152 Engineer manual pages 8 & 9 does a better job. This along with some great posts here have been a huge help. (Left Bobin) When the hook grabs the left thread, it wraps around the hook and will be on the operator's side of the tab underneath the throat plate. As the hook comes around pulling the thread, the case opening lever will be traveling towards the bobbin case, at approx. 180 degrees of rotation from picking up the needle thread the case open lever will tap the bobbin case and open up a small path that will allow the thread to travel over the top of the small tab in the throat plate. From there the upper needle thread picks up the bobbin thread as the hook finishes it's rotation and forms the stitch. Maybe if they called this something else it wouldn't be so confusing. Bobin tap adjustment? That's what your doing. You're adjusting the case opening lever, the lever that taps the bobbin case so it opens the gap at the throat plate for the thread to cross over at the correct time. The bobbin case basically floats in the hook assembly, and the Gib holds it in place. The only thing that prevents the bobbin case from spinning with the hook is that small tab that fits into and underneath the throat plate. The hole the tab fits into is slightly bigger. As the hook spins clockwise the tab is pulled towards the front of the machine(operator"s side) and held there via centrifugal force. The right bobbin is pulled the rear. The case opening lever taps the bobbin case and counteracts against the centrifugal force of the spinning hook and creates as small gap in the throat plate for the threat to pass over. If you look on page 8 of the 1152 Engineer manual it provides a good drawing and adjustment criteria. On the left bobin, find something you can push and hold the tab towards the rear of the machine ( I cut the end off a Q-Tip, anything metal is a bad idea), push the tab until it contacts the aft rib of the throat plate and hold it there. Turn the balance wheel towards you and observe the movement of the case opening lever (item 1, fig 20, page 11). As you turn the hand wheel the lever will start moving towards the bobin case(the arrow point) keep turning until it's moved towards the bobin case as far as it will go. (You may need to loosen the set screw that holds the lever, item 2 page 11 to allow it to fully travel.) You need to adjust the distance between the lever and case when the lever has reached the end of it's reward stroke. Now while holding the bobin tab towards the rear rib of the throat plate make sure you have a .2 -3mm (set mine to .2mm with a feeler gauge) gap between the lever and the bobin case. Once you have the setting zeroed in do the same to the other side. Once you have both sides done, make sure the timing of both sides match as closely as possible. The thread is traveling over the top of the hook assembly and bobin case, look at yours very close and make sure there aren't any burrs the thread can catch on. Here's a slow motion video of the machine running. https://www.youtube.com/watch?v=OL3QgyAI1bg How does it sew? Prior to installing the Genuine Juki thread tensioner and zeroing in the case opening timing, not good. I've experienced a lot of thread breakage on the left side that I attributed to timing an tension problems. Additionally, I've done an exhaustive search for S-Twisted thread as the manual recommends it for the left needle. no luck in finding any. I turned the left needle slightly to so that the outside hole of the needle is angled to the operator's side of the machine. The manual suggested orienting the needle in this manner if thread breakage was occurring. I'm sewing 1000D Cordura Nylon, using V69 bonded nylon thread with 135x17 needle, think that size #18. Would I go this route if I had it to do over? Probably not, I really wanted to be working on my projects by now. Any machine can break, we're either going to fix it ourselves or pay someone to fix it. The tradeoff is l learned a lot while my projects waited. I think in the long run I'll come out on top. As much of a pain this thing has been, I have to admit I've had a lot of fun working it and learned in detail how these things operate. Hope this helps somebody out there. Best of luck on your projects and machines. Have a good one Got the links working.