Juki 441 clone was missing stitches

[esantoro]

I was doing a bit of experimenting today with a 23 needle and 138 thread. My Juki 441 clone was missing too many stitches for me not to be concerned. I could clearly see that the little hoop made with the top thread doesn't flare out enough for the shuttle hook to catch it. Everything is fine with 207 and 277 thread.

I'm thinking that there may be a few possible reasons for the skipping.

1. My 138 thread has dried out a bit (don't use it much), so I ought to run it through the lube pot with some Lexol in it. I could also try a different brand of 138 thread. The thread also frayed and broke a few times even with the top tension backed off.

2. The 794 needle I'm using has the "S" designation (narrow cross point) while the larger needles I use are all diamond points, which means the head is a bit wider and possible aids in looping the top thread to be caught by the hook.

3. I have a Chinese Juki 441 clone. Maybe I should buy a Japanese made shuttle hook.

Thanks for any suggestions you can offer.

Ed

[Luke Hatley]

just curious, what will happen if you put a size 18 needle in the machine

and use the 138 thread ?

[esantoro]

just curious, what will happen if you put a size 18 needle in the machine

and use the 138 thread ?

The smallest needle I can get for this machine is 23 (794 system).

[Art]

Hi Ed,

Luke is right, the first thing to try is a smaller needle, an 18 (110) or 19 (120) might be ok for Coats poly, but for Lynhanl or other nylon, you might need a 21 (140). Size 23 (160) is way big for that thread (138) and the hole the needle makes is probably not holding the thread tight enough. The absolute FIRST thing to do when having a problem is to put a new needle of the correct size in the machine. Also, get a lube pot. Then we need to know:

What machine, Make and Model

What thread, Make and number or name, size top, size in bobbin

What needle, Make and number or size

What material you are sewing.

Chinese hooks and shuttles aren't bad and it will take some grand amount of sewing to wear them out (assuming a little basic oiling), replacing major parts is the last thing you want to do. Chinese parts are not a bad thing necessarily, Japanese and American parts are important if you are going to run a machine hard (still got to oil it though).

Thread (modern) will last years if kept away form the sun in a stable environment (and I don't mean out in the barn), lubing it always helps. Bobbin thread can get old much quicker as it is wound on a tighter circumference and can take a little set especially toward the end of the bobbin. Ten year old thread kept in a box in reasonable temp and humidity is perfectly useable although it won't have the advantages of advances it the industry that the new thread will have.

The 794s is available in Schmetz, Organ, and Groz Beckert from 100s to 250s (16 to 27 Singer) at least, maybe smaller. Not many places carry the 100s in the 794s but 120s are very available. Size 100 in a 794 machine is really going to get abused as are 120s, kind of like putting an allison motor in a mini-cooper. You will break smaller needles and you MUST find all of the needle; if you can't you will have to check the shuttle race to make sure it's not in there as it can gaul up the race pretty bad. I like Schmetz brand for availability and hardness, I feel the Organs are a little soft for what I do. Needless to say I break more Schmetz and bend more Organs. You can get Schmetz from Artisan and Organ from Ferdco. I don't know who is handling Groz Beckert, but they are good also.

Art

The smallest needle I can get for this machine is 23 (794 system).

Edited August 23, 2007 by Art

[Bob T]

The very first thing is take out the needle you have and put in a new one making absolutely sure it seats properly in the needle bar and is oriented properly to the hook. You may not of installed the current needle properly. We've all made this mistake causing the same results you're getting.

Beyond this, my opinion differs from those above. If you use too small of needle, the hole in what you are sewing is too small then the thread hangs up in the material putting tension in the thread as the needle makes it's downward stroke. When the needle reaches it's lowest point and starts to rise, the loop starts to form but the tension in the thread from the material doesn't allow the loop to reach the right size, the hook misses the loop, causing a skipped stitch. This can also happen when you have too much top tension.

I sew a lot of 138 thread with size 23 needle and it seems to work well. The second possible cause, is the needle height is either too high or too low. When the hook tip passes by the scarf of the needle check to see its position. From it's lowest point, the needle should rise about 1/8" before the hook tip passes by the center of the scarf. Typically, a jammed stitch will force the needle bar up in its holder and the hook tip will then pass right at the eye of the needle, missing the loop and thus the stitch.

The next possible cause is the hook tip is too far from the scarf when it passes the scarf. The box your hook came in should contain some shims to shim out the hook. You want the hook tip to be nearly flush with the back of the needle at the needle shaft, not the scarf. Good Luck.

Edited August 23, 2007 by Bob T

[Art]

Hi Ed,

I like Bob's explanation also. I sew all day (when I can get into the shop) with Rice 138 nylon and a 21 needle or Coats 138 poly and a 19 needle. I never (oh boy I hope I don't live to regret this) skip stitches, however my 618 is setup for a 21 needle, and a 19 doesn't seem to cause any alignment problems (hook/needle). Your 441 may have been setup for a 26 needle and a 23 might be a nats hair too far, especially if it was a loose 26 setup. I have mine (4000P) setup pretty tight for a 26 and I can use a 25 or a 24 ok (seldom do) but I haven't tried a 23, I just run a 230 (26) needle for 207 to 346 and it works fine. Even 415 works with the 230 and is real tight and very consistant. However, all this only works if the needle is in correctly and threaded properly.

Everyone who hasn't done so should take their machine when running and stitching well and take the thread out (top and bobbin), take the needle plates and feet off, and look at the alignment of the shuttle/hook as you slowly pull the machine through, this only takes a couple of minutes to do, the relationship of hook to needle is important and you should be able to eyeball this and see that it is correct. Put a bigger needle in and see if it is still correct, put a lot smaller needle in and see how this relationship changes. The bigger needle may strike the hook or skim it and I have seen machines that run well this way (skimming), but smaller, two or three sizes smaller, can leave a lot of room in there. Some machines tolerate this better than others. But there is a big difference between a 19 and a 21 and a 23 and a 26.

So set your machine up for the needle range you use most or do like I did, get two machines (or 3 or 4 or 5 or 6). There is not a setup that will cover #16 to #27 needles for 69 to 415 thread, there is always going to be a range that works acceptably and only one that will be dead on. Ok, so they say their machine will sew however thick sole bends to a dollar bill with no adjustments (other than some minor tension adjustments), and they can prove it at the shows, just don't try and change the thread or needle so it looks nice or it might start skipping stitches......or worse!

Now some really good news:

Artisan Dave has joined leatherworker.net and works with Jerry and Steve at Artisan. Since he has been in the sewing machine business for 35 years prior to joining Artisan this past January and knows about Consew, Mitsubishi and a bunch of others probably better than most, he will be an asset here. I'll let Dave blow his own horn when he is ready, but if you have some questions about Artisan equipment, give Artisan Dave a shout direct through leatherworker.net or at Artisan if it is not something easy someone here will know right off the bat.

Art

Hi Ed,

[Bob T]

I want to add a small comment about the Chinese clones. I have a Chinese Adler 366 clone and generally, the castings, shafts, gears, etc. are pretty good, but the set screws, bolts, allen screws, etc. etc. are awful. The problem this presents is it is hard to tighten them up where they hold like they are supposed to. Consequently, it is pretty easy to knock the machine out of time. My solution is to completely replace every screw, bolt, allen screw, etc. with American made products. Since doing it, I have not knocked my machine out of time even once. Fortunately, they use standard off the shelf sizes so I can get replacements closeby at Ace Hardware.

Edited August 23, 2007 by Bob T

[Art]

Hi Bob,

I've never stripped a thread in one, the head always rounds off before I get that far. They must not heat treat them at all. American tools (hex keys, screwdrivers, sockets, or box wrenches) bugger-up those Chinese screws all the time, but then American screws (and German) will mess-up Chinese tools. Even Chinese tools mess-up Chinese screws, and if you ever see a phillips or cross point screw in anything from China, replace it because you have one chance to put it in and one to (maybe) take it out.

Also, if anyone wants to work on their machine, get a good set of American Metric hex keys, the metric are the only ones that fit metric screws, some of the inch sizes seem to fit but really don't.

Now for a real vocabulary exercise, try and remove a Chinese screw with threadlocker on it (well it wouldn't stay tight would it, so someone used Loctite on it).

Art

I want to add a small comment about the Chinese clones. I have a Chinese Adler 366 clone and generally, the castings, shafts, gears, etc. are pretty good, but the set screws, bolts, allen screws, etc. etc. are awful. The problem this presents is it is hard to tighten them up where they hold like they are supposed to. Consequently, it is pretty easy to knock the machine out of time. My solution is to completely replace every screw, bolt, allen screw, etc. with American made products. Since doing it, I have not knocked my machine out of time even once. Fortunately, they use standard off the shelf sizes so I can get replacements closeby at Ace Hardware.

[esantoro]

Thanks for all the fabulous schooling on this topic.

I'll call around tomorrow for smaller needles, though I've never had any luck finding 794 system needles smaller than #23.

I've been using a #24 for Coats 207 and a #25 for 277 (though don't use this much) I never thought to use a #26.

I'll try the lube pot tonight, as well as newer Coats 138.

I like the idea of replacing chinese screws with American counterparts. I'll think about this as I begin experimenting with needle bar adjustments.

Ed

P.S. I put a #24 needle in the machine. The hook slightly skims the needle on the downstroke. The upstroke has a tad less of a skim. Skimming is a smidgen more with the #25. With the #23 there is a very very slight skim on the downstroke and an indecipherable amount of skim (maybe none) on the upstroke.

Ferdco's website seems to suggest a #22 for 138 thread, but for the Pro 2000, to which my Chinese clone is similar, it doesn't recommend a top thread lighter than 207 (a #24 needle, which I use, for top and bottom 207). Should my Juki 441 clone even be used for top-thread lighter than 207. Ferdco's website seems to suggest no. I'll give them a call tomorrow.

Edited August 24, 2007 by esantoro

[esantoro]

The very first thing is take out the needle you have and put in a new one making absolutely sure it seats properly in the needle bar and is oriented properly to the hook. You may not of installed the current needle properly. We've all made this mistake causing the same results you're getting.

Beyond this, my opinion differs from those above. If you use too small of needle, the hole in what you are sewing is too small then the thread hangs up in the material putting tension in the thread as the needle makes it's downward stroke. When the needle reaches it's lowest point and starts to rise, the loop starts to form but the tension in the thread from the material doesn't allow the loop to reach the right size, the hook misses the loop, causing a skipped stitch. This can also happen when you have too much top tension.

I sew a lot of 138 thread with size 23 needle and it seems to work well. The second possible cause, is the needle height is either too high or too low. When the hook tip passes by the scarf of the needle check to see its position. From it's lowest point, the needle should rise about 1/8" before the hook tip passes by the center of the scarf. Typically, a jammed stitch will force the needle bar up in its holder and the hook tip will then pass right at the eye of the needle, missing the loop and thus the stitch.

The next possible cause is the hook tip is too far from the scarf when it passes the scarf. The box your hook came in should contain some shims to shim out the hook. You want the hook tip to be nearly flush with the back of the needle at the needle shaft, not the scarf. Good Luck.

Bob,

I read your post a second time closely. I was thinking the same thing about there being too much tension on the thread once it pierces the leather, not allowing a full loop to form. Though I am using a #23 needle is an "s" designation, narrow crosspoint. I think a diamond point will allow a slightly larger hole, thus allowing a more fully formed loop. I'll try the 138 with a #24 needle.

The following intrigues me: "The second possible cause, is the needle height is either too high or too low. When the hook tip passes by the scarf of the needle check to see its position. From it's lowest point, the needle should rise about 1/8" before the hook tip passes by the center of the scarf. Typically, a jammed stitch will force the needle bar up in its holder and the hook tip will then pass right at the eye of the needle, missing the loop and thus the stitch. "

I checked this. The needle rises about 1/8" and the tip of the hook is just about to pass into the plane of the needle, a hair's breadth.

Thanks for your post.

Ed