CB4500 reverse stitch bottom loops

[RockyAussie]

This is just a thought that comes to mind as I have known of some sewing machine mechanics to tighten the shuttle race screws fully in tight.The 2 I am referring to are the ones with springs behind them.I believe if they are tight they can impede the thread from going around without being caught up.This following link I think should be checked around the 9 minute in mark to perhaps better understand.
https://www.youtube.com/watch?v=TvHgMDlfQo0

I initially received mine with them fully tightened and had some problems.I have not noticed any problems since I have loosened them and timed the machine following the Juki 441 engineers manual instructions with regards to height measurements. Thanks for the Video share Uwe and Wiz for your as usual superb break down of useful tips.

 

[Zandeosaddles]

On 05/26/2017 at 5:19 PM, Zandeosaddles said:

Good day all. I am having a problem with my machine. It stitches fine forward, but in reverse it makes loops underneath. I have run through all the instructional videos on you tube. All the basic checks are done. When in reverse, the machine sounds as if the tension of the upper thread is too tight as opposed to sewing forward, yet it is the top thread that loops underneath in reverse. I would greatly appreciate it if someone would take up the challenge of running through all the settings with me esp the uncommon ones. My machine was never properly setup by the agents in south africa. I got a technician out to set it up. I recently re did the timing, feet balance threading, oiling race screw tension from videos, just to be sure. The thread is wound correctly on bobbin.  my email address is zandeo@gmail.com. thanks very much.

 

[Zandeosaddles]

Hi Rocky Aussie. Thanks forthe advice, I have the screws on the race one full turm loose. The check spring theory makes sense butI would like to ask if a poorly functioning check spring should affect forward stitch as well?

GiGi, my machine is 3 years old and is not nearly worn. Could there maybe be a manufacturing glitch on one of the parts?

[RockyAussie]

Just a couple of things I've noticed by going back over Uwe's video. My hook goes back at least another 3 to 4mm than does Uwe's. It appears that the thread in Uwe's snags in the race and logically that could impede the bobbin/hook from falling back away when it should. I would guess as Constabulary suggested that the shuttle race packer needs to be a bit thicker in that case. I believe a coke can thickness could work if that helps.Equally if the race is not freely moving without thread in it the packer may be damaged or too tight for that size thread. Best of luck Brian

[Wizcrafts]

10 hours ago, Zandeosaddles said:

Could there maybe be a manufacturing glitch on one of the parts?

You betcha it can! I thought I would upgrade my CB4500 to a Juki hook, which cost about $250. It sewed perfectly in forward and virtually not at all in reverse! The top thread got pinched between the shuttle and the race every time I tried sewing in reverse. I backed out the screws to no avail. I retimed it to no avail. I finally cut my losses and went back to the OEM Cowboy hook. The lesson? Juki 441 hooks belong in Juki built machines.

Seriously though, your hook may have a manufacturing defect. Take the machine to a qualified Cowboy dealer, or ship the hook to one for inspection and possible replacement.

[Uwe]

There may not be a "qualified" Cowboy dealer in all of South Africa, since the original dealer/agent didn't really set things up correctly to begin with, according to the original post. Sometimes taking the machine in for service is just not an option. Well over 99% of all people do not live within driving distance of a qualified Cowboy dealer.

I'd say certain hook + race combinations just don't work well together. Mixing and matching parts between OEM (Juki) and aftermarket copies (Cowboy and others) does not always yield desired result. If an aftermarket copy is a truly faithful copy of the original, then the OEM parts should work. Some manufacturers make subtle design or manufacturing changes (on purpose or accidentally) that go unnoticed but result in poor parts interchangeability.

I have a feeling the issue of thread getting pulled into the race during reverse has, among other things, to do with very subtle differences in the curves and slopes of the shuttle hook tip itself, and also the shape of the right edge of the race and backing ring. Thread material, and how sticky/slippery it is may als affect this issue. If the thread does not want to slide back on the hook during reverse, it is more likely to get dragged into the race. A slight burr on the hook will have the same effect. Aggressive polishing of the hook tip may make things permanently worse. The opposing movement of hook and needle during forward stitches hides many imperfections and timing flaws. Sewing in reverse where both needle and hook move in the same direction, but at different speeds, is much less forgiving. 

I'm working through the hook timing instructions in the Juki TSC-441 engineering manual (Juki 441 Engineers Manual.pdf). It's not exactly intuitive and some steps don't compute in my head quite yet. Missing reference marks on the machine don't help, either. 

In the meantime, I made a video showing how my machine's race and shuttle hook fit together and how things come apart. Perhaps it will help others notice some differences, or confirm that theirs is the same as mine in the video.

 

[RockyAussie]

Excellent video as always Ewe. I found a video that I initially used to time mine and still had problems with missed stitches in reverse etc and when I followed the Juki guide as best I could it then went perfect. There was a large difference in the 2 different procedures as to where the hook ended up in relation to the needle height. The 25.9 height from the bottom of needle bar clamp and the throat plate seems a bit difficult (ha ha) but I rested a short ruler on the throat plate and got as close as I could see and now no problems. I believe that your hook is not going back as far as mine is Uwe and that may make the hook not fall back with gravity to open as easily at slow speed as is desirable. Logically a machine moving at some speed will make the hook throw back away more definitely as it reaches the end of its travel in either direction and is probably one of the reasons that miss stitches happen more when you are going slow. You'd think they would be able to work out some sort of alternating repulsing magnet to better force the opening on the hook. I should perhaps mention that I do not have any problems getting the reverse stitch lining up into the previous holes as it seems many do and I have not got any washers and so on to do this. Don't know why and if it develops I will have to find out I guess. Brian

[Zandeosaddles]

Thanks again to all for the very helpful replies. I am finding the engineers manual very helpful and Im re setting the machine according to manual. When I set the timing according to book. The needle height is not right. This makes me think the position of the needle bar relative to the drive shaft is off. The reference in the manual doesnt result in the hook to needle height relationship. Will also like to find the reference marks on the shaft of upper feed. Thanks Uwe for your inputs so far.

[Zandeosaddles]

Brian. Thanks for your input. It seems the distance between the needle bar and throat plate must be 29.5mm once needle has travelled up 5mm? I think we are getting close my shuttle friver touches the needle ever so slightly .

[Uwe]

2 hours ago, Zandeosaddles said:

It seems the distance between the needle bar and throat plate must be 29.5mm once needle has travelled up 5mm?

It may seem that way, but the manual states fairly clearly that the 25.9mm distance is the "Reference value of the lowest position of the needle bar stroke."

The shuttle driver is supposed to touch the needle slightly - that's what prevents the needle from getting deflected towards the hook (and getting hit by the hook.) The shuttle driver also acts the needle guard.

The Juki TSC-441 Engineer's manual can be confusing, especially if you read it on the computer one page at a time. The manual makes (slightly) more sense when viewed as two-page spreads, or printed as a booklet like this:

Now you have the target settings on the left, and directly opposite to the right you have instructions on how to change that particular setting.

Alas, the adjustment instructions for step 2. on the right side (middle of page 3) still confound me. But I'm determined to figure this out over the weekend. 

[RockyAussie]

5 hours ago, Zandeosaddles said:

Brian. Thanks for your input. It seems the distance between the needle bar and throat plate must be 29.5mm once needle has travelled up 5mm? I think we are getting close my shuttle friver touches the needle ever so slightly .

NO. That is wrong as Uwe has pointed out. The (25.9mm) is when the needle is at the absolute bottom. After that when the needle is raised up 5mm the hook tip should be lining up with the middle of the needle then. 2 different steps here . If the needle is in the bar fully and the needle bar is in its correct position the top of the needle eye to the hook tip should be 2.5mm apart as well. Hope that makes it easier. Regards Brian

[Zandeosaddles]

Thanks Brian. I get it now. As Uwe said, those manuals are rather vague. Uwe, my race does not offer the play or give which you show in your video with screws tight or loose. I will post my progress ad I go. Here in SA, technical service is poor at best. Thanks again.

[Zandeosaddles]

Ok. I found that the eccenteic cam at the back of the machine was not set properly ans the top feed cam next to it was not properly tightened. Now I have set it according to rhe juki engineers manual. Now I find needle bar height and hook timing is out. So I will set latter accordingly ans hope for the best. Please share whatever thoughts you have. I follow needle bar height point

[RockyAussie]

If possible please post some pictures of the parts you refer to and mention what adjustments you do .If you get all of it right it may help others and if you get it wrong we may see and pick up why. Regards Brian

[Zandeosaddles]

Thanks Brian. I will do. How do I shrink the size of the pictures.

[Zandeosaddles]

the settings I changed according to the manual caused the shuttle to not come into timing with needle at all regardless of what I do. so I am a bit lost. I need to have a sequence of what to set first in order to get the whole machine to ideal settings. The eccenrric cam at the back of the machine seems to affect the degree to which the shuttle and needle strokes and cycles function. Any advice is helpful. I am willing to execute technical instructions step by step. My machine is now totally dysfunctional. Eish!

[garypl]

Download Irfanview - a free, simple to use photo editing program.  Open your pictures in Irfanview, then select Resize in edit menu.   640 x 480 or 1280 x 960 pixels will work.

[CowboyBob]

47 minutes ago, Zandeosaddles said:

the settings I changed according to the manual caused the shuttle to not come into timing with needle at all regardless of what I do. so I am a bit lost. I need to have a sequence of what to set first in order to get the whole machine to ideal settings. The eccenrric cam at the back of the machine seems to affect the degree to which the shuttle and needle strokes and cycles function. Any advice is helpful. I am willing to execute technical instructions step by step. My machine is now totally dysfunctional. Eish!

I hope you can understand this,i'll try to explain this the best I can.The cam on the top shaft for the shuttle timing needs to be adjusted so that when you turn the machine & the needle bar is all the way down the shuttle is all the way back & coming forward just as the needle bar is coming up.Now when you do this you need to run the needle bar all the way down & watch it come up & then turn it backwards so that when the needle bar is all the way down & you turn the handwheel 2" either way it stars to come forward a the same position when the bar is all the way down.It helps to put the stitch length on 0.

[Zandeosaddles]

Thanks dor the photo advice Garypl

Cowboybob. Thanks. I do understand what must happen but im a bit in the dark as to the way to do it considering the settings given by the engineers manual did not result in the needle bar to shuttle relationship beimg right. Should I just experiment until I get it?

[Zandeosaddles]

Here are the parts in question. I dont know where to set the eccentric cam in relation to the mark on the shaft. Also the position of the large collar on the left. Is there not a guide for this eg when the cam is all the way pointing to the back?

[RockyAussie]

Here is another manual that I think someone said was easier to understand and it may help to cross reference with the other perhaps.It is a pdf file 

  .inst-441.pdf

[Zandeosaddles]

I will definitely check it in the morning. Crunch time now. Thanks for sharing.

[CowboyBob]

Ok,so the only cam to adjust for the hook is the one on the left that takes a 6mm.IF it isn't correct you turn it one way & will notice it'll get closer or further away from the way it's supposed to be.

 

 

 

[mikesc]

IF it isn't correct you turn it one way & will notice it'll get closer or further away from the way it's supposed to be.

Heh..I'm after thinkin that you'd maybe be having some Irish in yer ancestry there Bob so you might..:)

[Zandeosaddles]

On 2017-6-1 at 1:26 AM, RockyAussie said:

Excellent video as always Ewe. I found a video that I initially used to time mine and still had problems with missed stitches in reverse etc and when I followed the Juki guide as best I could it then went perfect. There was a large difference in the 2 different procedures as to where the hook ended up in relation to the needle height. The 25.9 height from the bottom of needle bar clamp and the throat plate seems a bit difficult (ha ha) but I rested a short ruler on the throat plate and got as close as I could see and now no problems. I believe that your hook is not going back as far as mine is Uwe and that may make the hook not fall back with gravity to open as easily at slow speed as is desirable. Logically a machine moving at some speed will make the hook throw back away more definitely as it reaches the end of its travel in either direction and is probably one of the reasons that miss stitches happen more when you are going slow. You'd think they would be able to work out some sort of alternating repulsing magnet to better force the opening on the hook. I should perhaps mention that I do not have any problems getting the reverse stitch lining up into the previous holes as it seems many do and I have not got any washers and so on to do this. Don't know why and if it develops I will have to find out I guess. Brian

Brian the guide seems to cover some areas better than the others. I want to ask. Should I loosen the lower timing adjustment screw as well when setting the eccentric cam. also Is it the eccentric cam which determines the relationship between needle bar height and hook position?