How to fix my CB 4500 needle issue?

[Pib]

Hello 

I need your help to fix my issue on my CB 4500

The needle touch this part (behind red arrow) and cut my treat.

I have followed the awesome Uwe video and check the hook timing.  It seems to be ok, but no way to know how the adjust this small part

Any idea?

Thank for this

David from France

[Northmount]

@Pib moved to leather sewing machines.  You'll get  more response here.

Tom

[Pib]

OK thank for this

[Mark842]

What size needle and thread are you using on top. Looks very large

[JLSleather]

That needle does look low.  That was built for clearance.  Make sure you are using a 794 needle and that it is fully inserted and it isn't bent.  If the needle is correct and straight, make sure teh shuttle assembly doesn't have anything behind it and it's tightened into position.  If those are correct, is the needle bar bent or misaligned? Is the lower feed deflecting the needle into the shuttle?

Your red arrow is in a bad spot to see right there, and we don't know if this is showing the down stroke or up.

 

Edited September 3, 2018 by JLSleather

[brmax]

Yes it does show on the needle that its trashed from hitting something and so will always cut/tear the thread as it passes up or down through the material. 

I should ask if this is a different size or bigger needle than previous in your setup. Just curious in that question, if the hook clearance now could be a bit close. 

In any case a needle change has to be made even if the clearence is ok. Sometimes we bump or just move the material and force the needle to bend and hit something in its path with this same  needle tip result. 

There are some adjustments in the needle position, though a bit more discussion could help in determination. 

Good day

Floyd

 

[alpha2]

What does your clearance look like where it goes through the needle guide?

 

[Uwe]

Here's a picture with just the needle and the shuttle driver. The green area on the shuttle driver is the needle guard which prevents the needle from coming too close to the tip of the hook. That green needle guard area on the shuttle driver is the ONLY part that is allowed to touch the needle, very lightly.

Edited September 3, 2018 by Uwe

[Uwe]

Your shuttle driver face looks quite worn in the needle guard area and the angled slope above it. Perhaps the needle comes down on the slope every single time and is deflected a large amount while it drags along the face of the shuttle driver. That constant friction metal on metal over a long time (and many premature needle deaths) may have worn your shuttle driver from a smooth face with rounded edges to a sharp knife-like edge that cuts thread.

It's possible that your machine was somehow set up with a shuttle race back that is too thick, which made the hook touch the needle. Then, instead of installing the correct shuttle race back, somebody adjusted the shuttle driver position to push the needle away from the hook tip. But that's just a theory based on a single photo.

To properly fix the problem, you may need to install the correct shuttle race back and also replace the worn shuttle driver itself. Installing the shuttle race back is relatively easy, replacing the shuttle driver may not be easy (I've not yet done it myself.) The parts may be hard to find and not exactly cheap. Plus, you don't even know yet exactly which of the seven shuttle race backs you need. At the factory they just have all of them available to choose from.

Before you start ordering parts, make sure that what I described really is the problem. I'm just guessing based on a single picture and I've been wrong many times before.  

Here's the parts diagram again that shows the shuttle race back (the red open ring) that comes in seven different thicknesses. Juki uses it to set the hook position relative to the needle on the Juki TSC-441 design. Normally that's done at the factory and never needs to be changed.

Here's another photo of my shuttle driver and needle from a slightly different angle:

Edited September 3, 2018 by Uwe

[JLSleather]

Well, that's sorta what I was talking about.  Maybe start with taking it out and making sure there's nothing behind it "shimming" it out and into the path.

[brmax]

Is there anymore results here on the needle position. Paticularly in and through the hole and feed dog, as you know it should be centered. Im curious of the above when the needle is not in a bind below. 

Those tips on checking the shuttle and shim area for debris is a great check, keep us posted. Its your lucky day with all these tips being posted, and before any above references to look at.

 

Good day

Floyd

 

ps:   Item of reference pg. 3 items 30 & 31

  http://leatherworker.net/forum/applications/core/interface/file/attachment.php?id=103092

Edited September 4, 2018 by brmax

[koreric75]

22 hours ago, Pib said:

Hello 

I need your help to fix my issue on my CB 4500

The needle touch this part (behind red arrow) and cut my treat.

I have followed the awesome Uwe video and check the hook timing.  It seems to be ok, but no way to know how the adjust this small part

Any idea?

Thank for this

David from France

Have you checked these two screws (extra red arrows)  there should be springs behind them and not torqued down tight...the cb3200 likes them just backed out enough to see the first coil of the spring between the plate and screw head.  also it's hard to tell from your pic if the hook is in the correct position, but if that is needle bottom dead center the thread cast off area? i think looks advanced, attached a link to another vid, if you notice the screw heads are backed out and you can just see the first coil of the spring behind...

 

[JLSleather]

2 hours ago, koreric75 said:

i think looks advanced, attached a link to another vid,

See, that's what I was thinking, but he said he "did" the timing. In this video, the position of the bobbin / shuttle is clearly not the same as the OP's pic. Compare position of the shuttle ...