Different leather becomes wrong tension?

[unionattic]

My  Pfaff 471 was operating ok with my leather once I used a heavier needle (#18).  This weekend I worked with a new hide of leather.  It's same thickness (~1.4mm) but is significantly stiffer, harder, shinier than the stuff I first used.  Both are veg tan leather.

What I discovered was that setting that worked well on the original leather worked terribly on the new leather.  The main complaint is the top thread lies on top of the leather, flat, and the bobbin thread comes up and loops over, very proud.   I also realized that needle size affects this -- the larger the needle,  the worse the top-thread-flat effect is.  

I''m using size #30 Serafil thread.

I suppose that I may have mis-threaded the machine.  Two things that bother me is whether Point #5 is correct,  as the thread never presses against that light wire spring very much.  Also the small tension wheel #7 doesn't always seem to stay tight into the discs.

So it's like there are multiple independent variables to adjust here. Potentially top thread tension and needle size.  Further confounding the problem is that this was just a test on a single ply of leather.  Ultimately I will sew several skived layers of this leather for a wallet,  so even thicker.  How should I approach tuning my machine?

I've posted an album with an example topstich of both leathers in three needle sizes.

 

 

 

 

Edited November 3, 2019 by Northmount
mentioned the threading. Added photos incase 3rd party hosted files are lost

[dikman]

At 5 you've got it coming off the check spring, through the guide and up to the arm - try going from the check spring directly up to the arm then back down through the guide.

[Constabulary]

not sure - looks like you have not pulled the thread over the nose in the tension unit

Different tension unit but same principle

 

Also download a manual and read it.

https://www.manualslib.com/manual/833625/Pfaff-471.html

 

 

Edited November 3, 2019 by Constabulary

[RockyAussie]

From what I can see you are getting too much top tension. This may be because I believe you have the thread at position 5 in the wrong place. Your thread return spring can not operate with the thread going through behind where you have it. It should go from the spring straight up to the thread lifting arm at 6. In your first position it dos not show your thread path back to the cone. I would have expected to see it raising up to stand behind to a thread loop and down to the cone. Serafil is a very slippery thread and tis possible that your bobbin may need to be tighten a 1/4 turn as well.

[Matt S]

In a word, yes. It's often the case that changing any quality of the leather or thread will affect how your machine sews. Variations in leather thickness and hardness are the largest variable factors, as they affect how the machine forms a stitch. One thing that often catches me out is glue -- how much, how dry and what type affect where the loop/knot ends up.

First thing to adjust, for me at least, is always the top tension. Solves about 90% of problems. Then the foot pressure, then needle size. Bobbin tension as a last resort. That assumes I've got my other ducks in a row and I know I'm working within that machine's capabilities.

[Wizcrafts]

Theoretically, you can balance the position of the knots in any material by a proper combination of thread size, needle size, bobbin tension and top tension. But, soft materials tend to give/pucker more that stronger materials. It's remotely possible that the otherwise great top/bottom tensions in soft leather won't match the outcome when sewing stiff leather. If you back off the bobbin tension a bit, then rest the top to let the knots drop, it should look better. Stop backing off before the bottom thread gets too loose underneath. If the bottom tension is still too strong, reverse the direction of the bobbin so it feeds inline with the slot in the bobbin case. Rely upon your anti-backlash spring to keep the bobbin from spinning on its own.

[Northmount]

7 hours ago, unionattic said:

I've posted an album with an example topstich of both leathers in three needle sizes.

Third party hosted files often disappear over time due to changes in the host's policies, files being moved or deleted, host goes out of business, etc.  When this happens, the thread becomes useless for future readers.  Please post your photos on Leatherworker.net to prevent this.  I downloaded your files and added them to your original post.

Tom

[Wizcrafts]

Regarding location #5 in the OP's machine photo, because the check spring was threaded incorrectly, it can't move up and down to manage the slackness of the thread feeding up to the take-up lever. There has to be some slack in the thread so it can go around the bobbin case without too much friction (and making a snapping sound). The spring's job is to keep the top thread taut until the needle pierces the material. Then it stops moving and gives the top thread enough slack to create a decent loop for the hook to pick off. Without a check spring there might not be a decent loop at all. Tight top thread makes it hard to balance the knots and puckers soft material upwards.

[unionattic]

First thing I've tried is to re-thread the machine according to the advice above.  

But the problem is that once the machine runs, the thread flips off the spring at #5,  and quickly the entire system loses all tension and the stitching is ruined.  

 

The spring at #5 has a hard stop that stops it from rotating counter-clockwise any further, so it doesn't put much tension on the thread. Also the shape the spring is rounded along the edge, and it basically flat across,  so it's easy for the thread to slide off to one side or another of the spring.  I will attach a close-up picture of the #5 assembly.

I have an ancient, hard to read manual for my (1950-era pfaff) and a modern manual for a modern version of 471.  Both seem to show that spring at #5 being substantially more loaded when threaded  than mine is.   May the spring is somehow adjust to be too forceful?  Or the thread is still somehow not following the proper path?  But indeed, neither manual diagram shows the thread passing through #A twice like I did in my original posted picture.

  

 

 

 

 

Edited November 6, 2019 by unionattic
typo

[unionattic]

I investigated the spring and disk around #5 to see what adjustments or freedoms were available.    I took off a locknut, removed the disk, and discovered that the pin which prevents the disk from rotating appears to be either a repair-job or a homemade addition.  Nothing else on this german? swiss? machine is so crude. It's a tiny roughly-sawn rod that is silver-soldered into the machine.    I don't see anyway to adjust the location or tension of the spring with this setup.

 

 

[unionattic]

Bumping hoping someone has a suggestion for this thread-path quandry.  

[Constabulary]

#5 (on your picture above) is not for putting tension on the thread it is for regulating the thread slack. Also seems your check spring stop is too low (I guess). Its should hold the thread tight / under tension until the needle touches the needle plate (approx) . You can adjust is by loosening the screw that holds the spring stop (curved piece of metal). The soldered pin looks odd but seems to be technically okay.

at your yellow #a the thread guide looks like a Singer 111 thread guide - I think. Anyway in this case I would only let the down going thread pass this guide. But should not be a too big issue. The Pfaff thread guide should look approx like this (see last 2 pictures)

Again - make sure you pulled the thread over the tongue in your thread regulator (your #5) see the video I have linked - THAT IS MOST IMPORTANT!

 

Edited November 8, 2019 by Constabulary

[unionattic]

Constabulary you sorted everything out for me, thanks. I didn't realize that I could pull the thread up and over the prong in the disk.  

Album of what I think is properly-threaded + detail of the spring tension plate.

(sadly youtube seems to be ignoring the "slow motion" of the iphone movie -- it's running at full speed)

 

 

 

Edited November 11, 2019 by unionattic
slow mo wasn't slow