Consew 206RB balance and tension in reverse issue

[MAlan]

Good morning.  I'm stuck and am hopeful someone can help me get unstuck.  Yes - I have done a lot of searching and found plenty of results but no resolution.

First a bit of background.  I am a leather worker.  Mostly wallets, journal covers, EDC misc. - smaller personal basically.  Everything I have done has been hand stitched...  up to now.  Wanting to expand my product line to include leather, canvas (waxed) and a creative mix between the two I procured a used 206RB about a month ago.  With the exception of cleaning, oiling and replacing the clutch motor with a servo and some new presser feet (w/ guides) I haven't done anything with it except learn.  Everything I have learned has been with the help of forums like this, youtube and trial-error.  I have the manual as well but we all know it's limitations.

So why am I stuck?  I have been able to achieve what I think is a balanced stitch between top and bottom threads but ONLY in the forward direction - reverse looks horrible, on the bobbin side - especially when laid upon the forward direction stitches.  I have included several pictures to help illustrate my issue.  My observation (it's an observation only - I'm not experienced enough to even have an opinion yet) is as follows.

• Stitch line A) Forward direction only, top and bottom stitch seem as if the tension is balanced between top and bottom threads as observed on the front and back side of the photo.
• Stitch line Reverse direction only, top and bottom stitch are not balanced.  Bottom thread reflects a tension issue with the bobbin thread observed on back side of the photo.  Top stitch still seems visually balanced - but we know it isn't. 
• Stitch line C) Forward with direction with a reverse lock stitch at the start and end. Top and bottom stitch seem balanced in the forward only direction.  The ugly nature of the lock stitch demonstrates well the result of the forward/reverse tension tension balance issue.
•      

As an aside I have learned that needle positions vital when going in to reverse (I'd appreciate  any clarity on this or a "guide" - I've adjusted based upon observation and not upon formal guidance - my adjustment my not be accurate either) but that isn't whats causing this - it just add to the ugliness at times.  

Any help would be appreciated - I have made so many attempts at balancing between top and bottom - have changed threads and needles and continue to produce similar results to varying extremes.

• The leather used is 3.5oz combination tanned latigo.
• Thread is Nylon - Size 138 - Bonded - Nominal 
• Needle is Groz-Beckert 135x16, DPX16D, Nm 130/21 D/TRI (pictured)
• Threading as pictured (Consew manual)

I have attached several pictures that hopefully help.  If not, let me know what is needed to help out.

Many thanks!

Marc

 

[Uwe]

Your needle size seems much too small for size 138 thread. This may cause problems because the hole the needle creates is simply too small to consistently pull the knot tight in the center of the material, especially in hard leather. To make room for a lock stitch knot, the hole theoretically needs to be about three times the diameter of the thread. Soft vinyl is much more forgiving. Needle to thread size combinations depend on various factors, but your needle is much too small according to the chart below. Stepping up the needle size may alleviate some of your apparent irregular tension problems.

A whole bunch of things have to come together just so to make forward and reverse stitches line up perfectly and knots pulled tight evenly. Change one thing and all bets are off. 

 

Edited December 27, 2017 by Uwe

[trash treasure]

Uwe is 100% right -

We use a #21 needle with 138 thread, for sewing webbing - But that's relatively soft, and the knot buries fine - For leather, you want something larger yet .                    

Edited December 27, 2017 by trash treasure
fix spacing

[MAlan]

Thanks @Uwe and @trash treasure  I will make an adjustment today and report back.  I forget where I found the chart that i used to size needle/thread partnership but apparently it may have not been appropriate for leather.  The largest needle I have is a 140/22 P/NW.  I do have some #92 thread that I will partner that up with - we'll see shortly.  Thanks for the time and courtesy of a reply.  I really appreciate it.

[Wizcrafts]

3 hours ago, MAlan said:

Thanks @Uwe and @trash treasure  I will make an adjustment today and report back.  I forget where I found the chart that i used to size needle/thread partnership but apparently it may have not been appropriate for leather.  The largest needle I have is a 140/22 P/NW.  I do have some #92 thread that I will partner that up with - we'll see shortly.  Thanks for the time and courtesy of a reply.  I really appreciate it.

I use either a #19 (tightest lockstitch) or #20 (for very dense material, like thick webbing or hard leather) needle with #92 (T90) bonded thread. A #22 needle is reasonable for sewing with #138 into leather, unless it is hard. Then, move up to a #23.