Tension adjustment transitioning from multiple layers of leather to a single layer

[jayl65]

I’m researching cylinder arm clones like the Cobra 26 and Techsew 4800. I’ve noticed on YouTube videos that on a Cobra 26 the user stopped to adjust the bobbin tension when approaching the transition from a double layer of 5oz leather to a single layer. Then reversed the process when transitioning back. This seems like overkill to me. I’ve been a professional tailor for over 25 years and have never needed to do such a thing. The machine’s tension plates always did it automatically. Is this a common practice or a precautionary detail that is unnecessary? And does the Techsew with the height adjustment need this accommodation? I don’t want to purchase an industrial machine that requires so much adjustment during the building process. 

[Wizcrafts]

I've been sewing leather since 1984. My Father had a tailor shop for over 6 decades and he only owned one sewing machine: a Singer 31-15. Once he set the tensions, he was good to go. But, he only sewed cloth.

Armed with this history, my first industrial sewing machine was a straight stitch Singer 96k40. I bought it to sew a leather vest that i was constructing from a pattern and leather that I bought at my local Tandy Leather store. After gluing the varipus pieces together I began sewing across some back seams. The moment the foot encountered a new layer, it stopped in its tracks. When I used the knee lever to lift the foot, the stitch tension got screwed up, then the needles broke. I went back to that dealer with the vest in hand and he sold me a Singer walking foot head only. It dropped into the same table. That machine sewed the vest without any hiccups or readjustments. It was the old style spring foot mechanism with an oscillating horizontal hook.

Decades have passed since then, and I now have a shop full of walking foot machines. The absolute best one for climbing up and down while maintaining good knot placement is a Cowboy CB4500. The next in line is an Adler 30-7 patcher with a top feed walking foot that turns 360 degrees to feed the work in any direction. The rest of my machines are compound feed walking foot machines. Some have issues changing to different layer and others are not so bad.

All of my machines have check springs with adjustments for tension, stopping position, and importantly, slack. When sewing thick seams, it is best to give the top thread more slack via the check spring adjuster. Most of my machines have a common round disk covering the check spring. There is a curved slot on the top area with a set screw that can be loosened and tightened to control the amount of slack in the top thread. If you are going from a single layer to a double layer, preset the adjuster for the maximum slack, then adjust the top tension to hide the knots well inside the single layer..You should get them drawn up to about the same depth when you come to the new layer.

While this holds true for moving UP to a new layer, it may or may not be the same going down. Sometimes, the first stitch or two will draw the knots right up on top of the bottom layer because the foot is not directly pressing down around the needle. Here's where using a compound feed machine excels. It has an inside alternating foot that pressed down directly around the needle. As long as that small foot makes hard contact with the bottom layer, the stitches should be properly buried.

Another bad thing that can happen when transitioning from a higher level to a lower one is that, without intimate presser foot contact, the bottom layer may lift up as the needle ascends. This not only throws off the knots, but causes skipped stitches because the thread loop on the needle dissolves before pickoff time..

[kgg]

2 hours ago, jayl65 said:

I’m researching cylinder arm clones like the Cobra 26 and Techsew 4800

The Cobra 26 is a hybrid clone of the older Juki LS-341 with what appears to be a Alder type bobbin assembly rather then a Juki style.

The Techsew 4800 is sort of a clone of the Juki LS-1342 expect it has the larger nose gauge of the Juki-LS-341. The large knob on the top of the machine changes the vertical stroke of the presser foot and walking foot (amount of alternating vertical movement).

@Wizcrafts has offered some excellent advise.

How thick are the seams you are planning on sewing / crossing over??

Where are you located??

kgg

[jayl65]

Thanks Wizcrafts and kgg. I’m new here and don’t quite know how to respond to individuals or quote yet. I’m located in South Carolina and will primarily be sewing handbags,totes etc in Veg tan leather, waxed canvas and cork in the 5 to 10 oz weight. I currently have an old Singer 111w155 that I’m using. It sews great. I just need a cylinder arm. I collect sewing machines. Especially domestic 1st editions. I currently own about 30 machines ,but most are domestic with 4 industrials. I retired from costuming in the theater,film,opera and dance world where I was a dressmaker and tailor for over 30 years.  I don’t want to be bothered with peoples body image and fit issues any longer so this new endeavor will occupy me and not have to deal with folks insecurities about their bodies. 
 

I’d typically be sewing a double layer of 5 oz veg tan leather transitioning to a single layer. I just don’t want to stop every time I get to a transition to change the bobbin tension. I’ve never had to do that in my career and don’t want to make a mistake purchasing an industrial machine that requires that much attention. 
 

I’ll look into the Cowboy machine. I live in a rural area so I’d have to travel to test any machine I decide to pursue. I do have a Cobra dealer about 1 1/2 hour drive away. But the user in the video I watched was using a Cobra 26 and was changing the bobbin tension at each new transition. That’s why I was trying to avoid them. 

[Wizcrafts]

54 minutes ago, jayl65 said:

I’d typically be sewing a double layer of 5 oz veg tan leather transitioning to a single layer. I just don’t want to stop every time I get to a transition to change the bobbin tension.

@jayl65

There are some walking foot machines that have a large knob on the top that alters the foot lift amount and ratio, from low to high. A machine like this would let you set it to extend the inside foot all the way down when you drop to a single layer, thus pressing down directly around the needle to get perfectly balanced stitches at the transitions. The trick is to set the inside foot position so that it makes contact with the top of the leather at the same time as the point of the needle. The closer these two things are, the better the results.

[jayl65]

14 minutes ago, Wizcrafts said:

@jayl65

There are some walking foot machines that have a large knob on the top that alters the foot lift amount and ratio, from low to high. A machine like this would let you set it to extend the inside foot all the way down when you drop to a single layer, thus pressing down directly around the needle to get perfectly balanced stitches at the transitions. 

This is why I was looking at the Techsew 4800 for this capability. Wasn’t sure if it would solve the issue or just allow me to adjust the pressure foot height to climb up on the transitions. The leather I’m using isn’t heavy saddle weight. It’s more fashion oriented. The transitions are minimal compared to harness and saddle making. 

[kgg]

6 hours ago, jayl65 said:

I live in a rural area so I’d have to travel to test any machine I decide to pursue.

 

5 hours ago, jayl65 said:

This is why I was looking at the Techsew 4800 for this capability.

The cost difference between a brand name like Juki, PFAFF, Alder and a clone is going to be substantial ($2500 vs $5000+) so traveling to test ride a machine is a great plan as this is going to be an expensive outlay of cash. When you go to visit a vendor bring along some samples of leather you would be sewing with the thread size you would like. Hopefully the vendor has a LS-1341 there as well so you can compare it to a LS-1342 as you may decide you can do without the lift feature and save some dollars.

All the machines in the 341 class will handle V138 and some claim to be able to use V207 in 3/8" plus thickness. Once you are at or above the 1/2" thickness consistently you probably should consider a Class 441 machine like a Juki TSC-441 or clone like a Cowboy 4500, Cobra Class 4 to name a couple.

There are many clones of the Juki LS-1342 and another option maybe something like a Thor GC-1341 ( https://sunnysewingcenter.com/index.php/product/thor-gc-1341-cylinder-arm-walking-foot-sewing-machine-for-leather-upholstery-and-heavy-weight-materials/ ).

A couple of reference charts:

Leather weight to Thickness: https://www.weaverleathersupply.com/pages/leather-thickness?srsltid=AfmBOopqG07GeZKU1T96bRXTs1dHSx0rvBmYIep5bJEKUcl3ltioJRUZ

Needle size vs Thread size: https://www.tolindsewmach.com/thread-chart.html

If you want to reference someone type the "@" symbol then type a letter of the persons user name, a list will appear and then just click on the persons user name in the list.

kgg

 

[TomE]

Another key to feeding variabile thickness is your preparation of the transitions - skiving to create gradual changes in thickness.  For 5 oz leather handbags, a bell skiver would be useful to ease the transitions at seams and junctions.  The Class 26 (341 type clone) is a great climber in my experience. Makers Leather Supply has a lot of tutorials and patterns for handbags.  I mostly sew heavier straps on a 441 type machine.  I will add a wedge-shaped welt to the returns where the strap wraps around hardware, and skive the end of the strap to create a smooth transition.  I've also found that the narrow throat plates and pressor feet that are available for 441 type machines (search these forums) provide stability and do a good job climbing a transition.  The type of leather also matters.  I mostly use thick bridle and harness leathers that are waxy, causing material to slip if you're not careful feeding it.