Dumbing down a Cowboy CB4500, Cobra Class 4, or similar harness stitcher

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When it comes to sewing leather the best results are achieved with an industrial, compound feed walking foot sewing machine (e.g., upholstery sewing machines). The thicker the leather and heavier the thread, the bigger the machine must be. The largest leather sewing machines are called harness stitchers. These beasts are much heavier than standard upholstery sewing machines, having much stronger take-up cranks and levers and heavier tension and pressure springs.

Most people who buy the large harness stitchers, often called 441 clones (after the Juki TSC-441), use them to sew handgun holsters, knife sheathes, saddles, harnesses and saddle bags. These machines are able to sew at least 3/4 inch of veg-tan leather. They normally come preloaded with #277 bonded nylon thread, on top and in the bobbin and are adjusted and sewn off with this thread, with the test piece under the feet. Leatherworker.net has a forum dedicated to discussions about leather sewing machines. The most common brands and models discussed on Leatherworker.net include the Cowboy CB4500, the Cobra Class 4, and the Techsew 5100.

Nowadays, it seems that every leathercrafter who has worn out their hands with hand sewing their goods wants to buy that one sewing machine that does it all. They want it to sew wallet interiors, chaps, knife sheathes, tow straps, harnesses and extra thick gun holsters. I see them posting questions about which machine should I buy (to do all this), or similar wording. Respondents usually point out the fact that the typical upholstery grade walking foot sewing machines cannot sew thick holsters or use heavier thread than medium weight #138. The buyer will have to look at a more substantial machine, like a Cowboy, Cobra or Techsew, etc.

Most advice given is to buy more machine than you think you will need. So, the newbie to machine sewing shells out between $2000 to $3000 for a 441 clone (or $6000 for an actual Juki 441) expecting it to sew everything from wallet interiors to hand gun holsters. It sews the holsters just fine, but not the wallets or other thin projects. The knots are too big to hide between the thin leather layers. Pretty soon, they begin posting requests for help getting their (insert brand name and model) 441 super heavy duty stitcher to sew thin stuff. That's when they are told that they need to buy a lesser machine for thin work. Say what? I thought y'all said to buy more machine than I needed!

Some folks can and some can't afford to buy a second industrial sewing machine and table for thin work. Their other half (or they themselves) may own a domestic sewing machine, but they found it horrible at feeding and sewing leather, even wallets. They can't justify spending another thousand dollars for a lesser walking foot machine right now. What can they do if all they own is a 441 type machine? In these cases it is possible to "dumb down your machine" to get it to sew thin leather with thinner thread than it was built for. Here's how.

I'll use my Cowboy CB4500 as the reference, since that's what I currently own. Let's see how to dumb it down to sew thin stuff with thin thread.

First, buy some #19 (or even #20) needles in System 7x3. These are not leather point but are a good fit with #92 thread. There aren't usually any leather points available in System 794 under size 23/160. This is both a matter of economics and the tendency of these extra long needles to bend too easily below size 23/160.

Also buy #92 bonded nylon thread in the colors you intend to use (two spools of each color - one for the bobbin and one for the top thread). I usually get bobbins, oil, needles and thread from the dealer who sold me my machine. Order some extra bobbins if all of yours are already loaded with thick thread.

  1. Install a #19 or 20 needle (with the scarf facing to the right). Any other size will be either too tight or too loose for this thread.
  2. Thread the top with #92 bonded thread, but don't loop it around the top post. Feed it through just one hole. The extra tension from wrapping the thread around two holes in the top post could make it impossible to sink the knots effectively!
  3. Wind an empty bobbin with the color of #92 thread to be used on the bottom of the wallets or interiors, or chaps, etc.
  4. The bobbin spring will be way too loose if the last bobbin had #207 or larger thread in it. so, tighten it down to get a decent amount of tension of the bobbin thread, but not so much that the thin leather puckers on the bottom.
  5. Note: you may have to first loosen the long bobbin tension locking screw before the tensioning screw can be turned.
  6. Set the stitch length to about 6 or 7 stitches per inch.
  7. Run a test stitch line on a stack of the same thickness of leather/material as the interior, or whatever you are going to sew.
  8. Back off the top tension adjuster until the knots move down. You may also have to back off the bottom tension thumb nut so the bottom roller turns with the thread wrapped around it.
  9. If the knots still won't drop between the layers, you'll need to loosen the tension on the check spring. This spring is normally set to high tension action to work with the much heavier #277 or #346 thread that the machine was built to handle.
  10. Loosening the check spring action requires one of the open ended metric wrenches (11 or 12 mm?) that came with your CB4500 to loosen the nut on the back of the left end of the head, where the check spring shaft is fastened. This is a tricky tight fit and may require dinking with the position of the wrench to loosen that nut.
  11. With the locking nut backed off a thread or two, use a screwdriver blade on the front side to turn the bottom roller/check spring shaft counterclockwise until the spring loses some of its tension. Find a position where the spring travels all the way up and just makes it all the way down to the bottom travel stopper, then tighten down the locking nut. The check spring should have enough range of motion to hold the top thread taut until the needle has fully penetrated the leather.
  12. Sew some test stitches again. If the knots are still too close to the top surface, either back off the top tensioner all the way, or tighten the bobbin spring a little more, until they are submerged between the layers. Make sure that your top thread is feeding freely to the top tension disks!

These are the basic steps needed to dumb down a big Cowboy, Cobra, Techsew, Juki 441, or any other brand name 441 clone.

It is possible, even after you do all these steps, that the huge needle hole in the feed dog and oversize rectangular slot in the standard throat plate may let the thin or soft leather get pushed down inside the plate, or the feed dog itself. This might ruin your work, or cause gathering and tiny stitches. There is a solution though. If your machine came with an accessory flat throat plate with a narrow slot, you can remove the standard plate and feed dog and instead, use just the slotted plate. It is much less likely to allow the leather to be pushed into it. However, since you are taking the bottom feed dog out of the equation, your stitch length will change and reverse stitches may not hit the same holes unless you play with the stitch length lever as you sew backwards. If you didn't get this plate with the machine, you can order one from the dealer who sells that brand and model (to avoid possibly mismatched mounting holes).

I have done this temporary conversion many times, and it is always a PITA. Whenever possible, I use a different machine that is already setup with #69 or #92 thread and has shorter needles that don't deflect as easily. The System 7x3 and 794 needles used in the 441 class machines are over 2.5" long (~68 to 69 mm) and the thinner sizes deflect very easily when there are lumps or thick or hardened seams in the layers Then POP goes the needle!

UPDATE, 7/15/2020:

I have been in some discussions with new members on Leatherworker.net who can only afford one machine to sew everything from vests and wallets to holsters and knife sheathes. The machine that comes up in a lot of these topics is the Cowboy CB3200. Although this model is purposely limited to sewing 1/2 inch of leather, with up to #346 bonded thread, it is still based upon the Juki 441, making it fall into the same build category as the CB4500 and Cobra Class 4. In other words, it has beefed up take-up and tensioning components needed to sew thick leather with heavy thread and large needles that are beyond the capacity of most upholstery class walking foot machines.

One new member was wanting to mostly sew thin work, under 3/16 inch, with #69 and #92 thread, then occasionally sew 3/8 inch jobs with #277 or #346 thread. Presently, he can only afford one sewing machine. The advise I gave him was to buy the CB3200 clone he was asking about and dumb it down using the instructions in this article, then operate it in dumbed down mode by default. Leaving it dumbed down will give him ample time to fine tune the tensions and foot pressure for work that is normally below its optimum thickness. When he needs to sew something thicker, with heavier thread, he can do the opposite procedure with the tensions, needle and thread and smarten up the machine.

Smartening up a 441 class sewing machine for occasional heavy sewing restores it to its native capabilities and sweet spots. If one will be sewing thin work most of the time and only needs to beef it up occasionally, and can only afford one machine, this system will do until purchasing another lighter duty machine for the thinner work can be justified. It's not ideal, but is doable!

Wrapping up...

Dumbing down your 441 heavy leather sewing machine to sew thin projects may earn you enough money to buy an advanced upholstery grade walking foot sewing machine (the type that maxes out at 3/8" and #138 or #207 thread). Having more than one machine will greatly expand your sewing possibilities.

You can look over a wide range of Industrial Walking Foot Sewing Machines here.

3 Comments

If you're doing a big run of thin wallets/bags/clutches, this information is invaluable. If you're going to do this every once in a while, it would still be worth the adjustments. If you swap from heavy duty to medium/light duty daily, a second machine is probably more beneficial. But thank you for taking the time to explain this and for doing the leg work on finding tension adjustments.

Thanks

Excellent information. Thanks.

Regarding work on thin leather, where something like a Cowboy CB4500 (or similar clone) is too heavy a machine and a domestic sewing machine is too lightweight, a great solution for a 3rd machine (that we have) is a Sailrite Ultrafeed LSZ-1 (BLUE). But don't skimp the $100 to get the cheaper RED model that lacks zigzag--you will regret it. The Sailrite LSZ-1 is terrific for a range of mid-weight fabric tasks.

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This page contains a single entry by Wiz published on February 1, 2019 12:37 PM.

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