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The Type Of Sewing Machine You Need To Sew Leather


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#1 Wizcrafts

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Posted 10 July 2010 - 06:30 PM

Content to be added and updated on an ongoing basis.

Welcome to the Leatherworker.net Leather Sewing Machines Forum! If you are new to this forum and you are seeking information about the right type of sewing machine you'll need to sew leather, you're in the right place. Everything stated below is either my honest opinion, or the honest opinions of other members of this forum. We all have personal hands-on experience sewing a broad range of leather projects on a broad range of sewing machines. Most of us have worked our way up, trying different machines, fixing up old ones, modifying them, tricking them out, all in usually fruitless efforts to sew something they are simply not capable of sewing. This is especially true when it comes to sewing leather.

Leather varies in texture, weight, stickiness, thickness, density, dryness and chemical composition. No doubt, some of you have seen pictures and videos online, showing this or that machine sewing leather. Those pictures are uploaded by the seller of the machine, to broaden their purchasing audience. What many first time sewers don't realize, is that just because a particular machine is said to be able to "sew leather," that does not mean it will do it well for the types of leather the buyer wants to sew. Leather varies, as stated above. The machines that can sew garment weight leather may not be able to sew chaps, belts, tack, holsters, or saddle bags. Just because a machine is large, or metal bodied, or or even industrial, does not make it a true leather sewing machine!

First, I will address the machines seen on eBay, sold as Industrial Strength sewing machines. Most are all metal and proudly state that fact. The sellers talk about the "powerful" 1.2 or 1.5 amp motors that are attached. Some even have ribbed drive belts and gear reduction, to eliminate slippage when sewing thick material. No doubt these are strong machines. I have a few myself. I have 2 old iron body Singers and a metal body Kenmore, even an ancient White Rotary machine. Will they sew leather? Yes, two layers of 2 to 4 oz garment leather. Will they sew leather with nylon thread? Yes, but no bigger than #69 nylon. Will they smoothly feed garment leather as it is sewn? Yes, as long as it is fairly small in size and weight and not stitcky on the top grain. If the top is sticky, no way, Jose. Sticky vinyl and leather usually gets dragged back by the top pressor foot and the stitches are either too short, or filigree the material, or skip frequently.

Sticky material, like smooth top grain chrome tanned garment leather and Naugahyde (vinyl), does not feed evenly unless the pressure on the "pressor foot" is reduced significantly. All of the feeding is done from the bottom, by the teeth in what are know as "feed dogs." The pressor foot has to apply enough pressure to the top of the material to keep it from moving between stitches and also to prevent it from lifting with the needle, as the needle begins its ascent. This is when the thread in the needle's eye forms a loop for the rotating or oscillating "shuttle" pickup point to grab. The grabbed top thread is then pulled around the bobbin case and bobbin thread, which is pulled up by the lifting take-up lever, to create the lockstitch inside the material. If the top pressure is insufficient for the thickness and density of material being sewn, the material will lift with the ascending needle and top thread. When this happens the loop may not be formed and there will be skipped stitches. Even if the material is held down by the foot to form the stitches, the spring pressure may not be enough to hold down dense veg-tan leather when the take-up lever lifts up. If the leather lifts during the take-up phase the stitch length will vary wildly, the layers may slide out of alignment and the needle may deflect and break. This can also cause skipped stitches.

In an effort to overcome the problem of feeding sticky vinyl and leather, sewing machine companies and aftermarket manufacturers produce add on pressor feet to make it easier to feed these materials. Some dealers sell replacement feet with little rollers inside them (roller feet), or teflon plastic feet that claim to allow sticky material to feed better that steel feet. Others sell actual rolling wheel pressor foot attachments and sets, where the foot, feed dog and throat cover plate are replaced as a group. Finally, you can usually find a replacement foot called an "even feed" foot, or "walking foot" attachment. It contains an inner and outer pressor foot, which alternate up and down as the needle moves up and down. This is done by a lever that is hooked on top of the needle screw on the needle bar. The inner foot presses down and moves as the needle lifts out of the material and the feed dogs pull the material back. When the feed dogs reach the preset stitch length they drop down (drop feed) and the inside foot lifts up with the raised needle bar and snaps forward. The outer foot then drops to hold the material in place until the needle has penetrated the work again and is ready to form the next stitch.

This is not a true walking foot, as is used in true walking foot machines. It is an effort to improve the feeding ability of the wrong machine for the job. An add-on walking foot will not actually help you feed heavy garments or chaps through the machine, but it will allow the leather or vinyl to move and stitch without stitcking to the bottom of the pressor foot, allowing you to increase the pressure to prevent lifting, shortened stitches, or skipped stitches. If the material being sewn is long and wide, or heavy, your machine will have trouble pulling it back to form the stitches, despite having the even feed attachment installed. There are no teeth on the bottom of the pressor feet and the material can slide easily with a little tug, or from the weight of the work folding over the front of the work table.

I have learned that these even feed attachments usually reduce the clearance under the feet. This means you cannot sew as much thickness as with the standard foot. If you raise the pressor foot bar for more clearance, the needle bar, or top thread guide on the bottom of the needle bar will hit the inner pressor foot. They are a compromise feed system.

Even if you are able to feed the material through an industrial strength sewing machine, you are going to be limited in the thickness that it can sew, as well as the size of thread it can handle and the sizes of needle it can use. Number 69 bonded nylon thread is fine for leather vests or small vinyl projects, but is not so good for upholstery or chaps, or anything thicker, like belts and bags. For these projects, you'll want to use at least twice the size of thread: #138. At this point, most home machines drop out of the picture. Even a lot of actual industrial machines will not sew with #138 or larger nylon thread. They might be able to sew soft polyester or cotton thread in larger sizes, often sold a button or topstitch thread.

To properly sew leather you need an actual Walking Foot sewing machine. In my next installment I will define the various types of walking foot machines and what makes a dedicated leather stitcher different from a leather-capable sewing machine. I have to go earn my keep now, but maybe some other members will add to this topic.

Later!

Barra; Joanne; can this become a Sticky topic?

Edited by Johanna, 10 July 2010 - 09:05 PM.
turned into a sticky- thanks Whiz!!!

Posted IMHO, by Wiz

#2 outcast

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Posted 10 July 2010 - 08:57 PM

This is good stuff. I look forward to more.
Steve


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#3 Wizcrafts

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Posted 11 July 2010 - 03:50 PM

When I left off my last post in this thread, I said that I would define the various types of "walking foot" sewing machines. So, here I go!

The home and industrial strength sewing machines I wrote about yesterday all come equipped with flat, static "pressor" feet (the foot shaped steel plate that presses down on the material and applies pressure). I detailed about how a steel pressor foot drags sticky material, causing shortened stitches and showed some optional replacement feet that assist the machines in moving leather and vinyl material properly. This ended with my statement that I recommended a true walking foot machine for sewing leather, rather than a converted flat foot, straight stitch machine. A straight stitch machine does not have zig-zag capabilities and is usually equipped with a flat pressor foot and the work is driven entirely by the bottom feed dogs.

The difference between flat foot, bottom feed (feed dogs), straight stitch machines and walking foot machines is profound. A walking foot machine may have any of the following drive configurations and still fit the walking foot classification.
  • Compound/triple feed: the feed dog, needle and inside pressor foot all move together, in synchronization. BEST OVERALL SYSTEM
  • Double feed: The feed dog and outer pressor foot move together in synchronization. GOOD FOR VINYL & NON-MARKABLE LEATHER
  • Jump feed: The needle moves the work as the slotted pressor foot lifts (with or without a dull tooth or smooth feed dog). BEST FOR HARNESSES, HALTERS AND HOLSTERS
  • Pressor foot feed: Used by all shoe patchers, the pressor foot has teeth on the bottom that move the work. WILL MARK VEG-TAN AND BRIDLE LEATHER
  • Snap feed: The feed dog pulls from the bottom while the outer foot pivots on a spring loaded hinge. When the feed dog drops, the outer foot lifts and snaps forward. GOOD FOR BUFFING WHEELS, CAR WASH CLOTHS
Of these types of machine I find #1 to be the best overall machine for a variety of leather and vinyl sewing. The triple feed mechanism ensures that there is no slippage of the layers of material (the needle moves the work with the feed dog), the alternating feet will walk over seams and back down, you can apply as much top pressure as needed to keep the material from lifting and it still feeds properly and you can hold the material fairly tight and it will still feed and give the desired stitch length (unless there is too much slack in the drive system).

The double feed system, #2, is typically used in portable walking foot machines that are designed for and sold to the marine vinyl repair industry. The teeth on the bottom of the outer foot move in time with the feed dogs and provide great traction on otherwise slippery and large vinyl boat and seat covers. However, these teeth will mark veg-tan and bridle leather pretty badly.

Type 3, the jump foot, is the harness makers choice. These machines may or may not have a smooth feed dog underneath, but always have a moving needle and slotted single pressor foot. When the needle penetrates the leather the pressor foot lifts up, then the needle moves the work back according to the preset stitch length. As the needle begins to lift, the foot comes down to secure the work against unwanted movement, or lifting, from a hot needle and thick thread. A sub-category of these machines includes needle and awl machines (more on that later on).

The pressor foot drive in the shoe patchers is meant for patching shoes, boots, zippers, holes in garments and handles on bags. The teeth under the foot are fairly aggressive and will create deep marks in veg-tan and bridle leather. Despite this, a lot of leathercrafters use shoe patchers for a lot of their projects. The real problem with patchers is the typically tiny bobbin they have, although certain models have a larger, double capacity bobbin.

Finally, the snap feed system is not much use when sewing any slick or waxy leather surface. This feed system was stock on the Singer 132K6 machines. I had one early in my sewing history and thought it was the cat's meow. That is, until I tried to sew the edges of a hand stamped and carnauba creamed veg-tan belt. The snapping top foot let the belt slide forward between stitches as it slipped forward prematurely, causing the stitches to vary in length all over the place. It did a good job feeding soft or roughed up leather and buffing wheels, but had a hard time feeding smooth grain leather. I don't recommend these machines for sewing most leather projects.

Interestingly, the snap feed system in the Singer 132k6 is the same principle used in the even feed attachments for the so-called "industrial strength" home sewing machines.

Aside from the snap foot system, which has trouble feeding slick top grain leather, all of the other walking foot systems provide a solid feeding system, with adequate top pressure to allow the operator to control the work as it enters the needle area. If you are stitching a large leather seat cover, a walking foot, compound feed machine will provide the best control and drive to pull the material through the work area, even if it is long and folded over the front of the table, or hangs around nose of a cylinder arm machine. All you need to do is make sure the material feeds the correct distance in from the edge and doesn't fall off the left side of the arm, or needle area. An edge guide really helps to stitch a defined distance in from the edge. You just need to hold or clamp the layers together and press them against the right side edge guide. The walking feet and moving needle do the rest!

If you intend to sew harness, halters, bridles, sheathes and holsters, a narrow slotted jump foot machine is the best for these jobs. Some machines offer optional feet that only have one left or right "toe" - rather than the slotted double toe. With a right toe jump foot you can sew right up to the raised edge of a molded case, or holster, from the top side. Also, since these machines either have no feed dog, or a totally smooth bottom feeder, they do no create tooth marks on the back side of the leather. This is especially important if you want to produce show harness and commercial holsters and Police gear.

In my next installment I will provide some pictures of these different types of walking foot machines.

Note, that I have not addressed the amount of clearance under the pressor feet yet. This is because that figure varies with various brands and the way they have been equipped by the seller. Most walking foot flat table machines will sew up to 3/8" of leather. Some machines are capable of sewing 1/2" and others, 3/4" and more.

Time to go to work. Lee Ya Sater folks!
Posted IMHO, by Wiz

#4 Techsew Ron

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Posted 12 July 2010 - 10:01 AM

Great job so far, Wiz!

Ron
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#5 Wizcrafts

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Posted 12 July 2010 - 10:36 AM

Great job so far, Wiz!

Ron

Thanks Ron! May I link to some of your videos in this article?
Posted IMHO, by Wiz

#6 Cobra Steve

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Posted 12 July 2010 - 10:54 AM

Thanks Ron! May I link to some of your videos in this article?



Great job, Wiz. Steve
Thank You
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http://www.leathermachineco.com
cobra@leathermachineco.com

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#7 Johanna

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Posted 12 July 2010 - 11:27 AM

Click on Ronnie's (Techsew) or Steve's (Cobra) banners on the top of the page- they have both made their videos available to anyone interested. Anyone that wants to make more videos is welcome to post them here on LW. We've got plenty of bandwidth, and lots of interested people.

Whiz, Posted Image Thank you for this. All the sewing machine guys are cheering you, and that tells me all I need to know about the accuracy of the info. You are helping people now and in the future by explaining in plain English the mysteries of leather sewing machines, and we appreciate the time and effort you're putting into the series.
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#8 Techsew Ron

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Posted 12 July 2010 - 02:00 PM

Thanks Ron! May I link to some of your videos in this article?


No problem! All demo and instructional videos are located on our YouTube channel: http://www.youtube.c...haelsewingVIDEO

Ron
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#9 Wizcrafts

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Posted 16 July 2010 - 01:27 PM

I have finally managed to take a series of photos and reduce them enough to be able to post several in one reply. The following photos are from my National 300N heavy duty walking foot machine. Similar to a Consew 206RB, it is capable of sewing a little over 3/8", depending on the density of the leather and needle and thread sizes. It handles a range of thread from #69, up to #207 - bonded nylon or polyester. It takes series 135x needles from #14 (smaller available, but not recommended), up to #25, max. These photos show it with a #22 leather point needle and #138 Weaver nylon thread (messy), which was used to sew suede lined guitar straps and rifle slings.

This is a serious leather and vinyl sewing machine! I have replaced the clutch motor with a servo motor I bought from Bob Kovar, at Toledo Industrial Sewing Machines. It is geared down internally and has a 2" pulley. It produces the equivalent power of a 1/2 to 3/4 hp clutch motor and has a top speed of 1500 rpm. The motor draws no power until you apply the floor pedal to it.

One more thing, the bobbins on this type of walking foot machine are known as M style bobbins and are 1 inch in diameter. They have a higher thread carrying capacity than standard industrial machine bobbins.

Walking Foot sewing machine, with compound, triple feed.

Attached File  IMG_0001.jpg   105.52KB   2927 downloads Attached File  IMG_0005.jpg   127.45KB   3107 downloads Attached File  IMG_0019.jpg   112.91KB   2639 downloads Attached File  IMG_0020.jpg   119.34KB   2456 downloads Attached File  IMG_0021.jpg   114.56KB   2283 downloads Attached File  IMG_0030.jpg   88.7KB   2232 downloads Attached File  IMG_0033b.jpg   92.04KB   2156 downloads Attached File  IMG_0037.jpg   76.66KB   2279 downloads

Attached File  IMG_0043.jpg   110.17KB   2985 downloads More pressor feet (inner and outer sets) for a compound feed walking foot machine. These are known as 111 series feet, named after the famous Singer 111 walking foot machines, of antiquity (but still in service!). If there is a job to be done that needs a special foot, you can find one for any industrial machine that uses series 111 pressor feet.

Attached File  IMG_0078.jpg   347.91KB   2857 downloads Last, but not least, here is a close-up, left side view, of my Union Lockstitch needle and awl stitcher sewing about 50 ounces of hard belt leather. The top of the needle is barbed. The thread is fed into the barb through a thread guide and looper arm, that revolves around the lifted needle. The needle then goes down, where a revolving pickup point grabs the loop off the barb, under the throat plate, and carries it around the bobbin shuttle. This machine is capable of some very serious sewing! The photo shows it threaded with #277 bonded nylon, top and bottom, which is in the low range of the weights it can manage. I have sewn with #550 thread on a Union Lockstitch machine!

Edited by Wizcrafts, 16 July 2010 - 01:44 PM.

Posted IMHO, by Wiz

#10 Wizcrafts

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Posted 16 July 2010 - 02:39 PM

For those of you who are just getting into sewing leather, or are about to move up from a home sewing machine, here is a comparison of the bobbins used in various types of sewing machines.

Attached File  array-of-bobbins2.jpg   70.88KB   1094 downloads

From left to right, front row, we have:
  • Small bobbin shoe patcher (Singer 29-4 and most K series)
  • Large bobbin shoe patcher (Singer 29k172, etc)
  • Class 66 home sewing machine bobbin
  • Class 15 and standard industrial or Kenmore bobbin
  • Large M bobbin
Finally, in the back, is a bobbin for a Union Lockstitch Machine.

Attached File  #69+#207-thread.jpg   68.36KB   1009 downloads Here is a comparison of a spool of #207 vs #69 nylon thread (1 pound vs 1/4 pound). The #69 thread works in most home and straight stitch, static pressor foot, drop feed industrial sewing machines, with a #16 or #18 needle. To use #207 requires a very heavy duty machine, with a BIG motor, and a #25 needle.

When you are choosing a sewing machine, don't just select it because of its price, or local availability, check out its needle, thread and bobbin size capacities.
Posted IMHO, by Wiz

#11 Wizcrafts

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Posted 16 July 2010 - 03:12 PM

This ditty is about the different types of pressor feet used on home and industrial sewing machines. Using the right foot makes your work feed and stitch better than is otherwise going to be the case. These photos will give you a frame of reference.

First, here is a picture of the standard static (flat) pressor foot used on a Kenmore home, or straight-stitch industrial sewing machine:
Attached File  flat-pfoot.jpg   3KB   471 downloads This is what you get with most straight stitch garment machines. Most other home machines come with a straight stitch attachment foot. All older machines, up to the late 1950's tended to be straight stitch only and one needed to attach an add-on mechanism to sew a zig-zag or button hole stitch. Now, they are standard on most home machines and you can buy industrial zig-zag machines as well.

Here is a zig-zag pressor foot:
Attached File  IMG_0042.jpg   75.61KB   711 downloads

This is a cording or welting foot (straight stitch):
Attached File  IMG_0004.jpg   39.46KB   834 downloads

A roller foot makes it easier to feed sticky material, like vinyl and garment leather. Here is one inexpensive type of roller foot:
Attached File  roller-foot.jpg   4.59KB   1037 downloads

Here is what eBay sellers tell you is a walking foot, or even feed foot:
Attached File  IMG_0035.jpg   154.76KB   1657 downloads (kinda looks like an alien bug invader!)

This IS a walking foot:
Attached File  walking-foot.jpg   109.78KB   1715 downloads
Posted IMHO, by Wiz

#12 Wizcrafts

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Posted 16 July 2010 - 04:27 PM

What is the difference between an all metal, "industrial strength" sewing machine and an actual "industrial" machine? The first term is a favorite of eBay sellers to help move out old, refurbished clunkers and antiques. Tell somebody new to sewing that a heavy, all metal machine sews leather, show them a stack of dimes under the pressor foot and provide some photos and samples of the leather it can sew, and they will have all the sales they want.

Unfortunately for the buyers, most will not be able to sew the type of leather they bought that machine for. I frequently see nebies asking if the old SInger in this or that eBay ad will sew chaps, belts and holsters. It usually starts out with they only want to sew garment leather, but by the second reply the heavy stuff pops into their description. The thinking is understandable: that machine was advertised as being able to sew real leather. Yes, it can sew leather, but only thin garment or light chap leather and not without problems of dragging the top grain on the pressor foot.

I think that a picture is worth a thousand words, so here is one I took of my Industrial Strength Singer 15-91, fully rebuilt and setup to sew to its best capacity, next to my National 300N walking foot machine (equivalent to a Consew 206RB).

Attached File  IMG_0014.jpg   105.43KB   2480 downloads

Not in its wildest Robot Dreams will that 1953 Singer 15 class machine sew anything much thicker than 1/4", with thread no larger than #69 (maybe #92), without babying the material through the feed mechanism. I know; I tried. I had to install a walking foot attachment to get it to sew marine vinyl, two layers thick, because the material was dragging under the foot. This reduced the maximum clearance to under 1/4." Holding the material tight to keep it aligned caused it to change stitch length or break needles. Sewing leather was not a joy either, just a big hassle and more broken needles. The most aggtraving part of sewing with a home machine is the tiny motor that drives the mechanism was bogging down at startup and I had to hand-wheel to help to go. Most so-called "industrial strength" machines have a motor rated at about 1/10th to 1/15th horsepower, 75 to 150 watts.

When I finally got a-hold of the National 300N walking foot machine, it came with a 1/3 hp, 1725 rpm, 300 watt clutch motor. It was set-up for sewing upholstery and had a 3" pulley on the motor. It was difficult to control and I know how to operate clutch motors. A phone call to Toledo Industrial Sewing Machines cured that problem. He sold me a SewPro 500GR servo motor, with 3:1 built-in gear reduction and a 2" pulley; the equivalent of a 900 watt motor. I haven't had any control or penetration problems since. This machine will sew over 3/8" of actual leather belting or harness strapping. It uses needles up to number 25 and thread up to #207. I can control the servo morot at any speed, even less than 1 stitch per second.

Having the actual industrial walking foot machine allows one to hold back the work and it will still feed without changing stitch length, or popping needles from back tension. You can turn on more top pressure to keep thick and dense leather from lifting under the foot, causing skipped stitches. If you intend to sew everything from leather garments to belts, a real walking foot machine is the best way to go. The feed mechanism is too rough to use on light cloth garments, but works great on denim and vinyl. It walks over seams effortlessly.

That's all I have time for now. More to come later on.
Posted IMHO, by Wiz

#13 Wizcrafts

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Posted 17 July 2010 - 01:21 PM

This would be a good time to compare home vs industrial motors and needles. You depend on the turning power of the motor to get the first stitch into your material, and the horsepower determines how easy or hard that will be. Once it gets the machine sewing, almost any home style sewing motor will run a sewing machine at a decent rate of stitches per minute, up to its gearing limit. But, that speed is usually only attainable if you remain within the practical limits of material density, needle and thread size. The bigger the motor, and higher its horsepower rating, the more dense the material it can try to penetrate. Most industrial sewing machines come with either a clutch or servo motor, which is mounted under the work table, which the machine rests on top of. A v-belt connects the pulley on the motor to the pulley cast into the flywheel (handwheel) on the back of the machine.

Industrial sewing machines are usually fitted with a motor pulley that best suits the intended work. Upholsters and garment makers want high speed, so they order a large motor pulley, somewhere in the vicinity of 3 to 4 inches diameter, inside the groove. The pulley on the flywheel of garment machines is typically around 4 inches diameter, so these machines are often running at close to 1:1. Industrial clutch motors run at 1725 rpm, at 120 volts, or 3450 rpm at 220 volts (3-phase), so a machine running a 1:1 ration to the motor will sew at that speed. If you were to purchase a used garment sewing machine, even with a 120 volt motor, a 1:1 pulley ration may be uncontrollable for the untrained sewer. A smaller motor pulley is the answer to that problem.

Most leather sewing machines are equipped with a 2 inch motor pulley. This not only slows the machine down to a more controllable speed, but doubles the torque. This comes in as very important when you try to sew thick or dense leather, or bio-plastic projects, or plywood covered cases. Furthermore, if you sew anything other than garment/chap leather at the high speeds used in garment machines, the friction will heat the needle to almost red hot, melting the thread, scoring the leather and usually, causing the needle to grab inside the leather, on its way back up. This causes the leather to lift with the needle. When that happens at the moment the bobbin shuttle's pickup point is passing by the eye of the needle, you will get skipped stitches.

The bigger the machine, the thicker the intended payload, the larger the needle and thread it uses, the slower it must turn. Therefore, distributors of harness stitching machines often include a speed reducer between the motor and the machine. This reduction is at least 3:1, or more. I have an Adler flatbed harness stitcher that was so geared down and its maximum speed was about 3 stitches per second, or 180 per minute. It sure could punch through 3/4" of belt leather at that speed and gear ratio!

Now, on to the pictures. The first photo shows a home sewing machine motor next to a clutch motor. The home motor is rated at 75 watts and has a 1/2" pulley. The industrial motor is a 1/3 hp 300 watt motor, with a 2.25" pulley. The home motor is suitable for driving a home machine through cloth and denim. The industrial clutch motor can sew 3/8" of leather easily with that size pulley. A 2" pulley would give it even more torque.

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Clutch motors always run at full speed, but they develop their maximum torque when you engage the motor to the machine. You control them by means of a floor pedal, about a foot square, with a rod connecting it to a movable arm protruding down from the bottom of the motor. When you move your toe downwards on the pedal, the clutch begins to engage, turning the machine. Skilled sewers learn to control the motor from barely turning the machine, to full speed. This takes a bit of practice and the amount of toe required to feather the clutch often depends on the density of the material, and inertial resistance of the machine's mechanism. Also, since a clutch motor always runs at full speed, it always consumes electricity. When it runs under load, sewing, it consumes its rated power draw. Most industrial sewing motors come in these ratings, with the smallest meant for garment machines only:
  • 1/4 hp
  • 1/3 hp
  • 1/2 hp
  • 3/4hp
These motors have a 3/4" shaft and take pulleys made for them and the narrower, 7/16" v-belts they use.

In order to make sewing on industrial machines more controllable, and to reduce the cost of operating the machines on 110 volt circuits, servo control motors were developed. The early generation were prone to premature failure and made a lot of noise as they started up. This has been improved and in some cases, totally overcome, by new controller technologies. Industrial sewing servo motors are available in a range of power capacities from about 1/2, up to 3/4 horsepower. Their wattage ratings vary, from about 300, up to 600 w. The nice thing about all servo motors is that until you press down on the floor pedal, they do not draw more than 1 watt. You can leave a servo motor turned on all the time and not notice it in your electric bill, unless you are actively sewing a lot.

One of the shortcomings of many servo motors is a lack of startup torque. While they do produce their rated drive power at full speed, the opposite is true at slow speeds. That is another reason why many leather stitchers ship with a speed reducer pulley under the table. It doubles or triples the slow speed torque, while also reducing the maximum speed to one that won't burn up you leather and thread.

There is a new type of servo motor that has been produced, to overcome the problem of low slow speed torque. It is a gear reduction motor, currently marketed under the brand name "SewPro." I have their model 500GR. It features a 2" pulley and a speed limiter knob on the back. It runs at a maximum speed of 1500 rpm. This machine only consumes 300 watts flat out, but has a 3:1 reduction system, giving it the same power as most 3/4 hp servo motors. I have one and love it. I can sew from under 1 stitch per second, to about 10 to 12 stitches per second (depends on the diameter of the flywheel pulley). It is a bit low for upholstery, but not unacceptable. It is perfect for leather, which is what I mostly sew these days. It sews marine vinyl like it is butter.

Here is a picture of my SewPro 500GR servo motor, mounted under the table of my 75 pound National 300N walking foot machine:

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Next, let's compare a couple of needles. The one on the left is a #12 home sewing machine needle, used to sew thin cotton thread into shirts and pants. The needle on the right is a number 25 needle (series 135x16), used to sew up to #277 nylon thread into leather holsters and straps. Home style sewing needles are not usually available in sizes bigger than #18, although I found some #20 on eBay. Series 135x16 (leather point) and 135x17 (ball point) are available in sizes up to #25. As a reference, #69 nylon thread, commonly used in upholstery and marine vinyl sewing, uses a #18 to 20 needle. Stronger results are achieved with #135/138 nylon or polyester thread, which requires a #21 or #22 needle. This leaves out all home machines, including the ones sold on eBay as "industrial strength."

Here then, are the home and industrial needles, side by each:

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Now that you have seen comparisons of the motors and needles used by home and industrial sewing machines, you'll have a better understanding of what is required to sew leather.
Posted IMHO, by Wiz

#14 Wizcrafts

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Posted 19 July 2010 - 01:28 PM

This article is now being Tweeted on Twitter. Thanks all!

BTW: I am @Wizcrafts on Twitter. My tweets are mostly about computer and website security, malware threats and spam analysis, but I do make the occasional Tweet about my leather and sewing work.

Today is my birthday, so I probably won't be posting anything new today. I'll get back to this article later, or tomorrow. I know I have a contract sewing job to do sometime tomorrow. Maybe I'll shoot a couple of pix of my walking foot machine earning me some money. It may help someone who wants to sew similar leather projects.

I have shot a few movies of my machines, with my digital camera, but haven't figured out how to convert them from Apple .MOV files into WM .AVI files. I may see if YouTube has a converter and upload them there, for the world to see (in Flash format).
Posted IMHO, by Wiz

#15 CJ1

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Posted 19 July 2010 - 11:36 PM

Hallo,
I was just reading you post.very interesting. Maybe you want to take a look at Member CJs Leather Repair(my wife).She got an "old girl" posted you might wanna see.This machine is unbelievable.She goes through leather up to 1"thick and more...

Besides Happy Birthday..





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