“Disrespectful of Our Experts”
I was just kicked off a Yahoo sewing group because I was “disrespectful of our experts”. Now my disrespect, was in not agreeing with them, and doing many hours of research to find out if they or I were correct, and reporting the results which were inconclusive to the group.
Now they are totally correct, I am disrespectful of experts of that ilk. They are only self-styled. They are right and you are wrong if you do not agree with them. Facts have no meaning in their minds, only their unsupported opinions count.
I hope I never treat my readers that way, I try to pass on information that I think is correct. I am, like everyone else I ever met, not perfect I make mistakes. I admit that I like to argue sometimes. But I do not think that someone is wrong or bad because they disagree with me. I just think we do not agree.
I am rather upset by this. Any group or forum I join I try to participate and provide what info I have. I do not say things I do not think are true, but I can certainly be mistaken and probably often am. But I try to be a contributor, and not just someone that joins to get my question answered and leaves.
The actual result of this is that I have quit all Yahoo groups and I will no longer contribute anymore to sewing forums of any type other than this blog, where the editor (myself) hates but tolerates me (GRIN!). I tend to waste a lot of time on forums, so they probably did me a big favor.
Anyway if you have ever wondered why much you read on the ineternet in certain areas sounds like it is parroted by the same bird, I think this might explain some of it.
Just What I Needed
Just what I needed, another sewing machine. This one is a White Fair Lady from the 1960’s, model number 763. It is a straight stitch machine and quite different from the Singer, also seems to be in better condition. All it needed was cleaning, oiling, bobbins, a light bulb, and the bobbin tension adjusted a bit.
White Fair Lady Sewing Machine
I picked it up an a Goodwill Store out of town they other day for $25. It seems to sew nicely and it is a bit more powerful than the Singer, so it may be better for things like this case,
Tape Recorder Carry Case
I sewed up the other day on the Singer.
Turning your zig-zag machine into a straight stitch machine.
This could not be easier. You only need two accessories:
1. A straight stitch needle plate.
2. A straight stitch presser foot.
Zig-zag setup on left, straight stitch setup on right
I found them on eBay for my machine, actually for a slightly later model, but they both use the same accessories. My machine is a 337 as I have mentioned before, the parts I got are for a 348.
Remove the zig-zag plate
It is only a matter of removing the zig-zag presser foot, pulling open the bobbin cover, and removing the zig-zag needle plate, then installing the straight stitch plate and foot in the opposite order. Of course if you need to use zig-zag stitches you have to change things back to the zig-zag configuration.
Straight stitch plate and foot installed
Does it make much difference? I found the stitches are straighter, lacking that slightly slanted look, and the material does not get pulled slightly into the needle hole. As a result the machine seems to sew more smoothly.
Howto set your tension
I have seen many articles telling you what your seams should look like at the proper tension, but all of them have been really vague about how to go about adjusting the tension to get that seam.
First you need some kind of starting point. Older Singer machines were factory set to sew medium weight fabric with number 50 mercerized cotton thread and a number 14 needle with the tension dial set at 3. Nowadays that needs some explanation. As far as I can determine by medium weight fabric they mean something like a man’s dress shirt is made from. For thread I am using Coats & Clark Duly Duty Plus Polyester. I think it is a bit heavier than #50 cotton size wise (I am not real sure of that as I can not find any cotton thread around here to compare it to), but Poly stretches a bit so you usually use a slightly lower tension, because of that it seems to be about right. I also picked up some #12 Schmitz Sharp needles. Anyway I set my machine up so the dial is at 3 with that combination, and it seems to give a good range of setting for other thread and needles.
A side note: I said in the article about Needles, Thread, Fabric and Tension that all of them make a difference. With a bit more experience I now think the most important thing is to match your needle to your fabric. I found that medium heavy Duck breaks #11, and bends number 14 needles, but works fine with #16 needles. At the moment I am using #12 and #16 sharp point needles for most everything.
Now to the matter at hand, how to go about setting your tension when you have no idea what is going to be correct. Start with the dial set at 3 or the center of the dial if you have no idea what the machine is set for. Run a bit of a seam on a piece of dress shirt weight fabric folded double, a couple of inches is enough. I suggest marking one side so you can easily tell which side is the top. Examine the seam.
Step One:
If there are loops on top reduce your tension two dial marks.
If there are loops on the bottom increase the tension two dial marks
If there are no loops go to the next step
Step Two:
If it looks like sewing on the bottom, and just a straight thread on top, increase your tension one mark.
If it looks like sewing on top, and just a straight thread on bottom reduce your tension one mark.
If it looks like sewing on both sides go to the next step.
Step Three:
Look very carefully at the stitching,
If it looks loose on the bottom increase the tension ½ the amount you changed it the last time.
If it looks loose on the top reduce the tension ½ the amount you changed it the last time.
Repeat until you can not tell any difference in the two threads.
You programmer types will recognize that we and using a binary search to find the correct tension setting. For others what that means is we are moving the setting past what it needs to be and then back half way. We are reducing the error 50% or more each time we do that. Going from loopy to good enough only takes five steps; 2, 1, ½, ¼, 1/8. A couple of steps more and you are moving the dial only a hair and have it about as close at a really well set up machine will do because there is some slop in the train and it will wobble that much. You will also notice that correct tension is only about 1/8 a dial marking from incorrect.
Make notes of what is correct with each needle/thread combination you use, and you will be able to set the dial close next time you use that combination. From there it only takes one or two steps to get it just right.
New look
I am working at making this blog a bit better thus the new theme. Really wanted something in beige, but could not find anything that appealed to me. So I went with the same theme I am using on Subject to Change. It is called Emptiness.
That is my old junk sewing machine up at the top, on the kitchen table. I look at the photo, and say to myself, “I really need to refinish that top-plate”. Actually it does not look that bad in real life.
I think I have the tension problem mentioned in Beginer’s Woes about sorted out. I replaced the corroded tension disks with a set I got from eBay. That made thing worse. After searching the web, and asking on a few forums, I finally got pointed in the right direction and was able to locate and fix the problem in about twenty minutes. There were a couple of rough spots on the bobbin case that were holding back the thread as it was pulled around the bobbin just enough to balance the roughness of the tension disks. When I replaced them there was too much funny tension on the bobbin side. That caused the tension to change with speed, so it could not be set properly. It only took a few minutes with a fine stone to smooth the spots out. Nowhere on the web could I find an answer to “tension changes with speed”. There the search engines ought to find that and the next person will not have to scratch their head for a week.
Which brings us to a book review: Hutchison, THE COMPLETE HANDBOOK OF SEWING MACHINE REPAIR, Tab Books, 1980. The information in the first two chanpers you can get out of your sewing machine’s manual. Chapter 4 covers old Plaff SM’s. Chapter 5 covers old White SM’s. Chapeter 6 covers New Home SM’s. Chapter 7 covers one Brother SM. Which leaves chapter 3. Chapter 3 is the useful one. It tells you what needs to be checked and set rights. However it does not go into much detail as it is only 17 pages wrong. These are selling for $30 and up, way up, from used booksellers. Save your money unless you have and old Plaff to fix. As an aside, the writer does not seem to be a sewing machine mechanic, just a writer trying to make a buck; in other words, the book is not authoritive.
Your comments and corrections are always welcome
Scissors
I once worked at a place where I used scissors rather a lot. When I went to work there, they gave me some gloves. Nice people wanting to protect my hands. Not so, what happened is I used those scissors until I developed blisters. Then I used them some more until the blisters broke. And some more until my hands were bleeding. That was what the gloves were for, to keep my blood off the product. So I kind of consider myself something of an expert about scissors. At least enough of one to know that those were not simply scissors, but heavy duty industrial bent trimmers, heavy duty fabric shears in other words. Industrial shears like that would be called tailors shears in a less intense job, and would have had a highly polished chrome rather than nickel and paint finish. Next down the line are industrial bent trimmers. Those are less fancy versions of your dressmaker shears. Then there are the straight trimmers, they are a heavy duty version of what are called sewing scissors.
OK, we have mentioned scissors and shears. There are also snips. What the heck is the difference? Well, it is not exactly what I read on the web. Shears have two characteristics that scissors do not: One, they are asymmetrical, one blade and handle is different than the other. Usually the bottom blade is heavier and may be sharpened at a different angle that the top blade. The top blade usually has a finger ring while the bottom usually has a thumb ring, however that is not always true never mind what the web gurus claim. Two, they are heavier duty than scissors. While scissors typically have two same size finger rings, and symmetrical blades (Unless they are designed for some special purpose, then the blades can be very different). Snips tend to have short, high leverage blades.
Basically scissors (Using the term generically here, confusing, huh?) have one of three different bevels to their edges. The sharpest is the so-called knife edge. The knife edged blades are beveled at approximately a 45 degree angle. Scissor edged (Boy, we are sure getting a lot of use out of that word, aren’t we?) are something like 60 degrees. And finally the last which I never heard a definitive name for is near 90 degrees. You see that one children’s safety scissors, pinking shears, and on some real heavy duty stuff. To understand what that means you have to know how scissors cut.
If you look at a pair of good scissors you will see that they are somewhat bowlegged. Hold them up to the light with the blades closed and look at them edge on. You will see that they make contact at the tip and maybe the hinge, but that there is open space between them just like between the bowlegged guy’s knees. When you open them up you will se that the blades are making contact at the base near the hinges. Then as you slowly close them the contact point moves up the blades towards the tip. Scissors cut by shearing action right there at the contact point, the reason they cut so easily is because all the pressure of the sharp edges is on that tiny point, like just a couple of thread in your fabric, which moves up the blade and thus down the material. Now look closely at the beveled edge of the blade. You will notices that it is ground crosswise leaving tiny crosswise ridges that make the contact point with the material have a micro saw tooth edge. That edge grabs the material and prevents its slipping so the shearing action can work on it. If the edge is too smooth the scissors push the material along ahead of it instead of cutting. The slippier the material the rougher the edge needs to be. Think about that the next time some self appointed expert tells you to sharpen your scissors by running a stone along the length of the blades. There is a way of using scissors with very smooth very sharp edges; that is call slip cutting where you keep the scissor blades in one position and push them along the material. In that case they are not shearing the material they are cutting it like a knife, only from both sides at once.
Scissors dull in two ways. First, the edge folds over, leaving a narrow wire edges just like on a knife. Then that wire edge breaks off leaving the edge rounded. Once the edge is rounded the scissors need to be resharpened. You can delay that by occasionally stropping the edge to remove the wire edge before it breaks off. My favorite strop for scissors, and knifes, is the card board on the back of legal pads. It has just the right texture and hardness to remove a wire edge without damaging the bevel. You do not want to press hard; you are polishing, not honing the blades. Honing, resharpening, can be done by hand, but if you do not know quite a bit about putting new edges on tools you are probably better off having it done by a pro (Yes, I know, not everyone who claims to be one is one; but often you can send the scissors into the distributor for resharpening. I know that Gingher offers that service for $7.50 including return postage as of the time I am writing this).
That brings up brands. In the USA as of now there are three major vendors of forged scissors (If you are not buying forged ones, just toss them and buy new when they get dull it costs about the same): Wiss, they are an old American brand, but sold out to Cooper Tools who has them made, I guess, by the lowest bidder. They are still a decent scissor, but they are not pushing the retail market seemingly preferring to go for the industrial trade. Gingher was a German company. They were bought by Fiskars, and are made in various places around the world just as are Wiss. The ladies love them, probably because they are sold at JoAnn Fabrics. The third is Mundial. Mundial scissors are made in Brazil, but they have been made there for a long time. I understand that they started out as a German company but moved the whole kit and kaboodle to Brazil about 50 years ago. They seem to make the widest range of patterns of the big three. All three make hot drop forged high carbon scissors, that kind holds its edge better than stainless steal does so stay sharp longer. There are some Chinese, and Pakistani made forged stainless steel scissors at pretty nice prices out there, but I am not sure of the quality.
The next tier down are the flat, stamped stainless steel scissors, the top brands seem to be the Japanese Kai, and the American Wolff, Fiskars also makes this type of scissor. They seem to be a good value, but as I said, I would not bother having them resharpened.
There are also some small makers out there that make extremely fine scissors, at extremely dear prices. I do not know much about them, I go into convulsions at the thought of spending $350 for a pair of scissors.
The only other maintenance scissor need is an occasional drop of oil on the pivots, and a wipe with a very lightly oiled cloth. Your sewing machine oil is fine for this. The way I do it is to wipe the excess oil from oiling the pivot off with a soft cloth and then use the cloth to wipe the blades. Usually just the right amount of oil. If it looks oily, wipe again with an oil free area of the cloth. The purpose is to prevent rust, and insure smooth cutting.
Your Comments and Corrections are always welcome.
Beginner’s Woes
I have sewn two simple learning projects: 1. a dust cover for the sewing machine 2. A dust cover for my inkjet photo printer that does not get used a lot as I have a laser for routine printing. Both were made out of an old blue bed sheet.
Sewin machine dust cover
The sewing machine cover was really to test the machine (And I found out that it had a tension problem that I have only done a jury rig fix of until I can get a new tension assembly; which I have ordered). I designed it as a wrap over with sewn-on in ends. It went together fairly easily. I did have problems sewing along the edge of the bottom hem. The needle wanders too much for the adjustable hemming foot which has stitches only about 1/32 of an inch from the fold over, and the zig-zag foot is not accurate enough to maintain a even edge either but I was able to sew farther from the edge (1/8 inch) and do an acceptable job, for a first try.
The inkjet cover I designed as one cruciform piece with just four seams. Made a pattern from craft paper, and when I went to make it today, I found I did not have a big enough piece of sheet left to do it (it started life as a fitted sheet and had a few holes I had to work around). So I changed it to the same style as the sewing machine cover. Only I wanted to try using fusible tape instead of pins.
The fusible tape makes stitching real easy, but is a bit of a pain. You have to have the temperature of the iron just right, very hot, but not too hot. It oozes out and gets on the ironing board cover and the iron (I found that using a sheet of paper under it helped with that problem); it also is not obvious how to make the corner seams between the sides and top of the end pieces and the wrap over piece. I now have a zipper foot so it was not difficult to control the edge stitching on the hem.
What I found out, besides making sure you have a big enough piece of fabric (grin), is that you do not need an inch of ease on a dust cover, one-half inch, or maybe even none, would have been enough. The sides do not need to be as tall as the top of the object to be covered because of droop. So both covers are bigger than they needed to be, but I guess that is better than too small. That you should check your seams for tension every so often, I had a couple that were loose on the top tension for some reason while all the rest were fine (I have since figured out that the cause of that was not enough pressure on the foot). That one needs to work carefully and not get impatient; I have a problem with that especially when things don’t go the way I planned. That running upstairs to use the iron, and back down to use the sewing machine is a pain. That I really need a tee-square and a couple of curves for laying out patterns.
I think my next project will be something with curved seams; and my next article will be about scissors as I find that there is a lot of no-sense about them on the web.
Your Comments and Corrections are always welcome.
Singer 337 Sewing Machine Review
The Singer 337 appears to have been manufactured in Scotland for the 1964 and 1965 model years. The writer has seen two versions of it. One, like the one reviewed here, without a needle position selector, and one with the needle position selector. He does not know if they were two different models or just ’64 model and ’65 model differences. He has also seen two color variations, light blue like this one, and light green. The both seem to have the same greenish plastic top cover.
The 337 is a basic Zig-Zag machine, with a drop in plastic bobbin. The top arm cover is plastic, the name plate is plastic, the tension dial, but not the mechanism, is plastic. Every thing else is metal. All gears are steel. The machine is technically a horizontal rotary oscillating hook type which tends to be very reliable. The lack of frills also lends itself to reliability. Since it has dual tension slots and an oscillating hook, it should only be a matter of adding a second spool pin to use twin needles with it.
Slide Show of Singer 337 Images
There was a slightly more expensive companion model, the 338, that had interchangeable cams and thus a wider selection of stitch types. As far as the writer can determine the 337/338’s are very similar to the proceeding 327/328 which had an external motor, and the subsequent 347/348 which had a belt driven rotary hook. He was unable to find a Service Manual for the 337/338 but has one for the 347/348 and the only difference he can see is that the 337/338 has a walking bar driven oscillating hook, while the 347/348 has a cogged belt driven rotating hook, and a couple of nylon gears.
There are two main levers on the front. The vertical one controls the stitch length and forward/reverse. The stitch length can be varied from 7 per inch to 30 per inch; plus there is a setting for 6 stitches per inch basting, but it is locked and the lever can not be moved to reverse at that setting. Just below that lever is a switch for the light. And just above it is the Bobbin Winder control. The horizontal lever controls the Zig-Zag with from Zero, straight stitching, to 5, about a ¼ inch wide. On the model with the Needle Position selector that is just to the right of the Zig-Zag selector. There is, of course a knob to adjust Thread Tension. A foot controller for Motor Speed is the only other control on the machine.
It uses a standard 15×1 needle, plastic bobbins, a 15 watt bayonet light bulb, and sewing machine oil all of which were available at the local Wal-Mart. You also need a small tube of sewing machine grease for two gears in the top that the local Wal-Mart did not have.
The 337 uses Low-Shank feet like most Singer Machines, except the Slant-Needle ones, since 1851 and many other makes; so sewing feet are easy to find. Look for “Low-Shank, Featherweight, Singer, etc. The reviewed machine came only with a Zig-Zag Foot. The writer has acquired a couple more from eBay and has found no problems with them.
Bobbins are wound with the thread spool in the sewing position. The thread is run to the front clip above the Thread Tension Control, and back down to the bobbin tension button near the base of the pedestal then up to the bobbin. The bobbin winding selector is pushed to the back of the machine and hit the foot control. It only takes about a minute to fill a bobbin.
As mentioned the bobbin is a drop in one. Just open the bobbin cover by sliding it towards you and drop the bobbin into the bobbin case. Slide the thread under the tension spring and into the slot on top of the bobbin case. Then close the bobbin cover with the loose end hanging out. Hold the needle thread and cycle the machine with the hand wheel with will pull up a loop of bobbin thread. Catch that loop and pull the loose end through. Nothing fiddly about it at all.
Can not say the same about the upper threading. However every old vertical needle Singer the writer has ever used is threaded exactly the same way. From the spool to the thread guide, down around between the tension disks, lift the tension spring with the thread and loop over the hook, then run it through the hole in the lever, down to a guide on the front plate, and then one on the needle bar and through the needle eye front to back, flip it under the foot and towards the back of the machine. Done.
So, how does it sew? About like an old Singer Sewing Machine. In other words, if there are no problems with the machine, there are no problems with the sewing. If there are problems with the machine there is a lot of help out there for the asking.
The only potential problem the writer can see with the machine is that it apparently was only made for two years. That means that any parts that are unique to it may be hard to find replacements for. On the good side of that is that most of the parts are commen with other model singer sewing machines, so he has no problem recommeding the 337 to anyone looking for a basic reliable zig-zag sewing machine.
Your Comments and Corrections are always welcome.
Thread, Fabric, Needles, and Tension
Well, I have spent a bit of time getting things in order. First, I am, most likely, going to have to take the upper tension adjuster apart and clean it thoroughly. Why? Because sometimes the thread runs through it perfectly, and sometimes it gets real tight. Which I think indicates that something is jamming it off and on. But, I will wait until the service manual I ordered gets here.
Ah hah! A little oil; who would do that? Do Not Oil The Thread Tension Assembly! OK, now that I have gotten that off my chest, there was also some rust and a clump of oily lint in there. It does work better now. By the way, I found a parts break down for the Thread Tension Assembly in a Singer 301 Manual I found online. Apparently folks were smarter in 1950, because they do not think we can do something like that today.
What I have relearned about tension adjustment is that almost no one agrees with anyone else about how to go about it. That being the case, I will just go through the process that worked for me. (Note, if your machine is working perfectly, do not mess with it.)
First match your needle to your thread, the medium weight dual purpose poly I mention a bit further along works well with a 14/90 needle. Some finer Mercerized cotton/polyester thread I have wants an 11/70 needle, and the button thread I use for heavy sewing wants something like an 18 /110 needle. If the needle is too big for the thread, the thread flops about and it is hard to get an even stitch. If the needle is too small the thread drags and eventually breaks. This is all by feel nowadays, it used to be that they told you what size the thread was and you had an easy starting point (My age is showing, huh?).
Now that you have the right needle and thread, let’s see if we can not get those pesky tensions where they are supposed to be.
First, the Bobbin (Bottom) tension is your course adjustment. You should only need to mess with it if you can not get things right with the Thread (Upper) adjuster. Tension seems to be something of a misnomer, drag would seem more correct. What you are trying to do is bring the drag on the top thread into balance with the drag on the bottom thread. BTW, it seems like the hardest thing to get into adjustment is fine slick thread, in light weight fabric, with long stitches.
Setting bottom tension
- Set upper tension to the middle of the dial.
- Load the machine; spool and bobbin, with medium weight thread (Coats and Clark Dual Duty Polyester say).
- Run a seam across a couple of layers of medium weight fabric.
- Inspect the stitches.
- If the upper thread is tight (loops on top) tighten the bobbin tension screw ¼ turn.
- If the lower thread is tight (loops on underside of the fabric) loosen the bobbing tension screw ¼ turn.
- Go back to 3 and do that again until there are no loops (Note: ¼ is a lot of adjustment. And if the loops move from one side to the other this time turn the screw 1/8th turn back.
- When there are no loops on either side the bobbin tension is about right.
Setting top tension
- Run another stitch.
- Inspect it.
- If both threads go into the fabric about equally it is set correctly
- If the top thread goes in deeper, tighten the upper tension 1/2th number.
- If the bottom thread goes deeper loosen the upper tension 1/2th number.
- Note: once again this is a big adjustment; it is enough go from one thread size to another.
- If not satisfactory, go through this procedure again; only just turn the tension 1/4th number.
The idea is to go past the correct setting then adjust back ½ of what you did before. By successively halving the adjustment you get closer and closer to the correct one until you get to a point where is not worth bothering to try and get it closer.
Now run some long seams at full speed. You may find out that you need to tighten the upper tension just a bit to keep it from throwing loops. Do not confuse these loops with the ones you get from the wrong bottom tension, like I did at first. It only takes a little bit more upper tension to control these, like an 1/8th of a number. Ever see anyone else mention this? I haven’t.
You will have to redo the top tension when you change thread, needle, or fabric, but it will only be a little bit.
A final suggestion, make a note of the settings for that thread and needle. That give you a starting point next time you use it; and if it changes much you know something is wrong. You will most likely have to diddle the setting a tiny bit depending upon changes of fabric and humidity.
ADDED: I have found that the Dual Duty thread works fine with the #11 needle in finer fabric.
Your Comments and Corrections are always welcome.
Types of Sewing Machines
There is a lot of misinformed information, self-serving statements, and outright lies about different types of sewing machines out there. I thought I would write a short article to try and alleviate the confusion. First I have to admit that there are no hard and fast definitions, much less legal ones. Second I am talking about mechanical sewing machines, computerized stepping motor controlled machines are outside of my knowledge base. With that in mind here we go.
- Light Duty. Occasional use. Mending, hemming etc.
- Home. Intermittent use. Making garments, draperies, etc.
- Commercial. Continuous use. Otherwise the same use as home machines.
- Industrial. Continuous use. Very high speed. Production equipment.
- Leather. Sewing heavy leather.
You can get by using a machine one step above its design type, if you realize it is going to be slower and not last as long. Lower end commercial sewing machines are really just high end home machines with bigger motors, their real advantage is their versatility. Which kind of points up the probably obvious fact that you can do the smaller jobs on the heaver machine as well at least with the general purpose light duty, home, and commercial types.
Light duty machines like the Singer Featherweight and most of the plastic sewing machines you can buy at the discount department stores are fine for getting your feet wet. Just realize that if you get into doing more than they are meant for you are going to want to replace it. Light duty machines usually have low-shank presser feet (I will explain about presser feet in a later article, but I wanted to mention it as it is one indicator of the grade of sewing machine). By the way, the Singer Featherweight sewing machine is something of a cult collects item often selling for ridiculous prices considering that their main claim to fame was that they were the cheapest real sewing machine you could buy. They are cute as a bug, however.
Used older home sewing machines abound on eBay. The sellers often tout them as “Near Industrial Sewing Machines”, and like to show photos of it sewing 6 layers of leather. They do not mention sewing more than that little patch they show would burn out the motor. My own Singer 337 fits the lower end of this class; the upper end is something like a 401A Slant Needle machine. You can get new machines of this class at the local sewing store. They usually have metal drive components and either low or slant shank presser feet. Using these as commercial machines is going to mean replacing the motors often.
Commercial Machines are harder to find. You can not even tell by what it says on the box as “Commercial Grade” is an advertising term, not a type designation. A high end home machine can be used as a light duty commercial machine. In fact an older outside motor home machine can often be converted to a commercial machine by just upgrading the motor. If you are planning on running your sewing machine 8-12 hours a day a commercial sewing machine is what you are looking for. If you are only going to use it an hour or two at a time you can get by with a home machine. Real heavy duty commercial sewing machines, like industrial sewing machines, usually have high shank presser feet. Even dealers sometimes call these industrial machines, they are not. One telling point is that if it seems like a rather plain sewing machine and costs $500 to $1000 new it is probably a commercial.
Industrial machines can be bought from Industrial Sewing Supply Companies. However they are not real useful for home use because they do not have the features that we have come to regard as essential for general sewing. Also they take quite a bit of experience to control because they are so fast and powerful. Despite well meaning advice you do not want one of these. If you are only going to buy one sewing machine, trust me on this. Almost all industrial machines have high shank knee activated presser feet.
Leather Sewing Machines are specialized machinery. They are very big and heavy and powerful, and usually mounted on a cast iron floor stand. You are not likely to mistake these for something else.
So, you are likely wanting one of the first three types. I would suggest a good used home machine unless you have a reason for wanting a commercial machine, or are sure you will never do more than light sewing. I also recommend a basic zig-zag machine. The fancy ones do all kinds of fancy stitching and embroidery, that most of us guys will have no use for, while making the machine more complicated and expensive. Although, I admit, the main reason I recommend a basic zig-zag home machine is that used ones are cheap. I paid $15 for mine at the local Goodwill Store, and you can usually get a pretty good one for under $100 on eBay.
Your Comments and Corrections are always welcome.