How To Select The Proper Thread For A Material (Leather)

[Evo160K]

While researching how to restore a Claes sewing machine, I came across a number of general comments on thread selection. The most frequent comment was, the thread selection is determined by the material being sewn and the needle size is then determined by the thread and size selected. Being new to sewing, sewing machines and this fine website, may I please ask:

what specifically are the major factors to consider when selecting a machine thread for any material and for leather material in particular? I'd like to understand the reasoning that goes in to the choice

Thank you, thank you very much.

[johnv474]

Ideally, thread will fill the hole created by the awl/needle, for structural reasons and for weather resistance. Thickness of the thread is affected by hole size, strength desired, aesthetics (people consider a higher stitch per inch to look 'finer', proportion to size of the good, etc.). Needle size is affected by the needle's strength, thread used (to fit in the eye). Thread choice is affected by desired properties: cotton is cheap but weak, linen is traditional and has some 'flex', nylon is synthetic and often stronger than linen but susceptible to UV damage over time, polyester is expensive, strong, and UV resistant. Synthetics are hard on the fingers if handsewing and stretch over time. Some customers prefer traditional threads if they do reenactment, etc. There is a debate about whether you want thread too strong--you may prefer a seam to break than for leather to tear.

[Evo160K]

Johnv474,

That helps, makes good sense. Thank you. Are you able to suggest a source where I can learn more about the relationship between the fabric characteristics and the thread choice?

" There is a debate about whether you want thread too strong--you may prefer a seam to break than for leather to tear."

This comment tangentially reminds me of a requirement we had to meet for boots worn around molten metal. The sole thread and other thread had to hold up for a number of seconds in case of an accidental immersion, but the laces had to burn through instantly to let the wearer "kick off" the hot boot. Thanks again.

[charter]

Hi there. I don't know anything about the Claes machine but Google says it's a patcher. That machine is so different than mine I am not qualified to comment on it specifically, but there are many who can on the site.

But your post pushed a button for me. At this point I've made ALL the possible mistakes related to needles and thread, so here are a few thoughts and a post I wish someone else had made when I first started out.

Two kinds of thread are important to know for leather. Bonded nylon is probably the most common and cheapest. Polyester is used for outdoor applications to minimize UV damage. They both work fine on most things so don't overthink it. But you can also get fire resistant, Kevlar, cotton, monofilament, and lots of others for special uses if you like a little complexity.

For thread size, the heavier the leather and the more you want it to show, the thicker you should go. #69 is the minimum for a lot of leather sewing machines. It's strong as heck and barely shows. Thicker than that is so strong it no longer matters IMHO unless you're making something where weight-bearing safety is the primary concern (e.g. a fall protection harness). If the stitching is not a feature, i.e. used mostly for fastening, #69 or #92 works fine for 1/16" up to 3/8" thickness, the max for my machine. #92 is my default choice and is in my machine most of the time. Some like different sizes in the bobbin but I always match them. I use #207 for stitches I want to show.

Bob from Toledo has posted a helpful chart indexed by thread size here: http://www.tolindsewmach.com/thread-chart.html

Another more detailed chart, indexed by needle size, is here: http://raphaelsewing.com/blog/?p=11

Though I'm sure it happens, I've never seen good quality stitching or material tear except when either is very thin.

It's usually best to have a strong connection between layers when you sew - use spring clips, or, better, use tape or glue before sewing.

The most important thing for good stitches is to adjust the upper thread tension to the thickness of your material. To do this, use similar scrap leather and, starting loose, do sample stitches until the upper thread is no longer visible from the bottom. Tension adjustment will quickly become second nature but it's laborious at first. Also, plenty of more obscure things can go wrong. Here are a few: http://aces.nmsu.edu/pubs/_c/C-202.pdf

Another very nice page from the same site about using/maintaining machines: http://aces.nmsu.edu/pubs/_c/C102/welcome.html

Finally, in addition to the sewing machine vendors on the site, Wizcrafts, Art, and other members seem to know literally everything about sewing machines and I am grateful for their expert posts in getting to the intermediate skill level. And you're right, this is a great site. So thanks to the ops team as well.

[johnv474]

For what it's worth, the most common thread we sell to shoe repairmen is the #92. We have a Claes patching machine in the back (the first, and only, leather sewing machine I've used). I think it has #69 thread in it, and stitches at about 6 spi. That is fine for small accessories, like possibles bags. It is using nylon thread at the moment.

[Evo160K]

Charter,

That's exceptional information! Thanks so much. I know you spent a great deal of time putting that reply together and I appreciate it. Thank you. I'll need to read it several more times to really absorb it. Hopefully you've helped me avoid some of the mistakes beginners make. By the way, what is a "spring clip"? Thanks again, Charter.

johnv474,

What model Claes do you have? I've run into a small puzzle trying to get the correct replacement spring for a broken one in the needle bar assembly. My model is an 8345 and there are three springs in it...........that's if they're all original.......the machine is 40 years old. The replacement spring that came in is 9 mm in diameter and is much larger in diameter than the three in the machine. Since I don't have the 8345 parts list I have no idea if it's correct or how many should be in there. The 8346 parts list shows only two springs, if I'm translating the German correctly, and one is 9 mm in diameter. Do you know anything about the 8345? Thanks very much.

Edited June 3, 2014 by Evo160K

[charter]

Spring clip = one of those little clamps that are used for paper in offices - they work perfectly for keeping the leather layers aligned. Just make sure you unclip them before the machine crunches them into a useless shape. And many thanks for he kind words!

[Dwight]

Actually, in today's leather goods market, . . . the propriety I place on the stitching, . . . is the look one wants to achieve. In years past, . . . not having some of the strong materials we have today, . . . size and strength sort of went hand in hand.

Today, . . . some very small threads are as strong as yesteryear's large threads.

I generally use 346 thread on all my holsters and belts, . . . even on one particular billfold application, . . . because of the "look" it gives. I tried 207 and 277 but was unhappy with the visual results, . . . although I am sure the physical strength was quite adequate.

I even use some 415 occasionally, . . . as it is a bold look that adds to the "macho" flavor of some of the things I do.

But again, . . . I really believe in today's market, . . . one could use most any size (relatively speaking) and if the pieces were properly bonded beforehand, . . . there should be no real fear in using whichever size looks the best.

May God bless,

Dwight

[Evo160K]

Pastor Dwight,

Thank you for the good wishes. I appreciate it.

Thank you also for the thread information. It's reassuring to learn thread strength is not as much of a consideration with today's quality threads as is the look of the thread. That might have taken me a while to learn on my own.

Charter,

Thanks for the spring clip explanation. I'll get some.