Mechanics of Serged Seams

[tweeds]

when sewing the inseam is the overlocking and double chain stitching made in one single operation by one serger? (5-thread serger?) or is the OL and CS made in two separate parts by the same machine or on two different machines alltogheter?

repeated Begs' question in a more specialised setting...

ande, tg or anyone else?

[Bijan]

I have a pair of 70's 501's where the CS veers way off from the serge, so I'm gonna go with 2 machines. Here they are, early 70's redlines. Looks like someone had a four beer lunch...

It's actually not too noticable from the outside. I wondered about this myself a while back. These jeans kinda cleared it up for me.

[ilovespaz]

its two machines from my experience, this seam is much quicker then the felled seam which is one machine. first they would lay down a row of stitch to join the seams, fold it over, lay down another line so the seam would stay in one place and to also have a top stitch color on the inseams, and then use the serger last -- this seam also prevents leg twist --

[andewhall]

Yeah two machines like ilovespaz said. Plain stitch or chain stitch the inseam together, overlock it, top stitch it. I would say a felled inseam would be much quicker, one machine, one action.

[tweeds]

this seam also prevents leg twist --

ilovespaz, could you elaborate?

ande, i'd thought the felled seam required two actions on one machine...? two lines of stitching that is.

[Bijan]

Leg twist has to do with the threads that the denim is woven from trying to straighten out. Not sure if it's the weft or not. At least that's my understanding.

[XX]

flat felled seams - like levis seat seams, wrangler side seams, etc are done either on a double needle machine with a special folding attachment, or theyre done on a machine like a Union Special 35800 or similar

its a one step operation unless its a "hand set" felled seam like you see on some japanese jeans and levi 1890s/1900s repros. if it is hand set then it is a 2 or 3 step operation

Whenever the inseam is sewn (without having top stitching or being pressed open) its usually done by an overlock in one step as well.. It is called a 5 thread safety stitch machine like this stitch http://www.chholderby.com/images/IndSew/sergers/516-5.gif

i would imagine that older 40s/50s levis would be the same.. a one step operation as well since these machines have been around for a while. the picture Bijan posted looks like those jeans might have been altered or tailored for a better fit before he/she got ahold of them? i could be wrong..

ive seen some pairs of levis on ebay from the early 1900s where the whole pair appears to be single stitched with no overlocking at all. it seems like the topstitching was more of a way to prevent the seams from unraveling completely..but thats for a whole other thread!

[ilovespaz]

Leg twist has to do with the threads that the denim is woven from trying to straighten out. Not sure if it's the weft or not. At least that's my understanding.

this also does leg twist, but when you flat felling, the prevention of leg twist happens when a poor operator applies uneven pressure to either the top of the fabric or below the fabric into the folder - - you can see it when you cuff your jeans up and look at the hem, the inseam flat felled tends to not line up on top of each other - a good operator will apply even pressure to the folder and the machine to get the fabrics lined up correctly. from my experience in production, even though it takes two machines to do a non flat felled, it's more consistent seam since most operators can sew in a straight line - - you can see my paint diagram below to see how a flat felled machine sorta works - - well yeah.. sorta ---

[40ozprophet]

this also does leg twist, but when you flat felling, the prevention of leg twist happens when a poor operator applies uneven pressure to either the top of the fabric or below the fabric into the folder - - you can see it when you cuff your jeans up and look at the hem, the inseam flat felled tends to not line up on top of each other - a good operator will apply even pressure to the folder and the machine to get the fabrics lined up correctly. from my experience in production, even though it takes two machines to do a non flat felled, it's more consistent seam since most operators can sew in a straight line - - you can see my paint diagram below to see how a flat felled machine sorta works - - well yeah.. sorta ---

Its all so clear now?

[ilovespaz]

i tried my best, oh well - - when you apply un even pressure to either the top or the bottom, the fabric will roll onto itself, which makes the seam sew crooked - -

[Bijan]

spaz- if you are referring to the hem stitch, I believe that twist is a by-product of a Union Special or similar chain stitcher.

[40ozprophet]

i tried my best, oh well - - when you apply un even pressure to either the top or the bottom, the fabric will roll onto itself, which makes the seam sew crooked - -

Now i gotcha. thanks

[XX]

yes - leg twist can be caused by sewing, but if that were the case, you would notice it even on a rigid jean

[tweeds]

actually, i thought that leg twist was a feature of unsanforised denim. i'm guessing ilovespaz is referring to a leg twist that happens due to a badly done seam, in which case XX's point stands - you would see it on a raw jean, even before the wash (after which the twist is noticeable). i was kind of wondering how an overlocked seam could prevent something which was inherent to the denim.

and with regards to begs' original question, there seems to be some sort of contradiction here. or is it safe to assume that the industry approaches the seam in two ways, one breaking it into two steps and the other combining it all?

[swisloc]

actually, i thought that leg twist was a feature of unsanforised denim. i'm guessing ilovespaz is referring to a leg twist that happens due to a badly done seam, in which case XX's point stands - you would see it on a raw jean, even before the wash (after which the twist is noticeable). i was kind of wondering how an overlocked seam could prevent something which was inherent to the denim.

and with regards to begs' original question, there seems to be some sort of contradiction here. or is it safe to assume that the industry approaches the seam in two ways, one breaking it into two steps and the other combining it all?

2 steps for an overlocked inseam, 1 for a felled inseam... seems like that's the concensus here, or is my head spinning in circles. this is correct to my knowledge, but as ilovespaz said, despite being 1 step, the felled seam is more dificult to do straight.

now, not to derail the thread, but, as far as leg twist, let me throw this out there (into the repro-loving masses). leg twist is a product of an unwashed woven product that shrinks and is pulled in the direction of the weave upon shrinking creating twist (as we all know). However, sanfordizing the denim along with modern pattern making can substantially reduce leg twist (as i'm sure everyone has noticed on their APC or Nudies). So i bought a pair of Denime 66's One Wash for my textile designer girlfriend, and the first thing she says is, "they cut the pattern wrong, the leg is twisted, take it back." i explained to her the repro companies desire to replicate the leg twist of old unsanfordized denim. her response: "any compitent modern clothing company should be able to calculate the twist pre-wash so it ended up straight."

which leads me to this: why are we in love with leg twist? this is not a rhetorical question; i am interested, why do we all like the leg twist?

[synthi]

I think I recall posts by Ringring where he has suggested that leg twist is a result of the fabric following the direction of the weave at the point of shrinking. This reinforces what you're saying swisloc.

As to why leg twist is desirable, to me it's part of the inherent quirky, 'flawed' and the two fingers up to formality that's at the very heart of denim. More specifically, because much like the selvedge seam itself, it's a throwback to vintage denim.

[swisloc]

I think I recall posts by Ringring where he has suggested that leg twist is a result of the fabric following the direction of the weave at the point of shrinking. This reinforces what you're saying swisloc.

As to why leg twist is desirable, to me it's part of the inherent quirky, 'flawed' and the two fingers up to formality that's at the very heart of denim. More specifically, because much like the selvedge seam itself, it's a throwback to vintage denim.

i know full-well shy it occurs, and i can understand the interest as a homage to vintage denim, but my question is that if people desire certain modern construction details/ patterns such as narrow profiles, low rise, poly blend threads that won't break, etc...then why not straight inseams? It makes me wonder (at times) why some of the repro brands would even retain the leg twist, when they have broken with "tradition" in so many other areas. a company like Sugarcane, which, in part, is trying to make very accurate repros i understand, but why some of the other brands?

i'm valueing or de-valueing the leg twist, just posing the question.

[Begåvningsreserven]

Yeah two machines like ilovespaz said. Plain stitch or chain stitch the inseam together, overlock it, top stitch it.

so easy, i feel stupid now. I dont know why i just assumed that the overlock would come first, that is what confused me. Thank you kiwiboy

[Thorns]

hmmm... I'm sure my way is screwy, but i do it in like a four step process. First I stitch it together, then I overlock, then i turn the denim over and do both lines of top stitching. Am I retarded?

[synthi]

i know full-well shy it occurs, and i can understand the interest as a homage to vintage denim, but my question is that if people desire certain modern construction details/ patterns such as narrow profiles, low rise, poly blend threads that won't break, etc...then why not straight inseams? It makes me wonder (at times) why some of the repro brands would even retain the leg twist, when they have broken with "tradition" in so many other areas. a company like Sugarcane, which, in part, is trying to make very accurate repros i understand, but why some of the other brands?

i'm valueing or de-valueing the leg twist, just posing the question.

Swisloc you've elaborated upon your original question but in doing so have steered it into a different direction. From what I understand, back in the 40's and 50's, the phenomenon of leg twist was seen as an undesirable side effect of washing jeans and Lee & Wrangler, with their sanforized shrunk denim, played on this as a sales tool. Modern jeans manufacturers could do the same. Maybe some of them like Nudie & Somet do, they just don't shout about it probably because it's not that a big a deal.

One of the most beautiful expressions that for me succintly sums up Japanese philosophy is 'imperfection is perfection'. That kind of thought probably stems from the Samurai and / or Shinto Buddhism. I love that expression. For me it eloquently answers why so many of the Japanese repro labels seem happy to transcend while still embracing the 'flaws'.

[andewhall]

so easy, i feel stupid now. I dont know why i just assumed that the overlock would come first, that is what confused me. Thank you kiwiboy

Haha, no problem Dear Leader:D

[swisloc]

Swisloc you've elaborated upon your original question but in doing so have steered it into a different direction. From what I understand, back in the 40's and 50's, the phenomenon of leg twist was seen as an undesirable side effect of washing jeans and Lee & Wrangler, with their sanforized shrunk denim, played on this as a sales tool. Modern jeans manufacturers could do the same. Maybe some of them like Nudie & Somet do, they just don't shout about it probably because it's not that a big a deal.

One of the most beautiful expressions that for me succintly sums up Japanese philosophy is 'imperfection is perfection'. That kind of thought probably stems from the Samurai and / or Shinto Buddhism. I love that expression. For me it eloquently answers why so many of the Japanese repro labels seem happy to transcend while still embracing the 'flaws'.

yeah, that's my understanding, too, and the reason that most companies producing woven fabric clothing take it into account in pattern making and pre-shrinking (or in the case of raw fabric, sanfordizing). and i think i'm pretty clear as to why you like leg twist. but it just struck me funny, that someone in the textile trade would say that it was a sign of inferior pattern making. i can understand someone wanting twist for an aesthetic reason, but i guess i don't see how it's grouped as one of the many "imperfections of denim clothing" when it's actually a design/contsruction imperfection that can be easily remedied. that is to say, it's not a denim "flaw", it's a manufacturing flaw.

perhaps that's similar enough, but it makes me reconsider leg twist. i mean, why wouldn't a company (lee, wrangler of old) play up the fact that their seems didn't twist? It was fixing a flaw, not a sales pitch.

[tweeds]

well i guess as far as progressive design is concerned, selvedge denim should have no place in the world, seeing as how it offers a more unproductive use of denim (narrower width, fewer patterns cut from a bolt) with no significant advantages over non-selvedge denim.

but perhaps synthi is oversentimentalising the leg twist? i'd say it's just "one of those things" that has been kept in place, just like aforementioned selvedge. i wouldn't argue with swisloc's contention that it's an imperfection that can be easily remedied, but that doesn't mean it should...

[swisloc]

well i guess as far as progressive design is concerned, selvedge denim should have no place in the world, seeing as how it offers a more unproductive use of denim (narrower width, fewer patterns cut from a bolt) with no significant advantages over non-selvedge denim.

but perhaps synthi is oversentimentalising the leg twist? i'd say it's just "one of those things" that has been kept in place, just like aforementioned selvedge. i wouldn't argue with swisloc's contention that it's an imperfection that can be easily remedied, but that doesn't mean it should...

oh, i'm not saying it should be eliminated, especially if people like it. i'm just thinking maybe that i don't like it. the only thing that i'd say about the comparison to selvage is that selvage indicates a processual difference [than jet-loomed], while leg twist only indicates that shrinking was not taken into account...

...isn't it great to have informative, interesting denim threads now and then?

[dino might]

...isn't it great to have informative, interesting denim threads now and then?

it really is great.

ive never taken too much of a liking to leg twist myself, i actually find it quite bothersome, and like my denims in spite of their leg twists. im a bit obsessive compulssive at times, and it definately shows when im constantly pulling my legs back this way or that, in vain, as i already know the seams arent going to straighten

i just have to suck it up and try my best to ignore the twist really, otherwise it bugs me

[tweeds]

...isn't it great to have informative, interesting denim threads now and then?

if i had my way, i would chain all the informative, interesting denim thread contributors to the forum

it always is a refreshing change to learn something new about denim apart from how this brand fits and what the sizing is like on that model...

since we're on the subject of leg twist... in right-handed twill like vintage Levi's the leg twists rightward, so would it follow (has anyone had firsthand observation) that in left-hand Lee denim the twist is leftward? and hence logically speaking we can deduce that broken twill would eliminate the twist--which is, of course, the case with Wrangler.

[andewhall]

hmmm... I'm sure my way is screwy, but i do it in like a four step process. First I stitch it together, then I overlock, then i turn the denim over and do both lines of top stitching. Am I retarded?

Na Thorns, you are doing it exactly right man. When are the new joints coming?

Better explained, sort of.

Machine Felled Inseam: 1 machine

Twin needle chainstitch machine set up with felling feed attachment. Thread colour gold or one threaded with gold the other indigo.

One operation.

Overlocked Inseam: 3 machines

1: Inseams stitched together, right sides together. Single needle chainstitch or plain sewer. One operation. Thread in indigo (sometimes light grey)

2: Overlocked on serger machine inside inseam. One operation. Thread colour gold, light grey or indigo

3: Flipped to the right side, Top stitched using twin needle plain sewer. One operation. Thread in gold or one thread with gold one with indigo. (if no twin needle you are sewing two rows here)

I have seen a few factories in full swing, not so much doing jeans but other stuff. Some very smart, big and clean, some small dark and dodgy looking with electrical cords and shit everywhere. Factories are set up like a production line, different stations and machines set up for the various jobs, depending on what they are making. Some factories will specialize in only wovens and others will only do knits…some do both.

So if its jeans being produced there will be machines set up for inseams, waistbands etc. There may be one or many stations, don’t know, guess it depends on the size of the factory. So one operator/worker will be doing inseams all day, and depending on the size of the order, possibly inseams all day everyday for weeks. A teacher I had at Tech worked at a large’ish factory and said she was once on zip flys for weeks, and they could do one in….oh can’t remember, something like 3-4 minutes at a guess, then passed on to inseams etc.

I am thinking that the different thread tones on jeans came about years ago as a result of having slightly different coloured threads on the different machines kind of like the thread was made all the same colour but they were sort of rough and the colours came out different and no one gave a shit because it was just workwear? That’s just a wild stab in the dark however and going off into a dreamland tangent.

[salaami]

which leads me to this: why are we in love with leg twist? this is not a rhetorical question; i am interested, why do we all like the leg twist?

we love it because its how it should be. being a textile designer doesnt make you a denim lover. the first word dudes girl used was "modern". enough said. to me, sanforized denim isnt really raw, since they already took some of the fun out of it.