I.D. and O.D.

Posted by Kathleen Fasanella on Jun 11, 2008 at 12:20 pm / Patterns, Process Reviews, Quality, Sewing / Trackback

This is a continuation of To pin or not to pin so you should read that first if you haven’t already. I.D. and O.D. refers to Inner Diameter and Outer Diameter. This is a common concept in every field of engineering of which sewing is one. However, it’s only in sewing that people assume that two lengths that will be joined must be identical in length. In any other field, one would be laughed out of the room for believing this. I.D is necessarily smaller than O.D., one tucks inside the other. That’s just one reason that sleeves -for example- should not be larger than the armhole to which they are sewn. Sleeves are I.D. tubes sewn into a still larger armhole tube (O.D.).

Using exactly the same pieces from the previous entry, I sewed two tubes as one would in the course of attaching cuffs or inserting sleeves. Below you can see the result of using the improperly cut lengths inserted inside each other.


As you can see, were this a sleeve, you’ve introduced a major problem were there had been none if the goods had been cut correctly. In fact, the point of O.D. and I.D. is that dependent on the weight of goods, one may need to cut the I.D. piece shorter in length than the piece it sews to anyway. Below is a photo showing the seam allowances of each piece are uniform.

In heavier weight goods, these differences are exacerbated. Most of my experience is in leather. I can promise you that using sleeve cap ease in a leather sleeve, polar fleece or in wools, is going to create all kinds of havoc. If one is accountable to 200 line stitchers who have to sew those in and your job is on the line, you’re in no position to argue regardless of myriad sewing naysayers on the web (who arguably might feel differently if they had to set 500 of the same wrong sleeve in a day). I’m not the only one who says this; most people don’t know any experienced professional pattern makers or have occasion to ask them questions. A friend with over 30 years in the business says that as a matter of course, she uses negative ease in all her sleeve caps. She thinks it’s silly that people even debate the matter.

11 Responses to “I.D. and O.D.”

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Todd
June 11th, 2008
1:51 PM

What if, after I sew in the sleeve, I press the seam allowance outward in the sleeve cap area. I do this for most men’s tailored coats for aesthetic reasons. Then the sleeve would be O.D. and the armhole would be I.D., no?

Kathleen
June 11th, 2008
1:57 PM

I press the seam allowance outward in the sleeve cap area.
I do this too but for another reason, pressing allowances fills out that seam area so the seam line doesn’t buckle. However, pressing strategy doesn’t make the sleeve OD. If the sleeve were OD, you’d be putting the body of the jacket inside the sleeve tube to attach it.

Sarah
June 11th, 2008
9:12 PM

I know this may sound dumb, but as a homemaker that just makes garments for herself and family, I have always pinned. I never knew better until I read your posts. Finally you have explained the discrepancies in lengths of some of my garments.

So what do you do instead if you are using a typical tissue paper pattern? Do you pin before you sew a seam?

Leslie
June 12th, 2008
8:09 AM

This problem of discrepancy exists in many of the home-Sewing patterns I have used. Add to that the “pinning” that all of us 4-Hers learned and you have a classic home-made look. Yuck! In high-school I had a home-economics teacher that taught how to set a sleeve without pins. How lucky I was. She was probably born in the early 20s, and judging from some of my vintage books on dressmaking, she probably grew up designing her own garments and drafting patterns. It is really too bad we have lost all that knowledge.

dosfashionistas
June 12th, 2008
10:12 AM

I have been wanting to weigh in on the sleeve issue for some time. I can see the necessity of no ease when working in leather or other thick, hard fabrics. But in lighter fabrics, I have always thought ease was necessary in order for the sleeve to move properly. How else do you allow for movement over the top of the bicep and have the armseye seam hit at the shoulder bone? You are fitting from a larger volume into one that is smaller in a short space.

And your use of the two tubes to illustrate sleeve setting problems is an apples to oranges comparison. Easing the sleeve head is possible because that area of the sleeve is cut on the bias and very mallable. Indeed, most of the sample makers I worked with handled sleeve easy simply by putting the sleeve underneath, next to the feed dogs of the maching and letting the natural machine action do the easing.

I am going go away and think about this some more now…You know what they say about old dogs. And I have to think about pins too.

Sarah@dosfashionistas

Penny
June 12th, 2008
10:31 AM

For me it depends on the fabric and the length of the seam as to if I pin or not. Some fabrics that are extremely slippery are almost impossible to sew if you don’t pin. Placing a pin parallel to the seam is incorrect because this allows the fabric to shift. You always want to pin “across” the seam so that it holds the fabric in place and then remove the pin just before sewing over it to avoid breaking a needle.
I’ll place a pin at the shoulder notch and matching notch on a sleeve cap, because the shape is harder to sew without one. I don’t use many pins tho because it’s usually faster to match notches by hand and sew. Most of my uneven seam lengths are due to certain types of fabric where the feed dogs will move the bottom layer faster than the top. Sometimes useing a teflon foot will help, but using pins to guage the progress on a long seam is helpful.

Marilynn
June 12th, 2008
9:04 PM

Could you divulge a few “secrets” to sewing without pins? I often start sewing at a critical point and sew away from it, pushing any extraneous fabric into the seam. Is this a good idea? I noticed in your sample that you were using polar fleece which stretches ALOT with the pressure of the machine. Could you speak to other types of fabrics? Thanks so much.

Mia
June 13th, 2008
5:46 PM

You have opened my eyes to the problem I encountered many times. I have always wondered why some of my patterns didn’t sew up properly when I knew the pattern I drafted was accurate. Now I have to go buy some weights. What type do you suggest?

AJ
November 10th, 2009
5:50 AM

Just wanted to make a comment as I can tell from the confused comments that some people haven’t quite got it. Kathleen is namely talking about not using pins when you are cutting the pattern out. If you use pins the fabric can end up shorter and then when you go to sew it will not be the right length and you will have problems with things not lining up.

As far as sewing without pins, this is easy to do if your patterns are cut properly and you have learned how to not mis-handle the fabric. For someone who is new to sewing, or is not new to sewing but is heavy handed with the fabric, if you do not use pins as you sew you can stretch one or the other layer of fabric ever so slightly and have bad results. Also, most of us are working off of home sewing patterns which are not perfect. Discrepancies will exist for a variety of reasons, some of which are: Your error in cutting out the pattern (did you cut on the line, on the outside of the lines, or inside the lines?), your error in cutting out the fabric, the company’s error in the actual pattern, and patterns that are made as home sewing patterns which require easing. If you are trying to sew a pattern which has been made with home sewing methods in mind, and requires easing, you laying the two pieces of fabric together without pinning them — unless you are highly experienced — will probably have a lot of problems. Kathleen doesn’t need pins when she is sewing for two reasons: 1) she’s mostly going to be sewing her own patterns which are probably perfect, and 2) if she does use a home sewing pattern she has enough sewing experience to not need pins.

Therefore, most of you will probably still need to use pins when you are sewing, even if you have become a good sewer who does not mishandle fabrics and you have learned to cut out the fabric perfectly. The reason is the home sewing pattern you are using has been made expecting you to pin and mark up the notches and manhandle the fabric so that the fabric fits between those notches even if they are not equal lengths.

If you want to start sewing without pins completely either learn how to draft your own perfect patterns or learn how to modify those home sewing patterns so that everything lines up and ease is not needed — there are various ways to do this but the hint is that the length of two seams should be equal if they are to lay flat and should be a bit different depending on the weight of the fabric if one is to go on top or inside of the other.

Hope that cleared up some confusion for future readers and anyone who made the previous confused comments. For the record, I may have this theoretical knowledge but I still need either pins or basting when I sew home sewing patterns too.

[…] should exactly match the shell they folded back onto but I suspect this is what Claudine did. Keep ID and OD in mind. Pieces that turn to the inside should be slightly smaller than the piece they’re […]

[…] Forum « Japanese dress forms I.D. and O.D. […]

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