Threads Magazine will soon have my article, Industry Seam Allowances, available for download from their website. The article (issue 199, pages 40-45, currently on the market) explains how and why the industry reduces seam allowances. The diagrams show the blouse pattern seam allowances that are used in the industry.
The variety of seam allowances used when sewing shirts in industry make it possible for factory operators to sew men’s shirts at top speed. That, plus little design change in men’s clothing, greatly reduces training time. These two factors, plus off-shore factories explain why we often find shirts in the USA department stores for less than $20. However, when one makes a shirt for the first time it quickly becomes obvious that sewing a shirt is not easy.
There are the two basic ways a shirt differs from a blouse:
1. The primary difference between a blouse and a shirt is the sleeve cap. Shirts are designed for men. Men have broader shoulders and considerable strength through their shoulders and biceps (the bulging muscles on the front of the upper arm). The garments they wear need to be designed to withstand stress, especially through the sleeve’s biceps, the reason a shirt sleeve’s biceps line is considerably wider than that of a blouse sleeve’s biceps line. The sleeve’s biceps width provides the extra room in the shirt’s sleeve provides men with better upper arm fit. The armhole is lower and the circumference ease through the chest is also larger than than of a blouse, in order to provide the extra room needed through the upper sleeve and body of the shirt.
2. The second major difference is the seam allowances. All of a shirt’s seams need to withstand considerable stress. Many of the seams are flat-felled, a sewing procedure that encases the raw edges of the seam allowances. Double-needle, used to sew high-end shirts, consists of sewing each seam twice, as shown here. The side and sleeve seams are given 3/8 inch seam allowances. The first seam is sewn on two gauges shown above. As the second seam is sewn the seam allowance previously sewn on a 1/2 inch seam allowance encases the seam allowance previously sewn on a 1/4 inch seam allowance. In the industry operators use folders to sew the second seam. It is usually easier for someone at home to use a standard straight-stitch foot.
Most men are wearing shirts that don’t fit. The only real criteria is often that the shirt fit at the neck and that the sleeve cuff extend 1/2 below the edge of a blazer or suit jacket’s sleeve to save wear and tear on jacket sleeves.
Here is a listing of seam allowances used in industry to sew shirts:
Neck (shirt body) 1/4 inch
Collar,and stand: 1/4, 3/8, and 1/2 inch
Front placket: 1/2 and 1 inch
Left and right front: 3/8 inch
Side, yoke, and sleeve seams: 3/8 inch
Sleeve placket opening: 1/8 inch seam allowance
Placket: 1/2 inch, 3/8 inch
Armholes: 1/4 inch
Sleeve caps: 3/4 inch
Sleeve at cuff seam: 5/8 inch
Pocket: 3/8 inch, 1 1/4 finished hem with a 3/8 inch turn down.
Cuff: 3/16 inch around edges, 5/8 inch seam at sleeve
Hem: 3/8 inch
© Laurel Hoffmann, 2018.