You have to know this before you get anywhere near the welt pocket project. When you’re learning something new, everything can seem equally important and you may not be sure which concepts are your real priorities. Another problem is if you mis-prioritize something here because it is similar to something you already know or you think that you already know how to do it well. Whatever. I don’t know how to make these things stand out in your mind but if you don’t read another thing, read this: Your greatest priority is to mark and cut correctly which is -most likely- not the way you learned to do it.
Industrial practices place an entirely different weight on cutting. The fabrics and patterns are cut according to highly controlled standards. Cutting is much more important in industrial sewing; it’s one of the major reasons why our stuff looks better than homemade. In home sewing, cutting is a necessary and boring task you have to endure just to get to the fun part. You can’t look at it that way anymore. There is no part of patternmaking -or sewing- that is MORE important than cutting correctly. And again, correctly means placing different priorities on the task, the first of which is accuracy. To be consistently accurate -I cannot say this enough- Cut All Lines Away. Cut Them Off. All of Them. Always. No Exceptions. That thick outline is not a frame or any part of the pattern piece. It’s outlining the boundary of the piece, like a fence only this fence is not on your property; it’s on your neighbor’s. Cutting ON the line is NOT close enough. Cut it off.
In the photo above, you can see the patterns are reinforced with fusible interfacing. I did that because the tissue is too delicate for me to work with -this is a cute vintage style from the 40’s. The lines are shown cut away. If you don’t cut your lines away, whether they’re drawn on paper or traced onto fabric you’ve made your pattern that much larger -or smaller. The cutting away of lines applies every day and in every way. No exceptions.
Failing to cut lines away makes the pattern grow. For example, failing to cut the lines away on a curved neckline conversely make it smaller. Worse, a collar which is sewn into the neckline is getting bigger than its reciprocal set down seam -depending on the shaping of course.
At right is a sample illustration of a neckline traced out several times. Nearly always, a neckline is concave. If you draw around a concave neckline -keeping the shoulder line and center front static, the neckline (or a crotch line) will get smaller.
Now, at the same time your neckline is getting smaller, your collar -say a mandarin or some other sort of straightish collar- is getting larger (at right is a sketch of the end of a straight collar). So while your neckline is getting smaller, your collar is getting larger and the two will never fit together. This is one reason why you can’t grade a pattern by extending the boundaries of every edge by some determined amount. Proportionately, the concave areas get smaller and the convex or straight edges get larger.
Now on to marking.
It’s hard to explain this but when you’re measuring off a line-say adding a seam allowance- you need to place your ruler with the baseline of the ruler (shown here at 3/8) underneath the line you’re measuring off of because you can never get your pencil line precisely at the 3/8″ because the ruler edge is in the way.
So do it like this. It is a mistake to put the ruler line right on the line because the allowance would end up too big. For pattern making, I only recommend one kind of ruler; either the B-95 (below)
or the B-85 (below)
made by C-Thru. Most people use the B-85 (both are 2×18) but I don’t like it as much because the 1/8 on one side of the ruler is just a hair larger than the 1/8 on the opposite side. Any apparel industry supplier will sell the B-85’s. If your supplier doesn’t carry the B-95, you can get that at most art supply stores.
At this point -based on past experience- I get a whole bunch of mail from people protesting that their home sewing quilting rulers are just fine for this job and maybe you’re right and I’m wrong but I’m sticking with this. The quilting rulers don’t have all the divisions or have a metric side either. Plus they’re big and clunky and cost a lot more. The B-85/95’s are $2 or $3 each. I have about 6 of them. Also, these make lousy fly swatters because the ends will shatter. Don’t ask how I know that.
Lastly, these two things are the first things I ever learned in design school. I’ve been extremely dismayed and appalled to learn that many people who are much better educated than I am -with 4 year apparel degrees or better- never learned what I learned on my very first day. If you don’t cut and mark correctly, you’ll have nothing but trouble with your welt pocket. Industrial sewing is precise.