Sewing Machine with Straight Stitch Needle Plate
in place on Sewing Surface
They are custom to each machine and manufacturer, so you can't just buy a new needle plate and expect it to fit on your machine. You should go to your machine brand dealer, although there may be a few available at general sewing stores, for most popular manufacturers and models.
I have two needle plates for my Pfaff 2046. The default plate, which came with the machine, is the zig zag plate. The straight stitch plate came with the Quilters Tool Box - an accessory kit that you have to buy separately. You probably can buy the plate only from a Pfaff dealer.
This tutorial will cover what you need to know about needle plates.
First, you need to understand that not all sewing machines provide a variety of stitches. In fact, early machines merely did a straight stitch; that is, the needle only moved up and down as you sewed. It was not possible to have the needle move side to side.
As machines evolved and technology improved, other stitches became possible. These stitches required the needle to move side to side as well as up and down; the most basic is the zig-zag stitch. Almost all modern machines have zigzag, anymore. Now, patterns assume your machine can do this.
Early machines only had a little hole for the needle to pass through to engage the bobbin and complete the stitch. This hole is present on a straight stitch needle plate.
Straight Stitch Needle Plate
Zig Zag Stitch
When a machine forms a zig zag stitch the needle alternates to the left and the right with each stitch. Obviously, there must be a way for the needle to pass through when it's off center. The zig zag needle plate was born! It has a wider opening for the needle to pass.
Zig Zag Needle Plate
Comparing the Two
In a comparison of the two needle plates, you can see the difference. In the straight stitch plate, the opening is a small hole (left plate). In the zig zag plate, the opening is a narrow slot.
While it might not seem significant, it is.
Think about it: if you have a straight stitch plate on the machine and your needle moves off center, the needle crashes into the plate. It can't pass through, because the needle "missed" the hole. The zig zag plate is more versatile. It lets you make all of the stitches your machine can do. This is why the zig zag plate is currently the default needle plate.
So...why would you even bother with a straight stitch plate?
In a word: precision. Most of the time, you use a straight stitch, and the smaller opening supports the fabric as much as possible. When the needle passes through the fabric, it encounters the resistance of the fabric and pushes it just a little bit through the plate before it pierces it. With more support from the needle plate, the fabric is distorted less and thus makes a neater, more precise stitch. On a zig zag needle plate, there is a bigger "hole" (slot, really) and the needle can push the fabric through a little more before it pierces the fabric.
For a lot of sewing, this doesn't really matter too much. But, if you are using delicate fabric, or if you need seams to match up precisely, or if you require a "perfect" quarter inch seam (as needed for complicated patchwork), it makes a difference.
I use the zig zag plate for most of my sewing, but when I'm doing a project where precision counts and I'm using a straight stitch, I change the plates. Additionally, the straight stitch plate helps with stitch formation in free motion quilting. Free motion work is merely a straight stitch with the fabric being moved manually in any direction. The extra support of the straight stitch plate helps keep each individual stitch aligned properly while the movement of the fabric exerts pressure in different directions on the needle and thread.
Changing the Needle Plates
Now you can see why you need removable and interchangeable needle plates. In most machines, plates are made of durable metal, and they snap into the sewing surface. On my Pfaff, I use a little tool that came with the machine to pry off the plate.
The flat tip (to the left) tucks under a little notch in the sewing surface, and when you apply pressure to the tool, the plate pops off. To insert the other plate, you line it up in the face of the machine and press down until it snaps in place. I imagine you could use a screwdriver, but I worry that could damage the plate.
Other Features of a Needle Plate
The numbers and lines to the right of the needle hole are seam allowance widths. (a) Line up the edge of your fabric with the line labeled 1/2, and with a straight stitch in center needle position, you will have a half inch seam allowance (that is, you are sewing one half of an inch in from the edge of the fabric). Since I'm in the United States, the measurements are in inches, but the numbers below the inches are metric in centimeters. (b)
The rectangular slots around the needle hole allow the feed dogs to reach up from below and grab the fabric to pass it through the sewing surface. (c)
The rest of the openings, I'm not so sure about. I imagine they are for specialized sewing techniques. However, the large notch above letter "a" above is for snapping into place on the sewing surface.
Hope this has been helpful information for you. More sewing machine tutorials to come!