Sewing machines are surprisingly delicate pieces of machinery. When the bobbin or needle gets pulled out of timing with the rest of the tool, the machine is useless and becomes a danger when the needle breaks.
In this Instructable I will show you how to adjust the bobbin timing on your machine. For my example I will be using the Handi-Quilter at TechShop San Jose.
You will need:
A pair of thread nippers
A screw driver
A metric hex key set (if your machine happens to use it. It might be all screws)
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Step 1: Take It Apart
First, remove the needle plate and run the wheel by hand to see where the needle is hitting. This can give you a good idea of which direction you need to rotate the shuttle hook and shuttle race.
Step 2: How a Bobbin Works
Sewing machines are a mystery to a lot of people, but this website has a great animation that shows how a bobbin works.
There are 2 main parts that I will be talking about today
1. The Bobbin Case
2. The Shuttle Race/Shuttle Hook
The Shuttle Race is made of 2 parts. The part on the inside is stationary, and the part around the outside rotates and grabs the thread as you sew (aka. the hook).
Remove the bobbin case and loosen the lock bolts located behind the shuttle race so you can turn and realign it with the needle.
On the Handi-Quilter, there are 2 lock bolts which you can access through the access points on each side of the machine. You might have to turn the wheel to get to each.
Now that the shuttle is loose, turn the hand wheel until your needle is all the way in the down position and just about to start on the up swing.
Once you have the needle down, rotate the outside of the shuttle until the point of the hook is just above the eye of the needle.
It is very important that the inside of the shuttle stay stationary during this alignment. It should be held in place by a prong coming out of the machine.
Now tighten your lock bolts behind the shuttle so the shuttle hook turns when you run the machine wheel.
Again, you may have to carefully turn the wheel to get access to the bolts, but be sure the shuttle is turning with you.
Next, check the distance between the stationary part of the shuttle and the pin that comes out of the front of your machine. The pin should insert into an opening at the top of the shuttle.
There should be an opening between the top of the pin and the back of the shuttle slot. It varies between machines, but should be somewhere around 1/16" or less. You really just want enough of an opening do the thread can come up through after going around the bobbin.
If you do need to adjust the distance of the pin, there should be a bolt underneath the machine you can loosen.
I suggest you thread the machine, insert your bobbin, and run the wheel to make a stitcth at this point to make sure you have the shuttle hook and your pin aligned properly.
Now, reassemble your machine and test on a piece of fabric.