So what is the differential feed? In a nutshell, it controls the movement of the front and rear feed dogs under the presser foot.
Why would you need to adjust the differential feed? Because if you don’t, you may end up with puckering, gathering or stretching of the fabric – the picture below has all three of these and we don’t want that on your lovely fabric, do we?!
This why I always say to get some scraps and test the fabric in your machine, adjusting all the settings as necessary before you start sewing for real. It’s better to ruin scraps than your pretty, jersey dress – am I right?!
How do we adjust the differential feed? On my overlocker (Janome 9200D), there is a knob on the right hand side, the middle one in the below picture. Please check your manual to find it on your machine.
Setting the machine on 1.0 works well on most fabrics because the feed dogs are moving at the same rate. When I adjust it, I go up one notch at a time – to the dot in between the numbers, then up to 1.5 and so on…
If you change the differential feed below 1.0, it makes the front feed dogs move slower than the rear feed dogs, stretching the fabric. This can stop the fabric from puckering or gathering.
Changing the differential feed to higher than 1.0 will make the front dog feeds move quicker than the rear feed dogs, which gathers the fabric as it sews. This is good for sewing jersey/knits.
This fabric was called a winter jersey in the shop. It’s quite a loose weave and has a fair bit of stretch to it. I adjusted the differential feed to 1.5 and the tensions on the top two needles to 2, leaving the other tensions on 3. Below is a picture of the test I did on some scrap with these settings – perfecto!
I hope this clears up any confusion with the differential feed on an overlocker. But please do ask if you’re unsure of anything I said in this post and I’ll do my best to help!