I need to change to rolling hem

Be sure you have the proper foot for your machine to make a rolled hem.

Bernette 203 How to use rolled hem foot have the one page manual but it...

Sew Inspired Serger Rolled Hem Tips

In case you don't have a manual, you may be able to glean some information here:
Sergers Overlockers
need manual for the Bernina Bernette 203 overlocker

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Consult your owner's manual. Usually, the standard overlock tension settings are somewhere in the middle of each dial, ie if the dials are 1-9, the mid-range is 4 or 5.

Here's a manual that may be helpful:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAAahUKEwijk4uUjZvHAhVVL4gKHZHFCBM&url=http%3A%2F%2Fwww.husqvarnaviking.com%2Fsitemedia%2Fproducts%2Fmachines%2Fsupport%2Fhuskylock_s15_manual_en_e.pdf&ei=5c7GVeOMNNXeoASRi6OYAQ&usg=AFQjCNF2jSaQ5fFkvSNjeWLqqA3Av42JgA&bvm=bv.99804247,d.cGU&cad=rja

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No you do not need the cutting blade to serge but you shouldn't have to remove the blade it you should be able to push the knob at base of blade inward or pull it outward to turn blade downward out of the way.

TUTORIAL - How to do a rolled hem on a serger - StitchCraft

http://stitchcraftonline.com/blog/?p=42 - 71k - similar pages Aug 5, 2009 ... One of my favorite uses for my serger is to do rolled hems. A rolled hem is were the machine folds the fabric under a tiny bit and then stitches it.

here is the Elna site, see if you can find your manual there.
http://www.elnausa.com/en-us/models_overlock.php

Bernette/Bernina Dealer will order for you

Rolled hemming on any overlocker is usually achived the following way. Right hand needle only.
Blade over to the right usually to cut wider than normal but you can vary this to suit the fabric and stitch width you want.
Thread in this needle and the upper and lower loopers. If you can source any, use woolly overlock thread in the upper looper, this fluffs out when not tensioned and covers the fabric to give the look of solid stitching. Change upper looper tension to about 2 and lower looper tension to about 6 or 7.

The lever by the plate is usually to control the little stitch finger where the stitches are formed, move it backwards and it should move back towards you?? If this happens, then you want it in the retracted (towards you) position for rolled hemming so the stitching is much smaller and the fabric can roll. Normally this stitch finger holds the fabric firm for the loopers to form the stitch over for your normal 3 or 4 thread overlock.

Now test stitch and see how it looks. Tighten the lower looper thread so it lays right beside the needle on the underside. You may need to then tighten or loosen more the upper looper, you want the upper thread to wrap all the way around to the underneath against the lower looper thread and needle.

The cut edge of fabric should roll to underneath inside your seam. Once you've got this happening, turn the stitch length down to 0.5 or so to close it right up tight. This uses heaps of thread so I usually test everything else, then close it up at the end to minimise waste.

Hope this makes sense, good luck.

Making a rolled hem on any overlocker is achieved in the following way:

use right hand needle only and top and bottom loopers. Turn stitch length down so threads are closed up (on mine this is 0.5). Your stitch length dial will be one on the right hand side near the flywheel usually. Loosen off the the top looper tension and tighten up the bottom looper tension (these are the right and 2nd right tension dials on front of the machine). On my Bernette I leave the needle at the usual 5, 2 on the top looper and 6.5 to 7 on the bottom looper thread. Move cutting blade position to the right so that you are trimming the fabric quite a bit wider than your stitch, this makes the fabric "roll" underneath inside the stitching to form the rolled edge or hem.

There is also another step that needs to happen where you change or remove a little stitch finger that sits in the pressure foot or just under it. On the Bernettes, you flick a lever to move this stitch finger back towards the operator so it is out of the stitch forming area. On some machines, it is a case of changing the little stitch finger which is screwed onto the pressure foot with a screwdriver.

I really don't know with your Necchi which it is but have a good look at the pressure foot, and around the blade cutting area and see if you can see a lever or check out the accessory bag and see if there is another stitch finger in there, it would be smaller than the one on the foot now. In effect, this finger sits out and the threads wrap around it to form your normal overlock but for rolled hem you want a much smaller finger in place to make a very little seam.

The other variable which makes a very neat job is to use a thread called "wooly Overlock" in the upper looper only. This thread when pulled under tension is tight looking but when you let it go, it fluffs out. So when seaming on a rolled hem it fills out the stitching and covers the edge of the fabric fully giving a smooth look. You can do it without but wooly thread makes a great job and you'll see it on all Ready to Wear seams usually for this reason.

If I am going to roll hem a fine sheer woven fabric like organza or chiffon I will change the needle to make sure it is nice and sharp and also ensure it is a regular point, not a ball point (I seam lots of knits so have ball points in most of the time on mine) Usually a size 80 is fine.

I hope this gets you going with your overlocker, I usually test stitch quite a bit with the stitch length at the normal 2.5 setting and adjust the looper tensions until I've got the stitch looking good, then turn it down to the very close 0.5, just to not waste a ton of thread.

You can not do a rolled hem on heavier material. It is only for thin cloth. You have to do a 3 thread narrow edge on heavier cloth.

You haven't specified your overlocker make and model but some parts of the set up will be the same; you still need to consult your machine manual to find out the changes needed to the foot. Bernettes have a little switch near the blade that you flick to change how the stitch forms so it rolls.

You need a 3 thread overlock with the right hand needle (I'm assuming you have a 4 thread lock) turn the stitch length down to 0.5 so it is very closed up. And there is usually a little thread finger on the foot that needs to be changed or a switch you flick to move it back.

Then lower the tension down on the upper looper so this thread goes over the edge to the underside and tighten up the lower looper dial so this thread lies against the needle stitch.

Move the blade to the right so the fabric is cut wider than the seam that the threads are forming so the cut edge rolls underneath and is encased in the threads.

It is best to use wooly overlock thread on at least the top looper so this "fills" in the rolled edge.

If you visit you-tube and search using "Rolled Hem" or Nancy Zieman you should find some helpful videos too.

This may be too small to read, if so, email via
www.bargainbox.com.au and I shall send it on........remember to only ever use the R needle, so you only have 3 threads.

To move the Rolled hem arm, you will need to release the upper knife (knob on left inside cover....push to the right and blade moves approx 6mm) so you can slide the small metal tongue to correct position for:

N = Normal
R = Rolled