I have a Singer 5050 and I can't get the pressure foot to snap on.

Hm, if you talking of a blind hem foot, this indicates that one came with the Singer One.

1 ONE Singer Sewing

It appears your machine has a snap-on foot capability, so if that is the case, a snap-on blind hem foot should work.

http://www.sewingpartsonline.com/blindhem-foot-singer-006812008.aspx

Make sure--Does the machine take a short shank presser foot? If so, you can replace it with a short shank zig-zag presser foot. You can probably go to a regular sewing machine repair shop and find a replacement presser foot.

**NOTE--the links below are examples of what is available. I cannot vouch for these vendors as I've never purchased from them. Do your own due diligence before purchasing!!!

Here's an open toe presser foot:
Open Toe embroidery satin stitch foot Low Short Shank Babylock Bro White...

or a regular zig-zag foot:
http://www.ebay.com/itm/Vintage-ZIGZAG-FOOT-Fits-Singer-Pffaff-Other-Mfrs-Low-Short-Shank-Apps-MPN-C24-/401237995786?hash=item5d6ba5f10a:g:8UcAAOSweWVXcubS

OR you can buy a short shank adapter and a kit of snap-on presser feet that will give you a big variety of different kinds of presser feet, probably including a zipper foot, hemmer foot, 1/4" quilting foot, darning foot, teflon foot, etc....(probably more than she will ever use!) The snap-on kits are available online, try eBay or some of the other sites. They most likely are not Singer brand, but are most likely generic. However, if your granddaughter is just learning, this may be the broadest variety of choices.

These are examples of snap-on presser feet available.

Snap-on Adapter example (most kits do not include the adapter):
http://www.ebay.com/itm/Low-Shank-Presser-Foot-Holder-Adapter-Snap-on-Singer-Kenmore-Juki-Elna-Janome-/222013366993?hash=item33b10722d1:g:Sa0AAOSwJb9WsRpp

Snap-on kits- examples:
42 PCS Domestic Sewing Machine Foot Feet Snap On For Brother Singer Set...

http://www.ebay.com/itm/1-Set-32-Pcs-Domestic-Sewing-Machine-Foot-Feet-Snap-On-For-Brother-Singer-Janome-/282017920492?hash=item41a993f5ec:g:MrAAAOSwMVFXH3rP

...

You should be able to find presser feet for your machine as long as you know what type of shank your machine takes. Just confirm that whatever you choose will fit a Singer model 4562. You can even purchase a snap-on shank adapter and then purchase snap-on feet for your machine.

Product Quick Search 318 335 4567

Sewing Parts Online Search

http://parts.singerco.com/CPpartCharts/4_4999 (look for 4562)

...

I suggest taking the machine to a repair shop and ask them if
they can get the part

Are you making sure the little metal bar is lined up with the little snap on grip?

your manual is here http://www.singerco.com/uploads/download/446_5040_5050.pdf

Page 12 says the whole pressure foot comes off by using the thumb screw, so not clip on and off feet.

I suspect that there is not enough pressure from the presser foot. Is there a way to adjust the pressure with a lever or a dial? And are the feed dogs up all the way? Without seeing it, I am only guessing.

Try a new needle and rethreading. Check your threading by putting the presser foot up , then pull thead, should move smoothly, now put presser foot down, now pull, it should barely move. This usually seats the thread in the tension discs.

Make sure you get a foot designed for this Singer sewing machine. Then for snap-on feet, push down slightly on the front of the foot then pull forward (with some you pull to the left). To insert a new foot, push the foot towards the connector (back or to the right) and then push the back of the foot up (once in contact with the connector) while still moving into the connector. (You should feel the spring lift up and snap around the foot.)

For shanked feet, loosen the thumbscrew and slide the open side over the screw and press against the shaft. Then tighten the thumbscrew.

I hope this helps.

Cindy Wells
(my older Singer uses a snap-on zig-zag foot. This foot gets pushed in from the front . Keep the foot below the shank until you have the bars centered around the base of the shank. Then bring the foot up and push back until it snaps into place. There is a horizontal rod between the bars and the shanks locks around that rod. The rest of the feet are shanked.)

No, the foot has nothing to do with the stitch quality. Your machine is jamming up, check your upper tension. It should be set between 3-5. Make sure the dial has not changed by mistake.