Singer 4622 installing bobbin case

Lots of videos

https://www.google.com/search?q=install+the+bobbin+case+singer+confidence+7640

The manual

Singer 7640 Instruction Manual [Page 32] - ManualsLib

https://www.manualslib.com > ... > Instruction manual
Singer 7640 Manual Online: Troubleshooting And Maintenance. 2 4 Troubleshooting 1. Thread Loops on Underside of Fabric 2. Bobbin Thread Showing on Top of ...

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We need to know the make & model machine.

Try contacting Singer support to ask for a manual.


Singer 9140 bobbin install Google Search

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A few videos to get you started.
Install bobbin case in Singer 7463 YouTube

sounds to me like you need a professional cleaning and timing adjustment.

http://www.sew4less.com/index.php
I don't know if the link will work for the bobbin case, if it doesn't
go to sew4less.com
Bobbin Case # 52237 NB, Click for model info.
Product #: 4754

Price: $ 19.95


Bobbin Case # 52237 NB, No backlash type.
A bobbin case, also known as a bobbin holder or bobbin shuttle, holds the bobbin that is filled with thread.
Each machine has a specific bobbin case. # 52237NB
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here are is a site that have manual
http://www.sewingpartsonline.com/

Make sure the bobbin case sets sort of on top and not under the ridge of the metal ring. There is a small latch on the upper left of the bobbin case. It is metal. rotate the latch to cover the bobbin case and this should stabilize the case without making it immobile

Recheck top threading

there may be uneeded friction occuring. are you sure you inserted it correctly? sorry. photos aren;t appearing. but it may be that it is the wrong type or in the wrong place. do some trial and error and fit it into different positions on the bobbin runner

either your bobbin case isnt installed right or the machine's timing is messed up try to get needle loose or completly out is preferred then try turning it and see if it comes unjammed if so take your bobbin case out and reinstall it making sure it is in the fit right if this dont solve it then you need to get timing set (not recommended to do at home get pro to do it ) hope this helps you