Can I have any info on singer industrial sewing machine 660a2

It is an industrial machine and suitable for leather, so I reckon you can use any thread you want. Seems it is a 191 D300A

https://www.google.com/search?safe=off&rlz=1C1QJDB_enCA643CA644&sxsrf=ALeKk03ofduDBUiaUauroZKdpZ1bFKp1Sw%3A1613518603191&ei=C1csYMKFC6uAtgW-3LS4BQ&q=singer+191+d300aa+thread+classification
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Service and Owner's Manuals

Singer 191D Lockstich ' Instruction Manual and ... - Singer.com

https://www.singer.com > default > files > outdated_product
PDF
Read all instructions, take care of this manual, and use it as reference when necessary. Page 5. 2. High Speed Straight Lockstitch Sewing Machine ' Instruction ...

SINGER 191D SERVICE MANUAL Pdf Download ' ManualsLib

https://www.manualslib.com > ... > 191D -

View and Download Singer 191D service manual online. 191D sewing machine pdf manual download.

Instruction Manuals - Singer

https://singerco.com.au > Support

Singer Instruction manuals for new and old sewing machines and appliances. ... Singer 15-88, 15-89 and 15-90. Singer 66k. Singer 99 ... Singer Industrial 191D. You've visited this page 2 times. Last visit: 06/03/20

When you thread the top thread, the thread will drop down on the right side of the tension mechanism and go around the bottom (clockwise) and up the left side. Grab the thread somewhere above the tension mechanism with your right hand and then pull the toward the right (as though you are going to close the circle around the tension disk. The thread should pull on the metal wire (spring) and your thread should pop into the correct position of the tension disk. When you release the thread, the wire spring should pop back to the left. Then you will continue threading through the remaining thread guides and the take-up lever.

Here's a service manual for your machine (in case you need one):

Singer 20U31 Service Manual

Threading video:
Threading Singer 20U 20 33 industrial sewing machine

Singer 20U Industrial Sewing Machine Tutorial

Singer 20U Industrial Sewing Machine Tutorial

Bobbin winding on the Singer 20 33 or 20U

this video shows threading the tension disk:

How to Thread Singer Industrial Sewing Machine

This sounds like an industrial machine. Go to the Singer website and click Support, then Industrial Product Support. They offer Parts Lists, Instruction Manuals and Service Manuals for industrial machines. If you can't get an instruction manual, you can often get a service manual.

https://www.google.co.uk/webhp?sourceid=chrome-instant&rlz=1C1CHBD_en-GBGB719GB719&ion=1&espv=2&ie=UTF-8#q=how+do+I+replace+the+v+belt+on+a+singer+251.2+industrial+sewing+machine%3F try this link

Check out these search results:

Fuzhou Antyco Optics Google Search

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How do you thread up and wind thread onto a industrial singer sewing machine model 195KI

Problem with sump or with sump screw? Or overly full?
I'm currently refubishing a Singer 491. To understand what sump and sump screw are, check out the YouTube channel of becauseimcrafty for their instruction on changing the oil. This demonstrates the large oli pan of a Singer industrial machine that is similar to yours as far as the oil "pan" or "sump" goes. TItle of their video is <<Industrial Sewing Machine l Changing the OIL>>.

Not sure if link allowed here: https://www.youtube.com/watch?v=yIF8npj-VLk

hi roslyn.
not sure if you have the manual,but go to this link might help you out with it.
manual singer 20u33 industrial sewing machine Google Search
and again not sure if this link will help you out.
its all i could find on the internet.
singer 20u33 industrial sewing machine bobbin case problem Google Search

You can find parts charts and instruction manuals for industrial Singer machines on their website parts.singerco.com.

Visit parts.singerco.com for industrial manuals.