Singer 112w 115 timing adjustment for larger needle and stitch length changing help needed.

[DMH]

I need some helping locating information online on adjusting the hook timing on my double needle drop feed Singer 112w 115.  I'm moving to a larger needle (20) and need to know how to adjust the timing for these types of machines.   I have a needle bar that has no marks.  The instructions for this machine says it can still be done even without marks on the needle bar, but also says I should set the stitch length to 8. I'm not sure when I change the stitch length if it actually changes.  

I bought this machine from a couple on Facebook marketplace that has an upholstery business, but I have not had much luck with consistent operation since I purchased it a few months ago.  Everything from getting the right size table top from a swing machine supplier I would never use again to installing a simple knee lifter that turned out to be made horribly especially with this terribly made table top.

Edited February 10 by DMH

[friquant]

Are you changing needle systems? The photo you have above shows needle system 135x5, in size 20 / 125. Then you have a photo showing two needles of different length (definitely two different needle systems in that photo).

 

You don't need to change needle systems in order to use a thicker or thinner needle. A cursory glance at the internet did not tell me what needle system this model is supposed to take. Sometimes people do use a different needle system than called for, either because the called-for needle system is hard to find, or because they need/want more clearance under the needle. But unless you have one of these reasons to do so, I would either:

1. Use the factory called-for needle system, or
2. Use the needle system the machine is already set up to use. (Needle bar height is what you would change to swap between systems.)

[DMH]

Thanks I'm working on changing the needle bar height.

[friquant]

On 2/10/2026 at 6:34 PM, DMH said:

The instructions for this machine says it can still be done even without marks on the needle bar, but also says I should set the stitch length to 8. I'm not sure when I change the stitch length if it actually changes.  

Can you post or link your manual here?

[DMH]

I attached the manual.  I tried adjusting the needle bar height but the hook is still hitting the needle.  The needle that came with the machine is longer and I think changing to this needle system that is shorter is going to continue to give me issues.  I spent some more time online and reluctantly used chatpt and found a list of needles that should fit mt machine and give me the #20 size I'm looking for.  The needles that I purchased were not part of that list.  I found one made by Schmetz(see below) that is special order that I think will work, especially if I'm mostly using mid to heavy weight denim.  That's my next option.  

Singer 112W115.pdf

[friquant]

Wow, not much of a manual, is it? Maybe a sales brochure?

This page says your machine takes a 135x7 needle: https://ismacs.net/singer_sewing_machine_company/model-list/classes-100-199.html

This page shows 135x5 and 135x7 as being interchangeable: https://ismacs.net/needle_and_shank/pdfs/NeedleXRef9-30-23.pdf

So I expect the needles from the first photo you showed (Organ 135x5) to work fine. (No need to purchase special order needles...135x5 is a fairly common system so needles are straightforward to find)

But next up is you need to get the needle bar height (and possibly other timing issues) set correctly. This video by Uwe covers the basics of setting needle bar height: 

 

Possible reasons for the hook point to be striking the needle:

1. Incorrect gauge set installed (this sets the spacing between the two needles)
2. Needle is not oriented correctly. (Scarf of each needle must face its respective hook)
3. Hook point is striking needle either above or below the scarf (hook point should enter scarf)
4. Hook is too close to needle (hook to needle distance is adjustable)
5. Needle guard not adjusted out far enough
6. Needle is bent toward hook (Always set timing with a fresh new needle of correct system)
7. Needle with 1.6mm shank being used in a machine that is built for 2mm needle shank (Again, always set timing with a fresh new needle of correct system)
8. Axial play in the needle bar rock frame rock shaft, causing erratic left-to-right positioning of the needles. (Press the parts on both ends of the shaft towards each other while tightening the ends.)

[DMH]

Thanks for the information. This makes a lot of sense. I'm glad I didn't rush to buy those needles. You're a great resource and your information about different motor types is great also.  It will come in handy as I purchase more machines.  My next is a union special I purchased and will start working on once I get this singer working properly.

[DMH]

I followed the steps in the video you provided and made some progress.  This is two layers of denim with a little stretch. 

 

 

 

 

 

 

[friquant]

Looks like you have the left side more or less stitching

I might thread one side of it and work to get that one side dialed in, then move to the other side.  By "dialed in" I mean not skipping (check forward, reverse, short stitches, long stitches, thick material, thin material). And smooth action as the thread goes around the hook (no popping sounds, no broken thread.)

By the way, you can slide one of the bobbin case covers open and watch the hook as you stitch slowly. This can help you to understand the cause of your occasional skips. Using  a narrow piece of fabric (or just moved to one side) makes visibility easier.

 

 Someday I'll get to use a double needle 🤩

[DMH]

Your advice is always great, very well thought out.  I'm going to take those steps before jumping shifting my attention to the right side.  None of the other advice or tutorials I've tried make those suggestions.

I've only been swing since the pandemic.  I started making mask with an industrial single needle Juki and learned a lot on my own.  I learned to make jeans on that machine and now I'm trying to expand my studio with a double needle.  After this is my Juki serger and union special double needle.

I don't just want to know how to sew with vintage industrial machines but also how to service them on my own.  Patience with trial and error are the best teachers.