Smaller bobbin thread for leather upholstery?

[bryanmartin]

Hi, I'm new to leather sewing obviously.  I've often heard that you should use bobbin thread one size smaller than your top thread, but this advice comes from people that sew things like quilts and garments. Does the same apply to leather automotive upholstery?  I have a large spool of #92 bonded polyester for my top thread, should I use #69 for my bobbin?

Thanks.

[Wizcrafts]

Number 92 thread has 15 pounds breaking strength. The next size down in bonded thread is #69, which has 11 pounds test. I use #69 thread, top and bottom, in thin leather, like wallet interiors and credit card slots. I also use it to sew patches onto average thickness vests. I use #92 thread for items that are between 1/16 and 1/8 inch thick. My theory is that if the work deserves the strength of #92 thread, why dilute it with a smaller thread in the bobbin? Each lockstitch is only as strong as the weakest thread.

[dikman]

Generally, people use a slightly smaller thread in the bobbin when they're trying to use a heavier thread than the machine is designed for. For example, if the machine is only intended to use #138 as the max size sometimes, on some machines, you might get away with #207 on the top and 138 on the bottom - maybe. Most normally just use the same top and bottom.

[SARK9]

I've used bonded Kevlar thread in the bobbins of certain machines for specific applications....particularly jobs which need the patcher-type machines with their miniature bobbins, as well as some of the fabric-type single needle machines with A or L bobbins. T-45 is a good match for the bigger top threads I use frequently, but getting the color selection can be problematic. Its a good option to consider.

http://www.thethreadexchange.com/miva/merchant.mvc?Screen=CTGY&Category_Code=Kevlar-Thread&gclid=EAIaIQobChMIxdOmhaev2AIVQrnACh2o1gkjEAAYASAAEgJRvfD_BwE

-DC

[Wizcrafts]

12 hours ago, bryanmartin said:

Hi, I'm new to leather sewing obviously.  I've often heard that you should use bobbin thread one size smaller than your top thread, but this advice comes from people that sew things like quilts and garments. Does the same apply to leather automotive upholstery?  I have a large spool of #92 bonded polyester for my top thread, should I use #69 for my bobbin?

Thanks.

The more I think about it, the more I suspect that you should be using #138 thread, if you can bury the knots. This should not be a problem if you're using 4-5 ounce upholstery leather. This will provide 22 pounds test per stitch, which is great for auto upholstery. The required thread strength is dependent on the stress the seams will be subject to.

If you are using 3-4 ounce leather, stick with #92 thread, top and bottom.

Use a fairly long stitch length, around 4 1/2 to no more than 5 per inch. This will avoid perforating the leather when it's under stress.

[bryanmartin]

On 12/29/2017 at 9:25 AM, Wizcrafts said:

The more I think about it, the more I suspect that you should be using #138 thread, if you can bury the knots. This should not be a problem if you're using 4-5 ounce upholstery leather. This will provide 22 pounds test per stitch, which is great for auto upholstery. The required thread strength is dependent on the stress the seams will be subject to.

If you are using 3-4 ounce leather, stick with #92 thread, top and bottom.

Use a fairly long stitch length, around 4 1/2 to no more than 5 per inch. This will avoid perforating the leather when it's under stress.

 Wonderful, thank you very much.