Author Topic: Mixing thread sizes - Top & Bobbin  (Read 121 times)

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ultimind

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Mixing thread sizes - Top & Bobbin
« on: April 06, 2018, 09:58:51 AM »
I've put together several packs lately that have contrasting topstitching (such as along a zipper) in T-90 bonded nylon with a T-70 bonded nylon bobbin thread. My non-scientific testing shows that the stitch is perfectly centered in the material and it holds up as well as using T-70 top and bottom.

Are there any negatives to mixing top thread and bottom thread of different size? T-90 and T-70 work well so far but could I get up to T-135 topstitch with T-70 bobbin?

I'm sure there are large scale efficiency problems with doing so but I'm a one-man, part time hobbyist operation. I want to have the ability to have a nice prominent topstitch but without the hassle of having to have a bunch of different bobbins especially for a color that I may only use one time. I use enough black T-70 to buy 16oz cones but I'd prefer to get 2-4oz cones when I need something like bright purple or neon orange topstitch.

StonePhotoGear

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Re: Mixing thread sizes - Top & Bobbin
« Reply #1 on: April 08, 2018, 01:47:02 AM »
I do it from time to time, but only for decorative topstitching. Seam strength is only dictated by the smaller(bobbin) thread, not the larger(and stronger) top thread.

SARK9

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Re: Mixing thread sizes - Top & Bobbin
« Reply #2 on: April 08, 2018, 06:59:17 AM »

[...]Are there any negatives to mixing top thread and bottom thread of different size? T-90 and T-70 work well so far but could I get up to T-135 topstitch with T-70 bobbin?



I use a good bit of black fabric (usually 1000D) on machines that will run T-90 or T-135 top thread, but are cursed with small bobbin capacity (mostly G, but sometimes L or A style bobbins, or the miniatures used with 29K style patcher machines). I use T-45 Kevlar thread in the bobbins to roughly match the tensile of T-90 poly (14lbs vs 14.5lbs) so that is a good match on paper, and T-70 Kevlar is a match for T-135 poly. Vastly more T-45 fits on a G bobbin. Mostly this is useful for assemblies where the bottom stitch is hidden, inconspicuous, or absolutely pragmatic, and the color selection for Kevlar threads is....not good. I don't find the appearance on black to be all that objectionable, but of course that is subjective. Also, any remaining thread tails cannot be burnt or melted, and you'll want sharp scissors, but certainly not your favorites. I've *not* used it for lower thread on a machine with an automatic undertrimmer.

-D

ultimind

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Re: Mixing thread sizes - Top & Bobbin
« Reply #3 on: April 08, 2018, 03:42:07 PM »
Thanks all for the insight. Hadnít considered using Kevlar thread. Thatís an interesting way to go about it. I would think the scissor dulling would make most shy away from it. Iíve been using a lot of Dyneema gridstop lately and the UHMWPE fibers are killer on my scissors.

Globe

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Re: Mixing thread sizes - Top & Bobbin
« Reply #4 on: April 18, 2018, 12:54:18 PM »
It's recommended to only use Kevlar thread with more Kevlar thread and fabric. It is extremely abrasive and will eventually cut nylon.