Bobbin thread usage calculator?

[Sugarkryptonite]

Hi guys,

I have a Singer 111w153 machine and need to sew something that is over 20ft long. I was wondering if anyone knew how much I could sew with 1 bobbin on 5 SPI with this machine. I believe it is a class G bobbin.

[nylonRigging]

How many 20 Ft. runs you sew with a bobbin of thread,  ? . with sewing stitch run, 5 spi , ???
What size of thread ? are you rolling onto a Bobbin ? ,  How full do you wind your Bobbins ? ,  How long length of thread tails, do you pull to cut at the end of each stitch run ?
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[Uwe]

Option1: Just try it out:  Sew 1 foot long stitch lines on a scrap piece of same thickness and count how many runs back and forth you get. If you get more than twenty runs, then you’re good.

Option 2: ballpark it: take a fully wound bobbin, unwind it and measure how long the bobbin thread is. If it’s more than twice your stitch line length (40 feet in your example), then you should be good when sewing at 5spi.

Option 3: Math

Every stitch uses up one material thickness worth of bobbin thread (it turns around in the middle for the knot). So at 5spi you add five times the material thickness to your thread usage for every inch sewn. At 10 spi, you add ten times the material thickness per inch sewn, etc. Without getting into too much detail about unit conversion and terms cancelling out, here’s an example:

If you’re sewing something that’s 20 feet long and 1/5 inch thick, then you’ll need roughly:

1’ for lead/tail, plus 20’ straight line, plus 20’*5spi*0.2”material=20’, which all adds up to about 41 feet of bobbin thread

Edited January 5, 2022 by Uwe

[nylonRigging]

Your Question in your Post, ..." I was wondering if anyone knew how much I could sew with 1 bobbin on 5 SPI with this machine ".
 'On average'  How many 20ft. runs can you get from one bobbin of thread ? .  your question revolves around ' knowing how many yards is on your full Bobbin ' . Then
What Uwe, is saying .. figure out how many inches length, you can sew with a yard of Bobbin thread . Then 'know' how many yards are on a Bobbin your filling .

Your question is something I never ever thought about finding , so out of curiosity I put a Yard ( 36") of bobbin thread in a 111 to see ? . with t70/69 , and 5 spi .  with having a 2 inch of loose thread tail , I sewed about ( 28.5 )  inches of stitch length , for 36" of bobbin thread .
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[Handstitched]

This is something I've never considered. For large jobs, like shade sails etc. I'll have 3-4 bobbins full of thread for the job. If I need more,  and as one is used up, I can then put  the empty bobbin  on the winder and fill it up again  as I sew .

I just add enough to the invoice to  more than cover the cost of the thread . 

Quite handy having more than two spools of thread of the same colour    

HS

Edited January 5, 2022 by Handstitched

[kgg]

I like Uwe suggestions if you really need to know. If the seam is longer then what your bobbin can do either go down a size or two in thread size or when you run out of bobbin thread restart you seam a few stitches back from where you ran out and sew over the end of the original seam to finish the seam run.

kgg

[DrmCa]

  On 1/5/2022 at 4:53 AM, Uwe said:

Every stitch uses up one material thickness worth of bobbin thread

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With ideal tension, mind you. If the upper tension increases, the lower thread utilization follows, and vice versa.

[Wizcrafts]

I looked up prewound bobbins on Wawak.com, where I buy zippers and leather tape, and the Size G bobbins contain 30 yards of #69 (T70) bonded nylon thread. If the job calls for #69 thread, it will sew about 90 feet, minus starting and ending wastage. I would guess you would lose a yard or two on the ends.

A prewound bobbin with size 92 thread contains 25 yards. I'm thinking a steel G style bobbin loaded with #138 thread might only hold 12 yards of bonded thread. You might get the same, less, or maybe more thread on a tightly wound bobbin. The windings would have to be precise.

Since I sew for a living, I buy boxes of prewound bobbins in style G. I have three machines that use those bobbins. Some are b69 and others are b92.

[nylonRigging]

  On 1/5/2022 at 1:17 PM, DrmCa said:

With ideal tension, mind you. If the upper tension increases, the lower thread utilization follows, and vice versa.

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And In a Ideal World , Both bobbins on my double-needles would always end-up empty, exactly same every time. ...LOL
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