Two things decide whether a seam holds: the thread weight and the bobbin style. Thread you pick by what you sew. The bobbin you do not pick at all. Your machine already decided, and the wrong one stops the machine or skips stitches.
The lookup
Which bobbin does my machine take?
Bobbin style is a property of the hook, not a preference you get to express. Find your model below. If it is not listed, measure the bobbin you have against the dimensions in the next section before you order anything.
| Machine | Bobbin | Why |
|---|---|---|
| JACK F5-HL-7, F6-HL7, H2, H5, H6 | M | Walking foot heads built around a double-capacity bobbin. H5 and H6 are discontinued. |
| JACK H7-C | M | AI walking foot, same double-capacity hook. |
| SPEEDWAY SW-0303L, SW-335L | M | Heavy duty walking foot, flat bed and cylinder bed. |
| JUKI DNU-1541, DNU-1541S, DU1181N | M | Unison and top-and-bottom feed walking foot. |
| JUKI DDL-8100eH/X73141 | M | The heavy-duty large-capacity DDL. The standard DDL flat beds do not take M. |
| CONSEW 206RB-5 | M | Unison feed walking foot. |
| Dürkopp Adler 168, 267, 269, 286 | M | Documented by the bobbin standard. |
| Pfaff 545, 545-900, 1245-706 | M | The 1245-706 takes M. The plain 1245 takes G. |
| Juki DDL-201, DNL-9000, MOL-500 | M | Documented by the bobbin standard. |
| Longarm quilting: APQS, Gammill, Handi Quilter | M | M holds the most thread, which is why longarms use it. |
| SPEEDWAY SW-810, SW-810D, SW-820, 818D | G | Post bed lockstitch, single and double needle. |
| SPEEDWAY SW 9910, SW591-Q | G | Post bed triple feed. |
| JACK S7-91T | G | Post bed triple feed. |
| JACK T2210, T3020 | G | Programmable pattern tackers. |
| Consew 225, 226, 227, 277, 287, 290 | G | Documented by the bobbin standard. |
| Dürkopp Adler 67, 67-FA2, 267-VG, 268-VG | G | Documented by the bobbin standard. |
| Singer 168-G101 | G | Documented by the bobbin standard. |
| Juki LH-512, LH-1152, LH-2178, LU-562, LK-1910, APW-116 | G | Twin needle, unison feed and bar tack. |
| Pfaff 1245 | G | The plain 1245. The 1245-706 takes M instead. |
| SPEEDWAY BC-1501, BF-1500 | L | 15-needle embroidery heads. |
| Brother PR-series | L | 6-needle and 10-needle embroidery. |
| Juki DDL-105 through DDL-5550, DDW-92, DLM series, DNL-415H, DNL-416, DLU-460, TL-98, TL-98Q | L | Standard flat bed lockstitch. |
| Dürkopp Adler 296 | L | Documented by the bobbin standard. |
| Janome, Bernina, Tajima, Barudan embroidery | L | Domestic and semi-industrial embroidery heads. |
Three styles cover that whole list. Style M is bonded nylon 66 and the largest of the three. Style G is the same thread in a shorter, narrower body. Style L is filament polyester rather than nylon, which matters more than it sounds: embroidery and flat bed lockstitch want a finer, softer bobbin thread than upholstery work does.
Can I use a Style L where a Style G belongs?
No, and the reason is smaller than most people expect. The difference between the three styles reaches 1.2 mm in diameter and 2.7 mm in height. That is enough that the wrong bobbin either rubs the hook and stops the machine, or rattles in the bobbin case and skips stitches. Neither failure announces itself as a bobbin problem. You will spend an afternoon adjusting tension first.
| Style | Diameter | Height |
|---|---|---|
| Class 15 | 20.70 mm | 11.81 mm |
| Style L | 21.26 mm | 9.12 mm |
| Style G | 21.87 mm | 9.91 mm |
| Style M | 25.98 mm | 11.05 mm |
The mistake almost everyone makes
A Style L looks like a Class 15, the bobbin most domestic machines use, and the two get ordered interchangeably. They are not interchangeable. Class 15 measures 20.70 mm across and 11.81 mm tall; Style L measures 21.26 mm across and 9.12 mm tall. It is wider and nearly 3 mm shorter. Dropping a Class 15 into a machine built for Style L leaves the bobbin sitting proud in the case, and the first thing you notice is skipped stitches on the underside.
Dimensions as published by The Thread Exchange and WBC Industries.
Thread, part one
Polyester or bonded nylon?
Bonded nylon is stronger for its diameter and more abrasion resistant, and the bonding agent keeps the plies from fraying at sewing speed. It is the standard for upholstery, leather and canvas worked indoors or under cover. Spun polyester holds up better to prolonged sunlight and moisture. For anything that lives outdoors year round, use polyester, or use a UV-treated bonded nylon that is built for it.
That single choice narrows the field faster than any spec sheet. Garment work, home textiles and anything that goes through a washing machine: polyester. Furniture, car interiors, bags, belts and covers: bonded nylon. Awnings, boat covers and patio furniture: polyester or the UV line, because standard nylon is the one that gives out first in the sun.
Two weights cover garment work
Tex 27 is the general-purpose weight of the garment industry, a 40/2 spun polyester for shirts, dresses, children's wear, curtains and bedding. It is also the weight most overlock and coverstitch machines are set up to run. It comes on a 5,000 m production cone for shops that sew one colour all week, and on a 2,500 m cone for sampling rooms and alterations, where a colour gets used once and then sits.
Tex 60 is the step up, a 20/2 spun polyester for light upholstery, bag making, light leather goods, denim and workwear. The rule is simpler than it looks: drop to Tex 27 for regular garment sewing and overlocking, and go to Tex 60 when the seam should be visible or the fabric is heavier. Topstitching is the obvious case.
Five weights cover upholstery
The bonded nylon range runs from Tex 45 through Tex 70, Tex 92 and Tex 135 to Tex 210. Tex 70 is the one most shops buy, and it is worth knowing why: it covers furniture and automotive interiors, bags, belts and marine canvas, and it is the heaviest commercial size a sturdy domestic machine will still pull. Below it, Tex 45 is for fine leather and light upholstery. Above it, Tex 92 and Tex 135 are for work where Tex 70 starts to look thin, and Tex 135 is also offered on a 1,000 m cone for runs long enough that spool changes cost you time.
Tex 210 is the end of the range. Harness, slings and load straps, sailmaking, sole leather and industrial saddlery. If you are asking whether you need it, you do not.
Thread, part two
The needle has to match the thread
Thread size sets needle size, and getting this wrong undoes everything above. Tex 27 wants a Nm 70 to 80 needle. Tex 60 wants Nm 100 to 110. On the bonded side, Tex 45 wants Nm 90 to 100, Tex 70 wants Nm 100 to 130, and Tex 210 wants Nm 140 to 180. What the needle size does not tell you is the system, which is set by your machine rather than by the thread. We wrote that up separately in industrial needle systems explained.
One warning about the numbers. For thread, Nm means 1000 divided by Tex, so Tex 70 is Nm 14.3. For needles, Nm means the blade diameter in hundredths of a millimetre, so Nm 110 is 1.10 mm. They are the same two letters describing entirely different things, and spec sheets rarely say which one they mean.
Why prewound instead of winding your own
A factory winds under controlled tension, which puts more thread on the same bobbin than you can manage by hand and keeps that tension even from the first stitch to the last. That is the whole reason production shops stopped winding. The second reason is arithmetic: a bobbin you wind yourself costs an operator two minutes, and two minutes several times a day is a real number by the end of a month.
One rule when you mix them. The bobbin thread does not have to be the same brand as the top thread, but it should be the same fibre and the same size or one size finer. Polyester on top with nylon underneath gives you two threads that stretch and shrink differently, and the seam puckers or the tension drifts a week later.
Talk to a specialist
Send us your machine model and what you sew on it, and we will tell you which bobbin it takes and which thread weight belongs in it. If the answer is a size we do not stock, we will say so. Write to contact@suprasewing.com or call (954) 681-3894.