Fabric Weight / Typical Thread Sizes / Needle Sizes

A long time ago I had an interesting long discussion with an elderly techie at a sewing supplies company. I think his job was to sort out customers’ sewing problems. Well, more of an hour long lecture than a discussion.

He made several points. First, in general, commercial sewing companies usually used a needle which was about two sizes bigger than needed, just to avoid any thread problems and needle breakages. In general this did no real harm as the threads reverted to their ‘right’ positions quite easily. So this sort of needle oversizing tended to be found in ‘recommendations’ these days.

Second, since most people don’t look very closely at the sewing, most companies use a thicker thread than they need to, for similar reasons.

Third, some companies use a lock stitch (two threads), but other companies use a single-thread chain-stitch or misuse a serger, to get higher sewing speeds. The problem with a chain-stitch is that a single thread break can see the entire seam unravel in seconds.

However, and this is a crucial point, these practices applied to UNCOATED woven fabrics. When you switch to coated fabrics there are other concerns, such as the coating and the displacement of the fabric threads.

I have never been very keen on Gutermann thread: I prefer Amann Rasant myself, but the manufacturing scene in USA is so poor that  Amann can’t be bothered marketing there. Yeah, I’m serious.

Can I suggest you try a lighter thread? For reference, I use a #60 needle for both Rasant 120 and Rasant 75 threads on silnylon. I only use the Rasant 75 on really critical seams whch take the highest loads. For the rest Rasant 120 is fine. And yes, I make my own tents, packs, quilts, raingear and clothing.

Cheers

PS: NEVER ever use a pure cotton thread on outdoors gear. It rots.

I use both Mara 70 (T-40) and Mara 100 (T-30) along with other types, sizes of thread.

For me T-40 and #80 needle sews well.  T-30 and #70 needle sews well.  Just as you have found.  The eye and groove in the #70 needle is too small for the T-40 thread.

For the thin fabrics I personally like the Tex 30 thread.   Be happy with thinner thread and nice stitches.  If you have an area that you think needs more strength you can always do two lines of stitching or switch to the thicker thread & needle.

For needles I use Schmetz brand Microtex (sharp) or Jeans needles.  The Jeans needles have a stiffer shank so flex less but may be hard to find in the #70 size.

-Ken

Thank you Roger, too bad we can not find the same thread that you use here in the US.   I will follow your suggestion an try even smaller needles / thread so see how it works on fabrics even lighter than Silpoly 1.1 (i.e membrane or 7D sylnilon).

Ken, thanks for confirming my findings.  I’m farily new to sewing and work on a entry level machine so i was not sure if my findings were “user operator”.  It would be really nice if RBTR starts offering MARA 100 or lighter to complement the lighter fabrics they are bringing to the market.

Per Gutermann’s specifications recomendations of neede size:
– MARA 70 (Tex 40):  Needle size 90/14-100/16
– MARA 100 (Tex 30):  Needle size 70/10-80/12
– MARA 120 (Tex 25):  Needle size 70/10-80/12 (Same size than for MARA 100, I wonder what would be the benefit of using this thread)-
– MARA 150 (Tex 20):  Needle size 65/9-70/10

All this MARA threads can be found online at wawak at very reasonable prices (Much cheeper the Joanns) and in a variety of colors.

Thumbs up for Wawak.  They are also my main source of thread with fast service and some of the lowest shipping cost for here in Ohio.  And they list the Tex numbers for threads!

Some may wince but I also find Coats and Clark Dual Duty XP General Purpose Thread (Tex 30) sews well for me (WalMart).  It is a poly wrapped /poly core that works well with some fabrics.  Different lubricity I guess.  Gutterman Mara is a spun filament polyester and I cannot find any fault with it.  Some don’t like it though so it might depend on what your machine likes.  Amman says their Rasant line of thread is a cotton wrapped / polyester core.  I perfer all polyester but the cotton wrap might be why it sews well with Roger’s machine.

These slippery fabrics of silnylon, silpoly, PU, sil/PU hybrid may all sew different with different threads and different machines.  All you can do is expeiment.

-ken   5-7-16

The original point of a polyester-core with a cotton wrap might surprise you. Obviously the poly core is for strength. The cotton wrap was (and still is) to insulate the poly core from the needle. When sewing in a commercial use at high speed the eye of the needle can get quite warm, which softens the polyester, and in extreme cases it can even start to melt the polyester fibres. Instant tangle and broken everything. Also, I believe the cotton fibres give a bit less friction through the eye.

I also find the cotton wrap useful when seam sealing: it is easier for the silicone sealant to lock into the cotton fibres. A minor point.

Another point not always understood is the ‘twist’ in a thread. A poly-cotton thread is a bit softer and more flexible and does not kink. A tightly spun straight polyester thread is a bit stiffer and harder, and in some machines it can develop kinks or twists while going through the tensioner and needle. This can cause all sorts of problems.

For Mario: it may be that the Mara 120 is the same weight and strength as the Rasant 120 – there are several gauges for measuring thread. I always use a #60 needle with the 120 – see my previous comments about over-size needle recommendations.

OH MY.  This has now totally stressed me out and paralyzed my pyramid making.

I bought the smaller needles, the microtex sharp ones, 70/10 to use with the silpoly I got from RSBTR.

But now should I not use the Gutermann 70 they sent with it??  Do I need to buy new thread???!!!!

try what you have, will probably work

while you’re at it, do some long strips and see if they slip relative to each other

I’ve always used Gutterman from fabric store without problem

Jennifer, if you are getting nice/even stitches with the 70/10 needle – MARA 70 thread combination you don’t have to worry, and as Jerry said, if you try with some scraps you will quickly find out.  I suggest you try with the same number of layers you are sewing (i.e if you are doing a double rolled hem on the perimeter or a flat fell seam for joining your panels… try sewing 3 layers of fabric).

if you are NOT fully satisfied with the stitches you are getting, MARA 100 is the same than Gutermann “Sew-All 100% Polyester” available in Joanns or other major “brick & mortar” stores you may have close to where you live.  Unfortunately the color numbers of “Sew All” and Mara 70 do not correspond so you will need to make a visual match.  On the other hand if you don’t mind to wait a couple of days you can order from WAWAK, they do carry MARA 100 & MARA 120  and they do have a wide variety of colors.  Their color numbering match the one that it was sent to you by RBTR and shows in the spool.  They have a very quick shipping, they shipped the same day I ordered my spools.  Their prices are also much better than Joanns (i.e $2.45 for a 1094 yds spool)

Jennifer…  No stress please.   I just ran some Gutterman Mara Tex 40 with a Microtex 70 needle through 2 layers of some sil nylon at a slow speed and it did just fine.  I would have to increase the upper tension up a bit to balance out the top and bottom.

I mentioned above that I prefer a #80 needle with the Tex 40 thread but I didn’t say it won’t work with a #70.  The Tex 40 is probably a bit heavy for thin fabric but as Jerry mentioned you just have to experiment on some scrap fabric til you see what combo works for you.  I don’t have any of the sil-poly to try so I don’t know if it’s sewing properties are different.

I do not understand why RSBTR includes the Tex 40 thread.  It’s a good thread but just heavier that what is probably needed for these thin fabrics.  A Tex 30 would be more appropriate (in my opinion).

-Ken

Hey Mario – thanks.  I was thinking of doing that, and I saw how nice it was they gave me the color number!

Would you guys suggest that I get the 100, or the 120?  I’ll be using the Silpoly MEMBRANE .93 and the Silpoly 1.1, as well as the PU4000 for the floor.

Jennifer, I haven’t tried the MARA 120 / Needle 70/10 combo yet, but my thread order from WAWAK is in transit.  As soon as I get it, I can do some testings and report back on difference between MARA 100 & 120.  (I do have Silpoly 1.1 PU4000 fabric on hand).

Hi Jennifer

It’s not a problem. As long as there is no glaring mismatch, just make the tent and try it out.

Evil chuckle: it won’t be your last MYOG, and there will be plenty of time to refine your selections…. :-)

Cheers

Jennifer, I just tried again the needle 70/10 with Mara 70 (Tex 40) thread combination and the stitches are coming out OK. I haven’t been able to replicate the bad stitches I got when I originally posted this message. What I’m thinking is the first time around when I was testing some scraps using for the first time that thread / needle combo I probably inserted the needle improperly and this is why i got bad stitches, this is also why the stitches did not improve as I played with different tension settings. Then when I CHANGED to a thicker NEEDLE (80/12)  and left the same thread (Mara 70) I obtained good stitches.  Then again I changed the needle to 70/10 and and tried with a spool of Mara 100 thread and got good stitches.  This lead me to believe the problem was a mismatch between the size of the eye of the needle and the thread thickness.   But being new to sewing i posted this question to find out other folks experiences with MARA 70 which since is provided as a freeby the RBTR I assume has been widely used.

Have you tried yourself the 70/10 needle with Mara 70 thread combo in your machine sewing a scrap of  silpoly 1.1oz PU4000?

Roger, thanks for your suggestion of using a 60/8 needle.  i did some testings last night and from my benchmark of having a non-reinforced double rolled hem tear at the seam line at 25 lbs with 70/10 needle, it went up to 40 lbs when I switched to a 60/8 needle, even when using a thinner thread like MARA 150 (Tex 20).  Again the failure happen by tearing off the fabric at the stitch line of the hem.  All this is working with silpoly 1.1oz PU4000 which supposedly has a lower tear strength that other fabrics like silnylon due to its mixed coating (sil in one side & PU on the other side) and the low sttretch of the base fabric (Polyester vs Nylon).

Hi Mario

Good feedack, thanks.

Yes, the PU coating does reduce the strength. The PU coating may go sticky after a while – sometimes it does, sometimes it does not.

You could try using a longer stitch length to get a higher tear strength. That would be interesting.

Cheers