More excellent information, thanks for everyone's time and input re this thread thread. Very nice to see a true experience based discussion, and to see what people have learned.
I have to give diygearsupply, listed above, a nod for actually giving all the information needed to know what the thread is you are buying. He's added navy blue recently, so that's what I'll pick up. Now if we can just nudge them into carrying standard gray... Looking through my batch of thicker threads, I realized a few things:
1. I had assumed the standard guterman you get in fabric stores, or listed as standard, what also I think quest outfitters sells as regular, was the same as the diy tex 40
but I believe if I am understanding this right that it's not.
For stronger seams, I'll try the Gutermann Tera Thread, tex 50
and see how thick that is.
I'll look for the rasant online and give that a whirl.
The thick guterman from questoutfitters, #2705 extra strong, is guterman M782
This thread is not as thick as the 30 meter extra heavy guterman thread fabric stores have (the kind with the green spool), but is still a little bit too thick to sew on a practical level with my machine.
owfinc doesn't list as clearly the type of guterman as diy, but I have bought this from them, and can confirm that their 'Gutermann 100% poly use on standard home machine, T-PG403' is also the mara 70, tex 40, same type as diy sells, I have bought from both, and the 765 yard spools have this information on them, unlike the fabric store stuff.
All nylon heavy upholstery threads, or heavy duty threads, are too heavy for this machine. Exactly as Roger noted, the Clark and Coates heavy duty is very fuzzy, my magnifier confirms this quite clearly and visibly. Although I like Naraen in Berkeley, it appears times have changed since he formed his preferences for the more rugged C&C he uses and sells.
The sewsall guterman from fabric stores is NOT the same as the tex 40 mara 70 guterman from dyi/owfinc:
100% Polyester Thread. 100 meters. Tex 30 (Tex is the weight in grams, of 1000m of thread)
And I have to admit, I cannot tell the tex 30 a 40 apart using a magnifier, but now have learned that I've been mixing the tex 30 and tex 40.
So I have a bunch of tex 30 guterman too, but that's fine for clothing.
Once I find a rasant source, I'll post links to that as well, and the mettler, which I think local fabric store may have, I'll check.
it's unclear if that's the standard mettler metrosene, another case of no information on the technical qualities of the thread, leaving it a gamble to buy it. One has to ask, what's up with some of these online vendors, they list the sq yd weight and denier of all the nylons, why no information on the threads in many cases? But kudos to diygearsupply for taking the time to actually provide the data, they are the only ones I've found so far that do.
So it sounds like it's fine to proceed with the guterman mara 70 tex 40, and I'll definitely try the tex 50 tera thread as well from diy and see how that sews. And then I supposed after I find the rasant, and discover that roger is in fact correct, I'll toss it all, heh heh...
I think this largely summarizes the information so far, unless I misunderstand something, which is quite likely since it feels like my brain is going to explode. Maybe I can return some of the threads now....
Roger, I know just what you are talking about, the joy of meeting a true expert in a field, an old timer, is always the same, you were lucky to score that, of course it wasn't luck, one of the things that gets these guys talking and sharing what they know is the fact of meeting someone who shares their life interest, but it's always a real learning opportunity, now I see why you had difficulty saying the type/brand, wholesale pro stuff is so vastly different I see now.