seiko sth-8bld-3 | Newbie Questions

[robb01]

Just picked up a seiko sth-8bld-3 with a sewing package (servo motor / speed reducer / edge guide). The machine ran excellent in the shop, but having a few issues when I got it home. This is the first sewing machine I've ever owned and have never used a sewing machine in my life, so please bear with my beginner questions

- It seems like the main belt on the machine is shredding a bit leaving rubber bits on the floor, it was squeaking too. I tried to manually adjust it by hand, and it made a little better. Should it be a very tight fit? How do you adjust the belt tension?

- Should the threads point toward the back of the machine when starting to sew? That's what it seems like on youtube videos, but the gentleman in the shop said to pull the threads forward.

- Is there a way to tell how much bobbin thread is left? How do you end/start stitching if it runs out in the middle of a run? 

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All in all it seems to be working pretty well, don't think I'll stop hand stitching smaller items. It will definitely help tote seams and seams that wont be visible. 

 

Thanks in adavance

[Wizcrafts]

The belt to the machine may be misaligned and scraping the edge of the cutout slot in the table, shredding it. If so, move the speed reducer sideways. Here's how...

There should be two bolts holding the speed reducer wheel to the underside of the table. If you loosen the bolts you can move the assembly left or right to center the belt going to the machine. There are three bolts on top of the table that position the motor. You can loosen them and move the motor left or right to line its pulley up with the reducer. Standard practice is to go from the motor to the largest pulley on the reducer, then from the smallest pulley on it up to the machine.

There is another bolt on the reducer's square shaft that hangs down, that allows it to move up or down. Adjust it for about 1/2 inch of finger deflection in the middle of the belt. There is a double nut and threaded bolt on the front of the servo motor that lets you adjust it up and down. Set it so that the belt on the motor pulley doesn't slip.

One has to wonder why these items that apparently were aligned at the dealer's shop were no longer aligned when you got it to your shop?

As for starting threads, hold them in any direction that keeps the top thread from getting pulled into the shuttle on the starting stitch or two. Unsecured threads tend to get jammed under the work and into the bobbin case.shuttle, halting the machine in seconds. Technically, you can hold just the top thread, if the bottom thread is covered by the work (vest, jacket, seat cover, etc). If you only hold the top thread, try to just keep it from being pulled down. Don't try to pull hard on it or your starting stitch will show knots on top. Holding both threads back with equal force usually centers the starting stitch. Pull the bobbin out and check it after x number of items are sewn. Eventually, you will learn to gauge how many of the same thing can be sewn with the same size thread per bobbin load.

[CowboyBob]

New belts will shred sometimes until they get the coating worn off.

Yes,hold on to the threads(esp.the needle thread) to first 3-4 stitches,towards the back or rightside.

On the bobbin thread you will probably end up knowing afterwhile how much you can sew before it runs out,but for now you'll just have to pull it out & look @ it once in a while.

[robb01]

Thanks to both, I'll try those suggestions. I loaded it onto an enclosed U-Haul trailer and drove it 2 hours to my shop, when unloading it, it looked like it hit the back door of the trailer, that's my guess for why it may have become unaligned 

[mikesc]

If your bobbin runs out..load a fresh ( with enough* thread on it for what you want to sew ) bobbin ..rethread the needle if it was unthreaded..put the item back under the foot, turn the machine by hand ( by pulling on the machine pulley towards you ..don't hit the pedal with your foot or you'll maybe snag a finger ) lower the needle into the last hole that you made before running out on the previous bobbin, now hold the thread ends as Wiz said above...next press down on the reverse lever and still turning the machine pulley by hand allow the machine to make 3 or 4 stitches backwards over the stitches previously made ( if the machine is adjusted correctly it will "backstitch" perfectly into the holes it made previously while running in a "forward" direction, then remove your hand from the machine pulley, release the reverse lever and ease down on the pedal and continue sewing like nothing had ever happened ;)

If you really want to be neat..you can unpick enough of the "run out stitching" and start from the last sewn hole with the new bobbin, leave "long thread tails" ( still need to hold them though ) and then continue..when done you can sew the ends into the holes by hand and tie ( or "melt" ) the thread ends off level with the leather..depends how neat you want to be, some people ( especially those used to hand sewing ) "lock off" all their start and stop points by hand sewing, rather than run the machine backwards over 3 or 4 stitches..

re the belt ..it may be rubbing against the cut out that it should pass through on the table..adjust as per Wiz's instructions if so..

* approximate way to calculate "how much thread will I use"..measure the total seam length you need to sew, multiply by 7 gives you how much thread ( top and bottom combined ) ..actually that is more than you need , but it will save you running out if you use that as a guide..buy more bobbins, one can never have too many..

Edited August 24, 2016 by mikesc

[robb01]

Thanks, was wondering if there was a rough estimate on amount needed to sew a length. Is there a usual amount that a bobbin sound to 80% holds, ie 30 feet? That way I could figure exactly how many inches I could see per bobbin 

[mikesc]

Depends on the diameter of the thread..( thicker thread means less of it can fit on the bobbin ) and the size of your bobbin ( they are not all the same )..
https://www.superiorthreads.com/education/bobbin-capacity/
http://www.kmkfabrics.com/bobbin_education/
Maybe someone here has figures for the commonly used thread sizes in industrials set up for leather and how much of each one can fit into the various industrial size bobbins ..
Meanwhile the above links may be of some use to you..

Have a look around this link too
http://www.thethreadexchange.com/miva/merchant.mvc?Screen=CTGY&Category_Code=prewound-bobbin-information
and you could try a search using your favourite search engine for.."pre-wound industrial bobbins"
some of the suppliers may well say how much thread is on the bobbin, bear in mind that when you wind your own, you'll probably get between 5% to 10% less on yours, because their machines are set up to just wind bobbins..

Then of course there are the machines which use "shuttles" ..

Edited August 24, 2016 by mikesc

[brmax]

Sounds like a nice setup your working with.

About two knuckles slack when pushing on the centered belt for tightness is all you want, though you want at least 1.

I think it starts to become easier for the threads to be pulled and/or held back at 2:00 when starting about 3 stitches.

After 60yards of seam take a look see ; )

Have a good day with the new machine

Floyd

[CowboyBob]

With #69 thread it's 48 yds,#92 is 35 yds.

[Wizcrafts]

I read the specs for your machine and see that it uses a M style bobbin. My previous National 300N also used that bobbin and here is what I remember from it's thread capacity. With a fully loaded bobbin, of #138 Weaver bonded nylon thread, I was able to sew between 12 to 14, two piece, suede lined rifle slings together (tails and bodies). This was with tightly wound bobbins set to auto-unload at the maximum safe capacity, wound evenly across their internal width. This meant spending a few minutes centering the tension disk on the other end of the bobbin winder. They are almost never set perfectly right from the get-go. When sewing typical dress belts or guitar straps, I would get about 12 per load.

#138 thread has 22 pounds breaking strength and has a bolder than normal appearance, compared to something from China. If you use #69 thread, you should be able to sew twice as many belts or straps. Using #92 will split the difference.

This assumes that the spools of thread are actually the diameter that their "size" actually requires them to be. I find that cross section diameters sometimes vary between brands of thread.

[robb01]

Appreciate all the help. Im guessing more time at the table will help with tis, but im getting some knots showing up when rounding corners, guessing just need to find the right tension? Running 138 in both sides. 

 

First project: Didn't turn out too bad, a lot to learn

 

http://imgur.com/a/huEOT

Edited August 24, 2016 by robb01

[Uwe]

In my experience hauling a top-heavy sewing machine in a trailer is a bad idea. If the machine is not tied down inside the trailer it's a VERY bad idea. You're lucky the whole thing wasn't upside down when you got home after driving two hours.