29K Timing

[Ole South]

I know this has been a topic ad nauseam, but I've run into a unit with problems. I've dealt with most issues but still stuck with skipped stitches.

It's a Sewline model SL29 the owner purchased off eBay. Unit has never worked properly since owner purchased it. Three industrial sewing machine mechanics have worked on it before me (I am not a sew tech).

Here is the timing:

The needle descends and then rises about 1/16",

the hook barely catches the very top of the scarf and then proceeds around as the needle descends again and pauses.

The needle rises setting the loop and begins the next stitch.

When I set the timing that the hook passes the scarf just above the eye... the rack and driver pinion gear run out of teeth and bind, hard stop. At the current setting the machine stitches about 5-6 good then skips 1 or 2, rinse and repeat.

I can't rotate the pinion gear on the shuttle shaft as it is a "through the shaft" set screw.

The machine is EXTREMELY picky about hook and bobbin selection!!!

Here's my question:

Should the hook pass the scarf on the first needle rise or the final needle ascent? I know it needs to pass nearer the eye but knowing which part of the cycle changes where to make the timing adjustment. I haven't run into this problem on other Singers but my 29-4 doesn't have that descend/rise/descend needle motion and I don't have easy access to a true 29k-71 for reference. And yes... both ascents and descents are machined into the cam follower pulley.

Some of the other problems I've found:

1. The rack drive toggle connector knuckle was impacting the casting at the end of the throw, I've ground a bit from the casting allowing the driver rod full motion. This allows the timing to remain constant even if it seems incorrect.

2. Voids in the cam follower pulley race that appear to bind when sewing a single layer 4-5oz veg tan.

3. Burrs throughout the entire thread path.

4. Gouges in the shuttle drive pinion gear's bearing surface (poor factory machining), This may also be a factor affecting the binding in #2.

The owner is stuck as they can't afford to purchase a new patcher and can't afford not to have one onsite. Any help would be most appreciated.

Thanks

[Constabulary]

I read what you write and I have a 29K71 but seems there is something different going on with this SL29 machine. I would assume the cams are poorly manufactured and the gears and rods too. In this case I think I have to have this machine in front of me and try it out by my self.

Just an assumption - has your gear box two small squared looking holes on the tip of the gear box where the tips of the rod comes through? I ask because I assume the rods are too short and Chinese probably have produced a gear box w/o the opening for the rods and that why the have used shorter rods but since I have no pictures I can´t tell. This is just a very wild guess since I never have seen a Chinese patcher...

Edited February 23, 2016 by Constabulary

[Ole South]

Thanks Constab,

The pinion gear is definitely running out of teeth. Yes it does have the openings for the racks to exit the end of the horn.

Does your 71 needle rise twice each shuttle cycle?

Edited February 23, 2016 by Ole South

[CowboyBob]

Steve,

The shuttle should catch the thread on the first rise of the needle.

[Constabulary]

Yes, that's how the thread loop is formed the hook tip is catching. It is making a small jump before it raising again. All 29K patchers (and others) are doing this.

Have you checked a 29K71 manual and have compared the number of teeth of the racks? There is picture showing the open gearbox. It also explains the timing but not sure if it helps in your case. Your machine has a timing eccentric, right?

[SARK9]

I recently bought a Consew 29B and it had some similar (though minor) hiccups....but on the whole, its overall build quality really isn't that bad. The Consew seemed to be a bit too fussy about its bobbins and tensions at first, and I finally replaced the original shuttle with a good quality Japanese aftermarket unit and it made a world of difference....all tension problems evaporated. Mine is a large bobbin machine however, so it may be apples and oranges here.

The main flaw mine had which occasionally caused the odd skipped stitch was; The machined area on the needle bar which accepts the *thread tension spring* was either milled a tad too short, or the furnished spring is a few thou too long...so the working tip would occasionally bind in its recess and not apply any tension at all to the thread. I very slightly re-arched it and it is able to move freely now. Any issues with that little flat spring seem to bring skipped stitches.

-DC

[Ole South]

Thanks to all of you folk!! What a life-line this crew is!!! The whole not hitting the scarf bothered me all day so once Bob and Constab verified the timing was right all that was left was needle bar height... and of course we can't adjust that readily so.....

Thinking outside the box... I swapped out the 135-17 needle for a 134-35 from my Adler and viola!!! IT STITCHED 18" without a single skip and this was with a crappy hook!!! *happy dance* still have some tension issues to work on but this is great for the owner.

The 134 needle is a few thousandths shorter than the 135 thus raising the scarf and that minute variation made a huge difference in the final product.