31-15 timing

[sandmanred]

I've had to reset my needle bar to get the hook timing right.  Are there any other adjustments I should look at to maintain good timing of the hook and needle or any other critical motions?

[sandmanred]

Here's a bit more of what's going on.  My 31-5 will occasionally (one start in twenty?) break the top thread on the first stitch.  Once under way it sews fine, hammers through most anything and never drops a stitch.  I'm running a T135 thread with a #23 needle on approximately 12 oz/yd canvas making a pair of jeans type pants.  Same thread top and bottom.  Tension is not maxed out but towards the upper end.  My hook timing is okay I think but the hook is a little sloppy in the race so I ordered a new one but I'm not sure I'm on the right track.  Any other things for me to check out?

[Wizcrafts]

2 hours ago, sandmanred said:

I'm running a T135 thread with a #23 needle

You have exceeded the specified thread size on an ancient tailoring machine that was meant for thin thread. Mine maxes out with #69 thread and a #18 needle. Others are able to run up to #92 with a #19 or #20 needle. Very few machine hackers are able to run #138 thread in a 31-15. It depends on the type of hook you have and how it is adjusted for clearance.

[DonInReno]

These are great old machines - sounds like you have a fun project.

When you are starting a line of stitching do you hold the thread ends tight for a few stitches?  Loose ends can cause exactly what you’re experiencing.   I would be surprised if a new hook will fix the first-stich-goof.  Replacement hooks may or may not be as good a quality as what you have now.

The thread tension should be adjusted so the knot between top and bottom meets in the middle of the material -  if it’s well centered but too tight then both top and bottom tension will need to be decreased.   If the machine was set up for thinner thread, using 138 in it is likely to create too much tension.

Edit:   This manual describes all the adjustments of your machine, but it’s such a simple design very little typically needs adjustment other than the needle bar height.

.    https://www.militarynewbie.com/wp-content/uploads/2013/11/NAVEDTRA-14217-Aircrew-Survival-Equipmentman-1-C.pdf

Edited December 1, 2020 by DonInReno

[sandmanred]

Thanks Wizcrafts and DonInReno,

Yes, I have learned the hard way that holding the threads back at the start is necessary, I usually just pinch them to the table with my thumb.  If I don't I occasionally get 4-6 stitches with loose loops on the bottom side and occasionally a tangled mess.  I thought maybe my current issue is due to starting the stitch with the take up arm too low ( I think it's best to start and stop with it at the top of stroke?) but I debunked that theory as the sole cause of the breakage with a few trials this morning.

I'm maybe a little low with my needle height based on the manual attached above so I'll give that a tweak.

What is the proper shape for the tip of the hook?  Should it feel sharp or rather be slightly rounded?  

FWIW I have had some success running 207 thread on this machine on vinyl, the worst part is you can only get about 15 feet of thread on the bobbin.  

 

[Wizcrafts]

2 hours ago, sandmanred said:

What is the proper shape for the tip of the hook?  Should it feel sharp or rather be slightly rounded? 

The hook should be sharp, pointed and polished.

[sandmanred]

50 minutes ago, Wizcrafts said:

The hook should be sharp, pointed and polished.

Great!  That's the condition and all the edges have a small radius and are polished too.

I adjusted the needle bar to get to the hook timing to the spec in the guide.  It's too early to tell for sure if it's helped but I just got done adding the belt loops.  I use a short stitch and have to go through a lot of layers and often have trouble with a few loose stitches but breezed through all them without a hitch.

 

[sandmanred]

So I did adjust the needle bar to the put the hook 1/16 inch above the eye.  I've had no breakage at start since but it's a little early to declare victory.

[sandmanred]

Also received and installed a new hook today.  The old one is on the left, new one on the right.  Not sure if the shape difference is due to wear or bad copying but I think the longer point will open the loop easier?  

I also find I have to shorten the part on the blunt end of the hook to get enough clearance for the needle thread to pass between the hook and the hook driver, is it normal to have to trim the blunt end a bit when you install a new hook?

 

 

 

[DonInReno]

The new hook looks much better than the old one!    Hooks get rounded over when they run into broken needles.

It would be nice if the aftermarket parts were made to original specifications, but parts today often need a little adjustment to work properly, so what you had to do doesn’t surprise me.  It also might be that it was designed for lighter thread than what you are using, buts great if you’ve got it sewing ok.

I’d hold onto the old one until the new one proves to be reliable.   Sometimes a replacement hook is just not shaped right and will cause you fits.

I’m far from a historian on everything about the 31-15, but there does seem to be a real difference between machines and some will just not sew thread as heavy as 138, but others will.   When I hear someone has a 31-15 it’s been interesting to see what it will sew - it seems older machines prior to the 1940s are less likely to sew thicker thread.   Up until the 1940s there was an almost identical machine, the 31-20, that had a slightly different bobbin and hook designed to sew up to 138 thread.   31-15s can easily be retrofitted with 31-20 parts and visa versa.

In a WW2-era parts manual there was reference that the 31-15 could use a needle up to 23, which would only be required for thicker thread.   It seems likely, at least to me, that a slight change in the hook, and maybe race, was made when the 31-20 was discontinued, even though the part numbers for 31-15 hooks and races didn’t change.

Thats about all I know about ‘em.  
 

 

 

 

 

 

[Wizcrafts]

I have tried and tried, but the thickest thread my 1920s 31-15 can handle is #69, using a #18 needle. My hook is pinned to the shaft and can't even be timed to the needle, aside from bending the shuttle driver tabs, or moving the needle bar. Considering what I bought it to sew (trouser cuffs and wallet interiors), that is just fine. I have plenty of other machines that can use #138 thread and up.

[sandmanred]

Wizcrafts and DoInReno,  thanks for your insights on this topic, I really appreciate you taking the to read and respond.