Singer 306K/320K Using standard needles – With Pictures

I have previously written about converting the bobbin cases of Singer 306K and other swing needle Singers in my post      ……  to enable standard (15X1) needles to be used in these machines.  (They were designed to use an alternative, shorter needle than is standard).

I have also discussed the possibility of obtaining alternative bobbin cases for these machines, thus obviating the need for any modifications at all.  This can be viewed at

There seems to be some confusion regarding the issue of needle strike, when using standard (15X1) needles.  One concern that has been raised is the possibility of the longer needles penetrating and catching in the bobbin thread.  Another is needle strike that occurs on other parts of the bobbin case.  I will attempt to clarify these remaining matters below.

The first photograph shows a Singer Model 306K with a standard (15X1) needle fitted.  The needle is at the central position and is at full descent.  BEHIND the needle, can be seen the bobbin from which the lower thread is supplied.  Please note that the needle descends BESIDE the bobbin.  In normal circumstances, there is no possibility whatever of the needle coming into contact with the thread that is stored on the bobbin.DSCF0841 These next two images show the needle at full descent and at the extreme right and left positions i.e. the extreme positions encountered when using zig zag stitch at maximum stitch width.  The two points to be noted here are that there is again no danger of the needle making contact with the thread stored on the bobbin and also that there is ample clearance between the needle tip and the bobbin case itself.  This particular bobbin case has been modified, as discussed in the article referred to earlier.DSCF0857 DSCF0858

And finally, this last photo shows a bobbin case with obvious needle strike damage of the kind often blamed on use of standard needles.djaggjjgThe area of the bobbin case that would be struck by a needle that was too long is the thick metal at the bottom of this photo (the area with the two slightly diagonal scratches).  This is the part of the bobbin case which I modify by grinding away some metal to increase the clearance space for the longer standard needle.    The significant damage to the shroud is obviously caused by repeated needle strikes but this (in my opinion) has nothing whatever to do with the length of the needle used, and everything to do with what, in the IT industry, would be referred to as a 1d10t error, on the part of the operator.

So given the first three photos, showing that the machine’s needle descends BESIDE the bobbin, how is it possible for the needle to impact a part of the bobbin case that isn’t within a bull’s roar of the needle’s normal operating area?  This is indeed the area where the needle (long or short) would possibly descend into and foul in the bobbin thread, if it hadn’t instead struck the shroud.  The shroud is what covers most of the bobbin and, in the case of this particular bobbin case, there appears to be a gap that would expose part of the bobbin and its thread.

There are only two ways that I can think of, that would enable a needle of whatever length to contact these areas.  One is if the bobbin case is not FIRMLY AND CORRECTLY set on its spindle and properly locked into place.  The bobbin case has a locking bar which must engage a groove of the end of the spindle.  If it is not properly locked into place, it will begin to slide off the spindle with normal operation and ….. surprise, surprise …. that evil needle (which is still going up and down in the only position that it can) will attack the bobbin case viciously …. as the injuries to this one attest.

The only other possibility that I can see, is if the needle is severely flexed out of its normal position … and I do mean severely.  The only way this is likely to occur is if the operator is fighting against the operation of the feed dogs and trying to force the fabric through the machine much faster than the feed dogs would.  (I have seen much damage to needle plates which is also caused by this and which has likewise been blamed on the use of the wrong needles.)  Alternatively, if the operator tries to force the machine to sew an absurdly thick wad of fabric, I imagine that the feed dogs themselves might force the needle to be flexed in such a way.  I stress that this latter suggestion is pure speculation on my part.

Any way that I look at this issue, I am unable to arrive at any conclusion other than that these very fine machines which are capable of so much fine sewing and an impressive array of stitches are nevertheless very vulnerable to 1D10T errors!

They are, at the end of the day, a domestic sewing machine, designed to sew up some clothing for the family, perhaps an occasional curtain.  They aren’t meant for sewing tarps for semi-trailers or for making horse blankets.  They do what they were designed to do very well and, given thoughtful use and appropriate care, they will keep on doing it indefinitely.

Modifying the bobbin case or obtaining an alternative one, either of which will enable the use of standard needles, is a simple strategy for extending the versatility and the life expectancy of these amazing swing needle Singers.  If, after making the necessary changes, you are still encountering needle strikes in strange ways …. look for that 1D10T.

I am aware that some people have advocated modifying these machines by altering the height of the needle bar and then (presumably) modifying the hook timing and feed dog timing to suit.  Whether this is genuinely able to achieve the ability to use standard needles and without effecting stitch quality, I am not qualified to say.  But my question would be, why go down such a complicated road with a doubtful destination when there is such a simple solution readily available?

I hope this additional information will be of some benefit to those who might be presented with an opportunity to own a swing needle Singer.  I have several and I honestly do think they deserve a special place in Singer history.

P.S.  Lee Copp of Florida, U.S.A. has written an excellent article regarding use of standard 15X1 needles in a Singer 319W.  You can read his views (pretty much echoing my own) at:

Andrew Caddle  2014-12-28


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2 thoughts on “Singer 306K/320K Using standard needles – With Pictures

  1. Hello Andrew. Thank you for posting the articles in relation to Singer 320k. I have recently taken possession of a 1959 model, which I have now got running well after a lot of cleaning, degreasing and oiling. I have managed to get some appropriate needles for the time being but I will at some stage make a bobbin case modification as you have done. I will get a new bobbin case before attempting the mod. Thank you for your detailed posting.

    • Hi William, Thank you for your comment. Just a couple of thoughts for you, before you go incurring extra expense. Have you examined carefully, the bobbin case that is currently in your machine? Do you KNOW that it isn’t suitable? I have just grabbed the bobbin case out of my own 320K and it is an original Singer part # 173058. I can see that it has been modified, using the grinding technique that I’ve talked about in my article. However, it is possible to purchase a new bobbin case of the same number that is manufactured to the specifications necessary to enable the use of 15X1 needles. Have a look at I would point out that this seller doesn’t ship overseas anymore but I am certain there must be local suppliers from whom you could purchase this (modified design) item. Also, are you sure that your existing bobbin case is unsuitable or that it hasn’t already been modified? (this modification is not a new idea and has been happening for a long time). The simple way to check is to un-thread your machine, install a 15X1 needle, set the machine to straight stitch centre position, open the bobbin case door and observe the bobbin case area, as you turn the balance wheel by hand. You will see the needle point descend into the bobbin case area, just beside the bobbin. Check the clearance when the needle reaches its lowest point of descent. If there is adequate clearance (1 1/2 – 2 mm) try setting the machine to maximum left and right needle positions and observe the needle clearance through several complete revolutions of the balance wheel.

      If the clearance is adequate, it means that either you already have the modified bobbin case design or that your original bobbin case has already been modified. If there isn’t sufficient clearance at the extreme left and right needle positions, then you will need to either have your existing bobbin case modified, or obtain one of these alternative 173058’s. Personally, I’d be looking for the new, modified design bobbin case. Hope this info is of some help. I do like the early swing needle Singers very much and I think its a dreadful shame that there are seemingly knowledgeable people spreading misinformation that will cause people to be put off buying or retaining these great machines. They DO work perfectly well using standard (15X1) needles, when an appropriate bobbin case is installed. If I can be of any further help, please don’t hesitate to get in touch. Kind regards, Andrew.

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