Singer 66 straight stitch examples
 

It is a 66-1 from 1911, I have put in the original back clamp presser bar and forward only stitch regulator. This seems to make the machine happier. I may put in the side clamp bar just to see how well it'll stitch but right now for short bursts it's doing well. So I'm thinking I'm also the problem. If the fabric isn't sitting under the needle fairly square it seems to glide away at a curve. The short piece of double layer fabric has the first two lines from the top using a fabric guide. Each successive line is just the machine running on its own, no guide

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You see some have a slight curve and return. What am I doing?


Ps: I'm also an unseasoned sewer so the fabric not sitting square or other user error is on my own head :)

With model 66, like most of the narrow footed straight stitchers, it's very easy to guide the fabric for perfectly straight seams, and both curvy and angular turns are done with ease. This is one of their advatages and it makes them a joy to work on. You do have to guide the fabric with you hand every so slighly and you can't sew completely "hands free". Your test stitching looks good though. If you have checked the feed dogs and made sure they move in a straight line 180 degrees on the fabric it's adjusted fine. Do the test with a ruler if needed. Also make sure the teeth lay flat, as close it gets to a perfectly horizontal plain. Do this by eye, and the check with a flat ruler on all four sides (or flat piece of other material ). The natural movement of the feed dogs is cirular, as I'm sure you already have figured out. Feed dogs can in theory be worn or damaged, but usually not, even on machines that have seen a lot of use they are tend to be all fine. It's worth checking the state of the teeth.

Don't give up on fine tuning your machine, if you have messed a lot with it, it might need a "full service". Here is a link to a simple service manual. If a part isn't obviously out of sync I wouldn't fiddle with it. I don't know what condition your machine was in when you got it, but usually they get better after a period of regular use and maintanance (extra tentatively and frequently oiled and cleaned for a period). The advice can seem a bit over the top, but if there were signs of rust or lots of grime, it will take a bit for it all to be flushed out. Rust will gradually dissolve as the machine is used, depeding on what type of oil and fluids you have cleaned with. The oiling part is repeated ad nauseam, but it's almost impossible to be to tentative in a run-in period.

Model 66 does perfect stitches, it's a nice model. I think you might have ever so slight tension imbalance on the stitching test. When balanced the stiches should form a perfect line of arrow straight stitches. I'm being very fuzzy now, but when you have the interlocking of upper and lower thread happening in the two pieces of fabric, they will hardly show. You are doing all correct, test sewing with two layers of light cotton.

Aren't the teeth sort of set at a 45 degree angle? They seem to be angled.... what do you mean by lie flat on a horizontal plain? Not sure what part should be horizontal..

The feed-dogs should be the same height (horizontal plane) above the needle plate - front and back, left and right. This has nothing to do with the angle of the teeth themselves.

I'm with you all the way in your quest for perfect alignment. I just refurbished a 66k myself, and have similar worries about not getting the final touches, especially the transport, right. However, after some real sewing with the machine I'm more willing to classify them as "test patch problems" not really interfering with normal operation.
As has been mentioned, with flatbed, straight stitch machines material is easily guided and turned due to narrow feed dogs. This will also limit their ability to transport material straight over distance. The slightest drag on one side will pivot it and change direction. In real sewing, where most of the time there is more material on the left side, there will be more drag. Either way, active guiding is usually necessary.
I just try to talk myself away from letting perfect get in the way of good.

Stay addicted, Stein

I am not so sure you have a problem, it may just be you aren't used to using it just yet. Your stitching looks pretty good to me. I am a picky sewist too, however my seams aren't as straight as they used to be, must be getting old and more blind or some other good excuse.lol

You could sew on some lined notebook paper and see while guiding it slightly if it is doing something wrong.

Glasses, good light, and the usual mantra of oiling lol. I need glasses or contact leses to see sharp edges and correct any blurriness.