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Thread tension adjustment Singer Slant-o-matic Model 500A

The tension adjustment for the thread from the spool, (not the bobbin) on a Singer Slant-o-matic Model 500A is way too tight.
I had a new spring put on but it still is too tight. I have taken it apart, but haven't been able to figure out how to ease the tension enough. A schematic of how it should look would be great.

Is the repair manual still available?

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  • prutherford1 Feb 08, 2010

    I did not make my self clear, apparently.

    I have taken the entire tension mechanism apart.

    I know very well what good tension looks like when it is working right.

    I have used the machine for a few years.

    I know very well how to thread the machine per the diagraham on the machine.

    Do you know how to reassemble the thread tensioning device with its plates, springs, and washers?

    That is mystery I need to solve....and why a schematic would be nice if available.

    Thanks for your initial reply.



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Loosen sewing thread tension by turning the machine's tension adjustment knob counter clockwise. All though the thread tension may already be too loose, back the sewing thread tension knob out. Be careful not to turn the knob accidentally so much that it falls out of the machine. Check the sewing machine thread from the spool to the sewing needle to make sure the sewing machine thread routes are correct through all of the machine's guides.
Now get a piece of scrap or test material about two feet in length. Place the material under the sewing needle the same way as in a normal sewing process.
In the second step below, look for, while sewing, if a slight noticeable pull to the left occurs as the material passes the sewing needle. When a slight noticeable pull to the left occurs, the machine tension is at proper adjustment. Do not tighten the machine's thread tension knob any further, to prevent any harm to the machine.
Now to begin the second step, turn the machine's tension adjustment knob, one quarter of a turn clockwise. This will tighten the sewing thread tension. Now sew approximately a dozen stitches through the material.
As the material passes the sewing needle, watch to see if the material has a slight noticeable pull to the left. No slight noticeable pull to the left suggests improper sewing thread tension. Turn the sewing machine tension adjustment knob one quarter of a turn clockwise again, to tighten the sewing thread tension, and then sew another dozen stitches.
Keep repeating the process of quarter turn increments clockwise with the sewing machine's tension adjustment knob. Then sewing a dozen stitches, until a slight noticeable pull to the left occurs as the material passes the sewing needle. Once the material does this, the sewing machine thread tension has reached proper adjustment.

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Posted on Feb 08, 2010

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I have dismantled the thread adjuster. can someone help me to put them back in the correct order please.

Posted on Jul 21, 2013


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How do you adjust the bobbin


Set the tension on the sewing machine for the weight of the material you want to sew. The tension setting shows in the stitch on the material. Use the chart on the machine that matches types of stitches with suggested material tensions. An example of this is, the stitch to sew jean material is different than the stitch to sew silk.

Take the bobbin and wind the thread around it. Make sure the bobbin is empty and don't fill it too full of thread. A bobbin filled too full won't stay tightly spun.

Thread the string evenly on the bobbin. Move the thread back and forth evenly and in layers that are level. Many Singer sewing machines have a bobbin winder on the top of the sewing machine, and the consistency of how it threads can save you frustration later.

Find the hole on the bobbin that is located near the inside spindle of the bobbin. Take the thread sitting on the sewing machines spool and insert the thread in the hole from inside the bobbin to the outside. Set the threaded bobbin on the spool designated for spinning on the top of the sewing machine for some Singers.

Turn the side drive wheel slowly until the threaded bobbin has a layer or two of thread on it. Push down on the drive peddle and fill the bobbin, but don't thread it to the very edge. If the bobbin is too full the thread will release erratically. Cut the thread from the spool.

Drop the bobbin into the bobbin case under the area where the needle sews the material. Close the case and turn by hand the side wheel drive until the bobbin threads into the sewing machine. You can tell when the bobbin is threaded by the tiny piece of thread that juts out of the bobbin case where the needle goes up and down.

Grab the thread with your fingers and pull it out approximately 4 inches. Your bobbin is now spun and threaded.

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