Members Dave4 Posted January 1, 2017 Members Report Posted January 1, 2017 The best explanation I can find of check spring function is from the Navy manual: The check spring prevents the needle from stabbing into it's own thread by keeping tension on the thread until the needle tip buries into the material. Just when the needle eye reaches the goods, the check spring should land on it's stop, thereby relieving tension on the thread just as the takeup lever begins its down stroke. If my observations are correct, the check spring should not enter the game again until after the hook has carried the captured upper thread more than half way across the bobbin face on its journey to becoming a lockstitch. Once the thread has crossed the bobbin case face, the check spring should again take a load as the rising takeup lever pulls each knot tight. If the only movement you see in your check spring is smooth up and down sweeps synchronized with the needle and takeup action, it's probably functioning correctly. However, if you see the check spring making little jerking spasms at the start of each takeup lift, what you are seeing is tension loads on the thread at the very moment that the thread is trying to cross the face of the bobbin case. It shouldn't do this. Possible solutions: advance your check spring stop to reduce the range of motion of the check spring so that the thread has time to get past the halfway point of the bobbin case face before the check spring actually picks up any load. Or, slightly advance the hook timing relative to arm shaft timing so that the hook has time to bring the thread more than halfway round the bobbin case face before the takeup lever begins to pull the thread up. Or optimally, adjust both. Check spring range of motion is determined by where you set the stop and by the relative position of the thread guides adjacent to the check assembly. Check spring tension is determined by how much preload you set into the spring according to the adjustment procedure for your machine. Assuming all of the above is correct, I guess I'm finally getting to my own questions. :-) 1 - My understanding is that you only need enough check spring tension to keep slack out of the thread during the check spring duty cycle (about half of every stitch). This means that check spring tension just needs to be pleasantly firm, not snappy taut. Is this correct? What effect does too much check spring preload have? What problems does it cause? Are there any rules of thumb setting check spring tension differently according to thread weight used or thickness of material sewn? 2 - I have recently been playing with check spring settings on a handful of household machines plus a 31-15 and 206RB. If I try to set these machines up so that the check spring lands on the stop when the needle eye hits the goods, and so that the check spring isn't trying to introduce tension before the thread has made it around the bobbin case face, I invariably end up with a stop setting that results in only a tiny range of motion for the check spring. Like a quarter inch total, or maybe 3/8" max. I must have it set in my head that the check spring should moving in a sweeping arc, not a small blip. On rural roads, most oncoming drivers wave as you pass each other. Some lift their whole arm and do a nice big wave. Some barely lift a finger off the wheel (stingy wave). My sewing machines all now have really stingy check spring waves. Is this normal? Quote
Members gottaknow Posted January 2, 2017 Members Report Posted January 2, 2017 Once you get the stop set to ensure the thread is still taught as the needle enters the material, the torsion of the spring should corespond with the needle thread tension. The tighter your needle tension, the more check spring torsion. Sometimes you can find a happy place and it will accommodate different tensions. I don't set my hook timing to make the check spring happy, I set it to compliment the hook timing and thread tension required to make the best stitch possible. I always encourage people to experiment with check spring setting to see the cause and effects. Regards, Eric Quote
Members Dave4 Posted January 2, 2017 Author Members Report Posted January 2, 2017 11 hours ago, gottaknow said: Once you get the stop set to ensure the thread is still taught as the needle enters the material, the torsion of the spring should corespond with the needle thread tension. The tighter your needle tension, the more check spring torsion. Sometimes you can find a happy place and it will accommodate different tensions. Thanks Eric. This gives me a better starting point. Quote
alexitbe Posted October 13, 2017 Report Posted October 13, 2017 So as the needle enters the leather there should be no tension on the thread from the check spring or can it remain until the needle starts its upward cycle? Mine is doing the latter. I am having difficulties with a glove sewing machine... I wasn't until I removed the check-spring assembly to clean... My problem is that the check-spring or something is pulling the leather away from the sewing surface right at the top of the needle cycle as it sets the stitch.. And thus pulling the bottom thread through... I have reduced the check spring torsion to quite low.... Cheers Alex Quote
alexitbe Posted October 13, 2017 Report Posted October 13, 2017 It seem as our own dear Uwe has done a video...Whilst there is no mention of what constitutes too much torque/tension he does clarify the stop position... and that is as it enters the fabric Thanks Uwe! Alex Quote
Members Gregg From Keystone Sewing Posted October 14, 2017 Members Report Posted October 14, 2017 This information at the one minute mark...is impossible to find. The only place I remember reading this is, actually in the 111W manual. None of any of the modern manuals for many machines that use the same tension go into this in the owners or even engineers manuals, yet the thread controller stop is a critical setting. Quote Industrial sewing and cutting, parts sales and service, family owned since 1977, Philadelphia, Pennsylvania USA, 215/922.6900 info@keysew.com www.keysew.com
Moderator Wizcrafts Posted October 14, 2017 Moderator Report Posted October 14, 2017 Not yet mentioned is the purpose of the screw in the little curved slot on the front of the check spring assembly, over the shaft and nut. This lets you fine tune how much slack thread is sent to the bobbin and shuttle; aka: the throw. Turning it all the way clockwise feeds more thread on the downstroke and around the bobbin case. Turning it counterclockwise feeds less thread to the shuttle. If your threads is snapping a bit as the thread goes around the shuttle, try adjusting the throw using the set screw. Quote Posted IMHO, by Wiz My current crop of sewing machines: Cowboy CB4500, Singer 107w3, Singer 139w109, Singer 168G101, Singer 29k71, Singer 31-15, Singer 111w103, Singer 211G156, Adler 30-7 on power stand, Techsew 2700, Fortuna power skiver and a Pfaff 4 thread 2 needle serger.
Members dikman Posted October 14, 2017 Members Report Posted October 14, 2017 Thanks Wiz, I had been curious about that screw. Quote Machines wot I have - Singer 51W59; Singer 331K4; Seiko STH-8BLD; Pfaff 335; CB4500. Chinese shoe patcher; Singer 201K (old hand crank)
alexitbe Posted October 15, 2017 Report Posted October 15, 2017 13 hours ago, Wizcrafts said: Not yet mentioned is the purpose of the screw in the little curved slot on the front of the check spring assembly, over the shaft and nut. This lets you fine tune how much slack thread is sent to the bobbin and shuttle; aka: the throw. Turning it all the way clockwise feeds more thread on the downstroke and around the bobbin case. Turning it counterclockwise feeds less thread to the shuttle. If your threads is snapping a bit as the thread goes around the shuttle, try adjusting the throw using the set screw. Wizcraft, is that screw P or Q on the figure shown above? Is it finely adjusting the position of the spring stop? Thanks Alex Quote
Members Constabulary Posted October 15, 2017 Members Report Posted October 15, 2017 I think Wiz means #25 in the below picture Quote ~ Keep "OLD CAST IRON" alive - it´s worth it ~ Machines in use: - Singer 111G156 - Singer 307G2 - Singer 29K71 - Singer 212G141 - Singer 45D91 - Singer 132K6 - Singer 108W20 - Singer 51WSV2 - Singer 143W2
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