When I am sewing on my VX-1435 sewing machine, the top thread and the bottom thread do not engage, why?

Threading the Baby Lock BL2400 sewing machine can be done by following these steps:
1. Raise the presser foot: Lift the presser foot lever to raise the presser foot.
2. Thread the upper thread: Take the thread spool and place it on the spool pin at the top of the machine. Follow the numbered threading path indicated on the machine or in the instruction manual. Typically, the thread will go through a series of thread guides, tension discs, and the take-up lever. Make sure the thread is properly seated in each guide and tension disc.
3. Thread the needle: Thread the thread through the needle from front to back. You can use the automatic needle threader if your machine is equipped with one, or manually thread the needle by holding the thread with one hand and passing it through the needle eye.
4. Load the bobbin: Wind a bobbin with the desired thread and place it on the bobbin winder spindle on top of the machine. Follow the specific instructions for your machine model to wind the bobbin correctly. Once the bobbin is wound, place it in the bobbin case and thread the thread through the appropriate guides or tension mechanism, ensuring the thread is properly engaged in the bobbin tension spring.
5. Insert the bobbin: Insert the bobbin case into the machine's bobbin compartment, making sure it is securely in place. Follow the threading path indicated on the machine or in the manual to ensure the bobbin thread is correctly threaded.
6. Bring up the bobbin thread: Hold onto the top thread with your left hand and turn the handwheel toward you with your right hand to lower and raise the needle. As the needle rises, a loop of the bobbin thread will appear above the needle plate. Gently pull the top thread to bring the bobbin thread loop up through the needle plate.
7. Pull both threads to the back: Hold both the top thread and bobbin thread together and gently pull them toward the back of the machine, ensuring they are out of the way of the needle.
8. Perform a test stitch: Once you have threaded the machine, insert a fabric scrap under the presser foot and lower the presser foot lever. Select a straight stitch or another desired stitch on the machine and slowly begin sewing to test the stitching.
Remember to consult your Baby Lock BL2400 instruction manual for specific instructions and diagrams related to threading and operating your particular machine. It will provide you with detailed guidance tailored to your machine's features and functionalities.

OR you can watch the video below

Make sure your presser foot is in the up position before you thread the machine. Dull, bent needles will cause stitching problems, can make the machine work harder, or can damage the machine or your fabric so change the needles often; some say after two medium size projects. Dull needles can make a plucking noise so listen to the noise your machine makes right after you put in a new needle. Make it a habit to listen to the needle noise as you sew also. Dull needles make a "plucking" noise. Check to make sure the top thread is engaged between the two tension disks and that there are no fuzzies in the tension disk or bobbin/ throat plate areas. Make sure the thread and needle are compatable. Refer to your sewing machine manual or find an online chart that references your thread to the proper needle type, size and the proper fabric types that work best. Use the same thread in both top and bobbin. Completely remove your thread and try another thread - top and bottom. 100% polyester thread is some times problematic. Some machines won't sew with certain threads. If nothing worked, you will probably need to adjust the top tension knob. There are some good youtube videos. Look for one with a higher number of views. Loops under the fabric means you need to tighten the top tension (turn knob to right) gradually until you get a proper stitch. Most experienced sewers do not like to adjust the bottom tension screw on the bobbin case if it can be avoided. Bad things can happen if the screw pops out :( !!! I have a friend who sewed all her own clothes in 4-H, high school, college, and many of her children's clothes. After about 40 years of sewing and properly maintaining her machine, I received a call from her because nothing she did worked to get her machine to sew a good stitch. She had no idea there is a bottom tension adjustment on the bobbin case. One last time...do not adjust the bobbin case tension unless you know what you are doing. The screw should never be unscrewed so that it pops out. It will often not go back in correctly. Some some sewing machine repairmen/women can rebuild the bobbin case if the screw is still good. A new authentic bobbin case from the manufacturer can be pricey. One of the most common problems are tension problems. Do not let children or inexperienced adults mess with your knobs. There are youtube vides that address just the bottom bobbin case tension adjustments. If you are working on an important project, write down the type of fabric and thread you are using, stitch length and width settings, and the number setting on your tension knob. Or you can take a picture of it on your phone. This is even more important for sergers. I also record this information for appliqu? stitches, top stitches and quilting stitches (etc.) and keep it with the pattern envelop so if I make the project again, I have a starting place and save time and frustration. I hope this helps you.

Am unable to locate a manual for your machine, although this one may be helpful:

Brother VX 1435 Operation Manual Threading The Machine Winding The Bobbin

Sometimes, similar models operate the same.

Install a brand new needle. Verify that it is threaded properly. If it still will not stitch, the machine has probably been knocked out of time. You can search the internet for web sites & videos regarding sewing machine timing or take it for service.

You can search for a manual:

Make Model manual

or contact manufacturer support.

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You need to check few things:
1. If the needle not bend, the best just to put new needle.
2. Now the needle must bu installed correctly it's very important that it' on the right height and in proper direction so the bottom hook gets into the thread loop after needle moves 1/32" up.
3. If this doesn't help check the bottom hook, it must be smoth and have sharp point if not it might be demeged
and needs to be replaced.
All this must be in the instruction book, just sometimes in very
ocward way.

The needle thread breaks
1. the needle thread is not threaded properly
2. The needle thread tension is to tight
3. The needle is bent or blunt
4. The needle is incorrectly inserted
5. The needle thread & the bobbin thread are not set under the presser foot when starting to sew
6. the threads were not drawn to the rear after sewing
7. The thread is either to heavy or to fine for the needle

do you have a manual for the machine?
try adjusting the top thread tension one number or letter higher
till the stitches look good

change the needle it could have a burr or be damaged
also check the needle plate & bobbin area for burrs

Check the timing of the needle to the hook. Here is a guide to generic principles of Timing
http://www.sewusa.com/Sewing_Machine_Repair/Sewing%20Machine%20Hook%20Timing.htm
Best Wishes Martyn
Bargain Box in Australia

hi! there wind thread on bobbins winder 4 times by your hand rotate clockwise,insert in shaft bobiins winder on top of your machine near hand wheel push latch to engage loop thread on disc winder tension start your machine on pedal foot automatically winder disengage if already filled up of thead pull this winder and insert to bobbins casing insert thread to slot and pull out winder should rotate clockwise as shown.insert on shuttle hook casing and close cover needle plate.next thread your upper

threading tension as shown on red threading from spool pull threading and loop to dial tension threading and insert thread to lever needle and to needle hole tip. pull tread under the needle foot and feeder tooth.rotate hand wheel counter clockwise to hook up thread bobbibs and appear at top of needle plate,teo thread shoul appear,set dial tension to # 3 and stich to # 8 range to # 12 depend on fabric and layer of fabrics and set on straight stich sewing,let needle on upper position insert fabric for trial sewiing.put down foot needle lever. manually by hand rotate for assurance needle is free to sew if obtruction on loop bobbins thread occurs adjust all tension gradually then try again until free from sewing w/o problem star sewing.