a friend and i went together and bought a grace 2 with a janome 1600p. it was used but like new and the only real problem we've had is the thread breaking .have used 50wt egypt cotton and cotton covered poly, also maxilock. tried 14 & 16 needles. does anyone have a suggestion?thanks for any help.our group makes quilts and gives thm to people that are ill and vets, so the quilter is really needed djw

check the tension, if you have changed needles etc, usually the tension is to tight, but a different brand of needle and or thread can be checked, also check for nicks, in the plates and other area, it is it getting caught it could be the issue

I had difficulty when i first started and it turned out to be that the thread I was using (40 wt cotton) was just too soft for the speed I was "driving." If I slowed down the machine to a snail's pace, it worked. But, I didn't want to take months for that project. I switched to a thinner thread that had a bit of poly in it and we sailed! I still have trouble whenever I put in a high end cotton thread. I guess I just need a thread that matches my sewing style.
If the thread is breaking and the tension is ok:
Check the needle - for burrs, and for size and for eye size
Check the spool - try a different one, it may just be a 'bad' batch.
Check that you've rethreaded the machine from top to bottom with the tension discs OPEN. (pressor foot up)
Change to a different type thread
Try changing the speed - if you're pedal to the metal, aim for med - high.
Oh, and make sure the thread isn't getting snagged up. I can't tell you how many times I've broken thread because I folded down my upright spool pin and tucked in the spool for travel, then restarted sewing without replacing the spool on the post! (oops)

I have one of these machines, and I had that problem. OMG!!!! I was going absolutely nuts!! turns out I was trying to quilt over denim with a needle that was to small. Once I got that right. I didn't have the problem again. Can also be how the needle is in there. Do you have the manual that came with it?

yes we have the manual but says nothing about the problem we are having djw

I know. But there is should be something in there showing you how the needle should be in the machine. Its a peculiar machine.lol thats why I was asking.

The Janome 1600p, only one way to put the needle in. The needles have one flat side so won't go in unless you have the flat side where it should be.
If you have your thread though all three holes in the pre-tension guide, try just two hole, it it still breaks, just put it through one hole.
Another thing is make sure you get the thread in the last guide before threading the needle....that was the hardest one for me to get. The manual exlains that and has a diagram, but it was still hard for me to do.