Lara,
I forgot to mention that on both of those machines the needle goes in flat to the back, and is threaded front to rear.
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THREAD: Most of these vintage machines such as Lara's 834 and 410 and irishrose's 15 clone were made when size 50 or 50wt ( I've seen it labeled both ways ) was the most common thread. I have instructions from several Singers and some Japanese machines that specify setting and adjusting the tension with this thread. So I've been grabbing every spool of 50 wt thread I can find. It may not be suitable any more to sew with, but it is perfect to set the tensions on these old(er) machines.
I've found that once set with the original 50wt thread they will work well with the newer stuff ... generally.
Joe