Andrew Chee Report post Posted March 7, 2012 Hello all, in following this forum I've sometime come across folks that mention something along the lines of using a 207 top thread but a 138 bottom thread. In all the sewing that I've done so far, I've used the same size thread top and bottom. What is the reason for using a different sized top and bottom thread? Is there some practical, functional, or aesthetic reason why this is desirable? I've seen it mentioned a few times and I was wondering why one would choose to do this instead of using the same size thread top and bottom. Thanks. Andrew Quote Share this post Link to post Share on other sites
Techsew Ron Report post Posted March 7, 2012 (edited) Hi Andrew, this is mainly done for tension balancing. By using one size smaller on the bobbin, your machine can more easily pull up the lower thread through the material to have an even top and bottom stitch. Additionally you can fit more thread on the bobbin if it's a thinner thread. Do some experimenting and see if you notice a difference! Ron Edited March 7, 2012 by Ronnie Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted March 7, 2012 Hello all, in following this forum I've sometime come across folks that mention something along the lines of using a 207 top thread but a 138 bottom thread. In all the sewing that I've done so far, I've used the same size thread top and bottom. What is the reason for using a different sized top and bottom thread? Is there some practical, functional, or aesthetic reason why this is desirable? I've seen it mentioned a few times and I was wondering why one would choose to do this instead of using the same size thread top and bottom. Thanks. Andrew Don't do this if you are sewing holsters meant for official duty use or competition shooters. The smaller thread becomes the weakest link in the package. In a life or death struggle for a gun in a holster, the weaker threads could give way. Quote Share this post Link to post Share on other sites
Andrew Chee Report post Posted March 7, 2012 Hi Andrew, this is mainly done for tension balancing. By using one size smaller on the bobbin, your machine can more easily pull up the lower thread through the material to have an even top and bottom stitch. Additionally you can fit more thread on the bobbin if it's a thinner thread. Do some experimenting and see if you notice a difference! Ron Thanks for the replies. I guess this is not necessary unless I get into a situation where I'm having a hard time getting enough top tension then? I will keep that in mind if the situation arrises. Thanks for the help. Andrew Quote Share this post Link to post Share on other sites
Cobra Steve Report post Posted March 7, 2012 (edited) Hi Andrew. The rule of thumb as I learned it, is, whenever using a 346 thread on top, you must use a 277 in the bobbin. This is because of the reverse stitch. In each hole that the needle punches, there are 4 strands of thread and 1 knot, but when you sew in reverse in the same holes, then you are doubling the amount of thread and knots, now there are 8 strands of thread and 2 knots in that hole. There is not enough room in those holes for all that thread and 2 knots so the thread tends to lay at the bottom and doesn't pull up into the leather. The end result is not a clean back tack. This rule only applies when using a 346 thread on top. If you are using any other thread size, you can use the same size in the bobbin. Many people use a lighter thread in the bobbin because (as Ronnie said), you will get more yield on the bobbin. I only mentioned 346 thread because 415 thread is rarely used any more. Thanks, Steve Edited March 7, 2012 by Cobra Steve Quote Share this post Link to post Share on other sites
Kevin Report post Posted March 8, 2012 I believe on the old needle and awl machines, this was recommended in the owner's manual to get a tight stitch. Kevin Quote Share this post Link to post Share on other sites
