March 13, 2013

Juki DSC - 246-6

Actually this is one of the 1st machines I bought after many years of making shoes and paying someone else to sew the uppers.

I got it used from a CCS schoolmate in 2009 without stand or motor. 1st I turned it over to Brad for an overhaul and then I made my own stand that fit exactly into a slot between work tables in my shop.

The original DSC was a top of the line machine with auto thread cut-off and power reverse switch. I took off the auto thread cut-off but evetually reinstaled the power reverse, the switch is just a couple inches away from your hand.
The motor and foot control came from my 30 year old Soldner potter's wheel; an outstanding low speed motor and controller.

Tthe DSC is a cylinder arm walking foot machine I have a foot for working on either side of the needle foot. I use this machine for heavy work, not knowing what I was doing when I bought it I thought one needed a walking foot for all types of leather... not so.

I also made this very cool spool holder out of a piece of stainless, I never use the industrial spool hook-ups because they are too large and I would never buy a large cone of thread.

See my other post

March 12, 2013

Sewing machine needle details

I thought I would give a little insight on the Needle! It's so small but has the potential to effect the outcome of your work both positive and negative.

The whole story on needles can be found out there on the net, I am just going to focus on two very important aspects:
  1. The features that make the needle work
  2. The size issue

Thanks to this great section drawing I am able to describe these two inter-related topics.

The bobbin hook is always on the opposite side of the groove in the needle (3) or the groove in the needle faces away from the hook that is spinning or oscillating around the bobbin.

The notch in the needle (4) is the area where the hook passes by the needle to pick up the thread loop. The hook passes by incredibly close to the needle (approximately .002" - .001")

Sequence of events:
When the needle is driven thorough the material the thread is of course held close to the needle, as the needle begins to retract however there is a difference in the amount of drag from front to back. The difference is a result of the front groove. When the needle retracts, the thread on the hook side (4) drags on the material thus forming the loop. The loop is suspended in space and is large enough for the hook to fly by and pick it up, awsome!

So a couple of hard learned lessons regarding this very short time-span event...
  • If the fabric lifts with the needle no loop will be formed and therefore no stitch can be made. I learned this on my wheel feed machine when the leather picked up very slightly and caused no stitch to be formed.
  • Too big of a needle will not allow for the required amount of drag on the hook side and also result in no stitch being formed.
  • If the outer part of the thread is being striped from the thread core you have too small a needle.
Ultimately the correct size needle and thread are required. Needles should be treated as disposable items, don't try to conserve them, just buy more.

Cut - away drawings are so cool:

And now you know how a VW bug works :-)