IngleGunLeather Report post Posted August 27, 2012 Hello everyone. Well, I need a little help with some fine tuning in order to move forward with a western holster with a welt. outer leather: 6/7 oz HO liner leather: 6/7 oz HO welt leather: 2x 6/7 oz HO skived down to taper needle: 23 thread: 207 bonded nylon machine: Cobra Class 4 When I sewed the liner to the holster I was getting consitant stitching at 6 SPI When I went to sew the seam together, well, it turned out nasty. No changes were made from sewing in liner to sewing the seam with welt. I'm sure I need to make a change, but not sure what I need to do. That's where I need your help. Please see pics below. Toe end of seam (equal to four 6/7 oz layers) Trigger guard transition (going from four 6/7 oz to six 6/7 oz layers) Upper trigger guard (full thickness of welt is six 6/7 oz layers) notice the difference in the stitch lengths? Quote Share this post Link to post Share on other sites
acowboy Report post Posted August 27, 2012 you have to adjust your stitch length for the thicker leather....the stitch length shortens as you sew thicker on any machine...practice will teach you...on my adler i just give the knob 2 or 3 clicks and keep drivin.... Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted August 27, 2012 The shorter stitches happen due to the pendulum effect of the needle bar pivoting from the top. Only a square drive (e.g. Union Lockstitch, Campbell-Randall, or Luberto Classic) machine maintains semi-constant stitch length over wide changes in thickness. Even my Union Lockstitch has a slight variance in thick leather, if I am using a size 2.5 or smaller needle. The dang needle flexes under heavy loads, even though the parts moving it are on a square path. Quote Share this post Link to post Share on other sites
Go2Tex Report post Posted August 27, 2012 Yeah, one of the most frustrating things about machine stitching. I try to avoid the uphill situation for that reason, but it's almost impossible on some things. Once I have the length set up, it's a pain getting is back if I change it. So, when you know you are coming to a thicker area, help it along a bit until you get up onto the level again and your stitch length should equal out. Or, like with your welt with the taper, don't use the motor. Use the flywheel to hand turn it and make sure the needle is in the right location to keep your stitch length the same as the rest. I hadn't considered the cause being the pendulum effect. I just thought it was slipping, but the needle actually bending probably explains why sometimes needles get nicked and burred on the plate. Quote Share this post Link to post Share on other sites
IngleGunLeather Report post Posted August 27, 2012 Yeah, one of the most frustrating things about machine stitching. I try to avoid the uphill situation for that reason, but it's almost impossible on some things. Once I have the length set up, it's a pain getting is back if I change it. So, when you know you are coming to a thicker area, help it along a bit until you get up onto the level again and your stitch length should equal out. Or, like with your welt with the taper, don't use the motor. Use the flywheel to hand turn it and make sure the needle is in the right location to keep your stitch length the same as the rest. I hadn't considered the cause being the pendulum effect. I just thought it was slipping, but the needle actually bending probably explains why sometimes needles get nicked and burred on the plate. I didn't think of hand cranking it through and placing the needle at equal lengths. I could use an over stitch tool for marking the spacing. Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted August 27, 2012 The pendulum effect is not just the needle bending. It also involves physics. There is more travel at the bottom than towards the top of a swinging pendulum. Thus, the needle swings longer at any stitch length setting at the flat throat plate level than 1/2 inch above it. A 12 ounce holster perimeter will have longer stitches than a 32 ounce side rib, unless you change the stitch lever setting. All common sewing machines use the pendulum needle bar system. However, there are a few non-standard machines available that have true square drive for the needle bar. These machines push and pull the needle bar along a straight horizontal line. My Union Lockstitch is such a machine. The Luberto Classic, based on the Number 9 machine is another. All of the Randall stitchers have square drive. I suppose the Landis 3 does also, but can't say for sure. Quote Share this post Link to post Share on other sites
TwinOaks Report post Posted August 27, 2012 Do most of the needle and awl machines keep a constant stitch length? If so, I might reconsider getting rid of the Champion (rebuild project). Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted August 28, 2012 Do most of the needle and awl machines keep a constant stitch length? If so, I might reconsider getting rid of the Champion (rebuild project). Basically, yes. However, a thin needle moving thick leather can bend or be held back slightly by the load. The mechanism would have to be very tight to avoid any change in stitch length over a large change in thickness. Quote Share this post Link to post Share on other sites
