My stitch is stuck on a small stitch and I can't make it bigger. Is my timing slightly out?

It may be as simple as the dial is set to buttonholes which makes a short stitch and the zig zag would be small.

If this has occurred following service, take it back. They need to check it again.

...

Not much information to go on. What do you mean it won't sew a straight stitch. It just won't sew a straight line? It won't form a stitch? What?

Skipped stitches

1. The needle is not inserted correctly

Remove needle & reinsert needle( flat side towards the back of machine)

2. The needle is damaged

replace with new needle

3. The wrong size needle is being used

Choose a needle to suit the thread & fabric

4. The foot not attached correctly

Check & attach correctly

it's also possible that the machine could be slightly out of time

the best solution for the sewing machine is to take the machine
to a sewing machine shop & have it serviced, to find out why it's
stuck in position A. that way you will know wether it's needs cleaning
& new oil & grease or if some part is damaged or not.

what's the name & model of the machine?

it's very possible that the machine is slightly out of time & needs to be service at a sewing machine shop
is the fabric & thread & needle compatable with each other?
did you use every thread guide when threading the machine?
is the bobbin in correctly?
is the bobbin warped?

There are two tension adjustments, which should be done with a proper set of weight gauges - top and bottom thread tension should be carefully balanced to get the best stitch formation. It is best that you assume the top tension is correct and adjust the bobbin tension to match. Load the bobbin with thread of one colour and put a spool of the same thread but a different colour on the top. Thread-up the machine, load the bobbin and sew-off a satin-stitch on max width zig-zag. In this configuration, there should be a very small 'bead' of the top thread showing along each side of the satin-stitch on the underside of the material. If there's excessive top showing, the bobbin tension is too high and if none, the bobbin tension is too low. To adjust the tension, remove the bobbin case and you will see a spring around the edge with two screws through it. One of the screws holds the spring in place and the other adjusts the tension - this is furthest from the edge of the spring and is in a small 'cup' in the spring itself. To reduce tension, turn the screw VERY SLIGHTLY anticlockwise and to increase it turn it clockwise. Make very slight adjustments and re-check sewing-off the satin-stitch every time until you get the required thin line of top showing down each side of the stitch on the underside. Ideally this should be done with Mettler Metrosene thread, but as we're just balancing against the top tension, it shouldn't matter too much provided you use a good thread top and bottom.

You need a foot like this one so you can guide the folded edge of the fabric hem along against the white plastic foot. This is a generic style snap on blind hem foot, your machine should have one in the accessories that looks like this if your machine has a blind hem stitch included in its functions.

You fold the fabric into a upside down Z shape and run the top folded edge along the white guide with the fabric under the foot, hard to explain but once youve done it once, it makes sense.

You need to select the stitch on your machine that looks like 3 small zigzags, then one bigger one, or 3 straight stitches, then one zig zag to the side. This is the blind hemming stitch. You'll possibly also have a blind hemming foot to use, which helps with guiding the fabric fold into the machine and keeping it even. But if not, you should be able to buy one from your Huskqvarna dealer or a generic one from www.sewingpartsonline.com may well fit.

You'd be best served by visiting http://sewing.about.com/od/techniques/ss/machineblindsti.htm for photos and intructions if you've never done blind hem stitching before.

Blind hemming works best when hemming straight edges of fabric such as a ruffle on a full skirt - if there is any curve in the seam, it gets much harder and the result won't look so good. In essence, you press the fabric hem up, then fold the hem edge back under so you have a "S' shape, then sew along the single layer with the folded edge sitting against the foot guide. Then when the machine takes the 4th wide stitch, the needle swings to the left and catches a small stitch into the upper folded layer, then back onto the hem. The trick is adjusting the stitch so that the wide stitch doesn't show much on the right side of the garment

As to your question about leather, the 6460 has a special stitch for sewing leather. Select Colormatic cam C and install in the cam hole at the back of the machine. To remove/add a cam turn the upper left hand dial on the front of the machine to the small dot. This disengages the cam. Gently remove the cam by pulling straight out from the back of the machine. Install cam C straight in, ever so slightly twisting it back and forth into the hole to find the sweet spot. You'll hear a click when it's all the way in.

To use Viking's leather stitch, turn the upper left dial to the color yellow. (Note: The slash line on the upper left dial is a stop. You can't turn past that point. Go in the other direction to get to the icon or color you want.) Turn the upper right and bottom right dial to yellow also. The upper left dial is what selects the particular stitch on the cam, the leather stitch in this case. The upper right dial selects stitch length, and the lower right dial selects stitch width. You can move the right dials within the color range. Experiment on a scrap of cloth to get the stitch size the way you want it. The leather stitch looks like a straight stitch with a block style edging to the right of the straight stitch. This is supposed to give a stronger stitch to the leather rather than a straight stitch by itself.
If you don't have the manual for your machine: Select which of the eight cams you want to use. All the cams are removed/installed by turning the upper left dial on machine front to the small dot. At the rear of the machine, pull/insert cam straight in or out and twist slightly as you push in or remove to find the sweet spot. Move the dial away from the small dot to lock the cam in.
Turn upper left dial to stitch type you want and match the other dials to that same color. Upper right controls stitch length, lower right controls width. Bobbin tension is controlled by the dial at front left of the machine, above the needle.
Cams A-C are the workhorse cams and the rest are embroidery stitches.Straight stitch, button and stitched zig-zag will work on any cam. These stitches do not rely on matching a color code. To use those three: To select straight stitch, on the upper left dial, choose the icon that looks like a buttonhole with a zig that trails off to the right. Select stitch length on upper right dial and turn the lower right dial to zero, going by number rather than color.
To select stitched zig zag, turn upper left dial to the broken zig zag icon (to the right of the straight stitch icon). Select stitch length and width.
To move the needle to the side for buttonhole stitching or other times when you want the needle off center, turn the upper left dial to the button icon. If stitching a button hole, set stitch length to zero and lower right dial to desired stitch width. Push in the small white button that's beneath the lower right dial in order to prevent the feed dogs from moving the fabric forward. Pushing that button in is also handy for putting cloth under the foot before sewing as it prevents snagging and is used for tacking.