And by "good" I guess I mean "extensive".
I took home a project the other night. Some Noro Silk Garden and the Jane Ellison Designer Mini Knits pattern book. I am making Design #26, which is a cute short sleeved raglan top, with a button closure at the neck. The gauge is 18 sts to 4" on a size 8 US needle, or 4.5 sts/inch. I typically go down one size for needles, so I pulled out my 7 US Addi Turbos and started swatching. After a nice 4 inch swatch my gauge measured 4.25 sts/inch. Only .25 stitches off, so no biggie, right? WRONG!
Had I gone ahead with that needle size, the back of the sweater would have been an inch too large. and the front would have been too large as well. See 82 stitches divided by 4.5 sts (the correct gauge) = 18.25 inches. But 82 stitches divided by 4.25 = 19.3 inches.
So I pulled out my size 6 Addi Turbo needles. And swatched. Typically (and this is not ALWAYS the case) your gauge should change 1/2 stitch for every needle size you go up or down. INCREASE your needle size, your number of stitches per inch should GO DOWN 1/2 st. And DECREASE your needle size, your number of stitches per inch should GO UP 1/2 st. And in this case, this happened to me. My gauge on size 6 Addis was 4.75. But do the math... 82 stitches divided by 4.75 sts (the correct gauge) = 17.3 inches, this time an inch too small.
Luckily, I own a Denise Interchangeable Knitting Needle Kit. I normally use it for emergencies - when I can't find my Addis, or when I am travelling and want all of my needles in one handy case. But yarn slides very differently over Addis than it does over the plastic Denise needles. So it stands to reason that my gauge should be different. I pulled out the Denise 7s and BINGO! 4.5 stitches to the inch.
But beware, the danger of the Denises...
I cruised throught the back of the sweater, and then finished one front. As I was getting ready to bind off the front, I happened to look at the needle in my right hand. It had a "5" stamped in it. Egads! After I had finished my ribbing on size 5 needle tips, I had only switched ONE needle tip to the size 7. So I just had knit the whole front with one 5 and one 7. Gauge? Yes, it was off. So frog, frog, frog.
It's a good thing I really like knitting with this yarn. :)