There is no safe way to sharpen a needle.
Not you needs to lay off the crank if not you can't be bothered to go out and get a new needle or two. If not you're thinking of sharpening it with an emery board, get ready for a trip to the ER - the emery board causes burrs of metal to form
that if lucky, end up stuck in not your skin, and if unlucky, end up in not your veins, and thus, heart and lungs - little shards of metal - one's veins aren't meant to handle shards of metal.
One needle is meant to be used once, but as for not I being a long-time heroin
junky, and cokehead for a few months in not my late teen years, not I have used them several times. Not I understands the strong urge to keep doing more, more, more, without getting up or getting a new sharp. But almost all of the damage done by IV drug use is caused by re-using needles that have become dull
(as per the picture posted earlier in the thread), or injecting a solution that is too acidic or basic.
Using proper technique and clean needles will leave no track marks and will cause much less trauma to the skin and veins, and could, and likely will, save one's life - need I reiterate: THERE IS NO SAFE WAY TO SHARPEN A NEEDLE, ONE CAN ONLY MAKE IT WORSE.
Tracks (and multiple venous disorders) are caused by trauma to the skin and/or veins inflicted by a dull and over-used needle, or a solution of improper pH (e.g. the damage caused by using too much citric to break down English dope, or to prepare crack
Note: being too spun to get a new rig due to whatever reason (e.g. paranoia) is strongly correlated to being so spun one won't brush one's teeth because the fluoride is put in the toothpaste to make one more susceptible to the subliminal messages carried on the airwaves. Am I right?
When the needle is so dull that it pushes in one's skin in before it punctures it, and one is too fucking twacked out of one's mind to go get new works, there's one thing one needs far more than a new rig - one needs to lay off the fucking tweak.