Inconsistency

I go through periods with my 3 iron where i will either hit it really well or i wont, does anyone know how to stop the inconsistency

OK, if you read the thread I started earler,
(http://www.golf-tuition-online.com/g...aws-swing.html (What Really Matters? – Immutable Laws of the Swing))

..... you'll know what I'm going to say.

If you start with a decent swing but are inconsistent, the cause is likely to be a changing spine angle through the swing. Of course, this is likely to show up on most of the longer clubs to the greatest extent. So, check this aspect of your swing, along with the possibility of excessive swaying. I find, though, that if you maintain the spine angle throughout, a lot of other things, such as take away, plane and rotation, take care of themselves.

Long irons are one of the most notorious clubs in the bag to suffer this from - Padraig Harrington maintains that unless you're a low handicap golfer, you shouldn't carry anything lower than a 3I, replacing them with hybrids instead...