Steady rests are handy tools, they make several fairly common wood turning problems much easier. The two most common issues people have are turning long spindles and hollowing deep jars.
Turning long spindles
By spindle, I write of anything long and relatively thin. A walking stick would be in this category, or even a candlestick. As a spindle is turned thinner, it becomes more flexible so as your chisel applies pressure, the piece will bend. Chatter and general difficulty ensue. The piece is well supported close to the chuck, and at the other end of your lathe next to the tail-stock. Between the two, in the centre of the lathe, it is least supported. A steady rest placed next to where you are applying pressure will solve this problem. It will fix your piece firmly in place whilst allowing it to rotate.
However it is possible to brace your piece with your free hand – it’ll help a bit, not as much as a steady rest, but a lot of people get by well with this technique providing the spindle isn’t especially too long or too thin. Hollowing projects however, are not so easily hand braced.
Hollowing deep jars/pots/goblets
When hollowing a deep jar, it can feel as if you are placing a risky and time consuming bet. You’ve spent hours making the piece, you’ve got the outside perfect, you’ve turned a nice spindle, so now its time for the hollowing. A catch or a wobble can destroy your piece or even pop it off the lathe – and it’ll happen quicker than you can react. You’ll survive but the piece will be in…. pieces. Its a frustrating moment when making any craft: Do I risk it and continue? or do I quit while I am ahead? A steady rest can greatly reduce the risk of destroying your piece, and add a great deal of stability for chatter free turning. Without a steady rest, the benefits of a heavy and rigid lathe are lost as you move further from your chuck or tail-stock. Cantilevered pieces (held only at one end) are especially vulnerable to wobble. All things being equal, length, cross section, material etc, a piece held at one end only will be deflected many times further than one held at both ends – or one held with a steady rest.