Why Hand Slides Require Careful Handling
The hand slides of the slide trombone are delicate and require careful handling. The brass outside slides have a wall thickness of from .011" (11 thousandths of an inch) to as little as .006" (6 thousandths of an inch), on the lightweight models.
Since an ordinary human hair is about .003" (3 thousandths of an inch) in diameter, the thickness of the outside slide's wall is equivalent to the combined diameters of about three fine human hairs. Consider a tube which is over four feet long made of brass which is only three hairs in thickness and sometimes is only two hairs in thickness. Further consider that this tube must fit over another tube so that the outside diameter of the inside slide is only .006" less than the inside diameter of the outside slide; that makes the clearance on each side between the stocking of the inside slide and the inside of the outside slide only .003" (three thousandths of an inch) or about the diameter of a human hair!
Using other comparisons, an ordinary sheet of bond writing paper is about .003" thick, a cigarette paper is about .001" thick. Consider an outside slide made of brass whose wall thickness is equivalent to three thicknesses of bond paper; some slides arc the thickness of only two such sheets of bond paper. Consider also that the clearance on a side between the stocking and the outside slide is equivalent to the combined thickness of three cigarette papers tightly compressed together.
These thicknesses and clearances are emphasized because too few trombone players realize how delicately their hand slides arc made. When you think of your hand slides in these terms you'll give more respect and consideration to them.