Originally Posted by Tombstone0
All that will do is make your hydrometer tube shorter. It won't mean you'll need any less beer to take a reading.
Most likely this will make the tube shorter than the hydrometer and you won't be able to use it at all, at least not for any readings above the top of the tube.
I think the OP is talking about this type of test tube :
it's 14.5 inches long, unfortunately hydrometers are much shorter, meaning you have to fill the tube with more wort just so the hydrometer sticks out for spinning, retrieval and such.
Chopping it shorter means you can use less wort and still access your hydrometer.
I have no idea why they make them so tall, the extra width is nice, but the height is a waste.