I need to drill a hole in a shelf that's half an inch deep but I don't want to drill a hole through the shelf. What's the best way of doing that? I have a drill and i was thinking of showing just a half an inch of the drip bit. This way, I can force the drill to drill all the way to the end of the drill bit and not go through the shelf. However, a part of the drill bit's thread is being held by the drill for grip. Would using the drill and the drill bit in this way cause damage?
Yes, the drill chuck will mar the finish of the shelf. There is a slight chance of damage to the chuck. Plus, choking down on the bit, like that, obscures your view of the hole (the drill and chuck block it) -- making precision harder to accomplish.
The correct way to do this is to use a drill stop.
Drill stops are less likely to slip than tape or zip-ties, and are much better for precise and/or repeated drilling.
If marring the finish is an issue, clamp a piece of 1/8th plywood over the site and adjust the drill stop accordingly.
PS: A piece of wood over the hole is usually a good idea anyway, when drilling finished surfaces. It helps reduce both splintering and the scratching that occurs when flakes of drilled wood or metal whip around the bore site.
I usually just wrap a piece of masking tape around the drill bit leaving the correct length exposed. You can either wrap enough layers of tape around so that it is fairly thick, or leave a "flag" of tape sticking out. Either way will let you drill to the proper depth without the risk of marking the surface. The metal jaws of a drill can easily damage the surface if you allow them to come in contact.
you can use a bit of scrap wood that is the length of the expose drill bit minus the depth you want to drill so that when fully drilled through with the chuck touching the scrap it will only leave the desired drill depth exposed
this way you can use the scrap as a guide as you drill and also ensure the hole is square
that or use a drill press if you have one.
There is also that stuff that you always leave in the box when you get a new drill... (if your drill is equipped with a drill stop) then this is when you would use it.
The easiest and cheapest way that I have found is to use a drill stop on your drill. One that works well, and costs very little, is the Century Drill and Tool 73512 Adjustable Drill Stop". The two pieces are both plastic, but extremely strong plastic, that will last years, and because it is plastic, it hardly ever leaves any marks on the wood. It works with 1/4" to 1/2".