Why do drill bits get longer as they get bigger???

[whoaru99]

Well, I'm sure I can, but I'm just wondering why 90% of the drill bit sets sold have bits that keep getting longer and longer, especially since most of them wind up in homeowner's and handyman's shops and never drill a hole more than 2" deep.
It just seems like a colossal waste, especially on bit's over 3 1/2 -4" in length.

I think the best reason so far is one that was given a post or two back. If I read it right, it seems to say the length of the bit is proportional to the diameter to give the proper flute length for chip clearing.

 

[Cogito]

Standard bolts have a thread length of twice the diameter plus 1/4 inch. As the diameter increases, so does the thread length. Since drill bits are frequently used to drill for tapping, they need extra length as the diameter increases. Add to that the point, a shank for the chuck, and exposed flutes to clean out, you pretty much have it.

They make shorter bits that are "jobber" length, but they are also graduated.

FYI

Thread length on bolts of 6" or more are (2 X Diameter + 1/2"). This does not apply to structural bolts such as ASTM A307B, A325 or A490, which typically have a fixed thread length regardless of length.

There are many different lengths of drill bits such as "stubby" (Machine bits), "jobber", "aircraft extension" (6"), "Long Boy" (12"), etc...