Texatdurango
Member
It is widely accepted that using a center drill is the most accurate way of drilling a starter hole in a blank to be followed by a larger drill. The reason the center drill is so accurate is that it is short and rigid with no flutes so it doesn't wander around when drilling end grain.
I was browsing through a tooling catalog recently and a set of drills caught my eye, they are called "Screw Machine" drills and they differ from the traditional "Jobber" drills in that they are about half as long!
Since I do all my drilling on the lathe and with some bits protruding almost 5" beyond the drill chuck, I was intrigued with the idea of having a shorter, more rigid drill to not only drill my starter holes but the final holes as well.
I ordered a set of the machine drills, tried several sizes out drilling wood, acrylic and truestone blanks and immediately noticed a big difference, the occasional "chatter" or "drift" was gone. Nothing but nice quiet drilling!
I don't own stock in any tool company, am not selling bits, and am not advocating anyone running out and buying a set of these bits but if you are experiencing the occasional "bit wobble" where you have to hold onto the drill chuck for dear life, then perhaps you might consider trying one of these shorter bits.
Most of the blank drilling I do is on blanks around 2" give or take a few tenths and all of the drill bits I bought are capable of drilling holes that deep. Google "machine drills" and you'll see lots of suppliers who carry the drills.
Just something to think about!
They say a picture is worth a thousand words so to keep from typing all night, here are a few shots I took:
Here is a typical center drill, note the short length.
Here are the same size drills in "screw machine" and "jobber" lengths
Here is a handful of screw machine drills and jobber drills they replaced
Here is what I see when drilling with a jobber drill, note the total length! That's almost 5" of bit sticking out to drill a 2" hole.
Here is what I see when when using a screw machine drill, almost as short as a center drill... and just as rigid!
I was browsing through a tooling catalog recently and a set of drills caught my eye, they are called "Screw Machine" drills and they differ from the traditional "Jobber" drills in that they are about half as long!
Since I do all my drilling on the lathe and with some bits protruding almost 5" beyond the drill chuck, I was intrigued with the idea of having a shorter, more rigid drill to not only drill my starter holes but the final holes as well.
I ordered a set of the machine drills, tried several sizes out drilling wood, acrylic and truestone blanks and immediately noticed a big difference, the occasional "chatter" or "drift" was gone. Nothing but nice quiet drilling!
I don't own stock in any tool company, am not selling bits, and am not advocating anyone running out and buying a set of these bits but if you are experiencing the occasional "bit wobble" where you have to hold onto the drill chuck for dear life, then perhaps you might consider trying one of these shorter bits.
Most of the blank drilling I do is on blanks around 2" give or take a few tenths and all of the drill bits I bought are capable of drilling holes that deep. Google "machine drills" and you'll see lots of suppliers who carry the drills.
Just something to think about!
They say a picture is worth a thousand words so to keep from typing all night, here are a few shots I took:
Here is a typical center drill, note the short length.
Here are the same size drills in "screw machine" and "jobber" lengths
Here is a handful of screw machine drills and jobber drills they replaced
Here is what I see when drilling with a jobber drill, note the total length! That's almost 5" of bit sticking out to drill a 2" hole.
Here is what I see when when using a screw machine drill, almost as short as a center drill... and just as rigid!
Last edited:
