Drill bits

Is there a logical reason for drill bits all being different lengths? When I
want to drill different sized holes on the same piece of material, it is a
pain in the neck because sometimes it changes the setup on my drill press.
Are there sets of same-length drill bits? Thanks -- Daven
Reply to
Daven Thrice
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I think the logical reason is that smaller holes are drilled shallower than large holes and that large-diameter drills are stronger and can be made longer than small-diameter drills.
I use a set of screw machine-length drills for all work that requires accuracy. They are quite a bit shorter than the normal jobber-length drills.
Reply to
Jim Stewart
A small diameter bit has to be short to prevent it from whipping, buckling, and breaking when used. Larger diameter bits can be longer while retaining a satisfactory diameter/length ratio. Now large diameter bits *could* be made shorter. That would lessen the difference in lengths between small and large bits. But as far as I know, no one makes a set like that.
Gary
Reply to
Gary Coffman
Now large diameter bits *could* be
Check out "stub" or "screw machine" drills
Reply to
randy replogle
Yes. Bigger holes also tend to be longer holes. Also the rigidity of a drill bit is a function of its length/diameter ratio. The smaller the drill the shorter it needs to be to work without deflection. You can buy "stub" drill bits which are shorter and more rigid and designed for more accurate on centre work but the length will still vary with diameter.
Anyway, ain't no thang to work out in advance which is the longest drill bit you'll need for a job and make sure the machine has clearance for that length before you start.
Reply to
Dave Baker
Even screw machine drills aren't all the same length. The smaller diameter ones are still shorter than the larger diameter ones.
Gary
Reply to
Gary Coffman
"Dave Baker" wrote
And, if accuracy isn't a problem, you can get those three footers that are made to drill in special circumstances.
Steve
Reply to
SteveB
Jim Stewart sez: "> I use a set of screw machine-length drills for
Good on you, Jim! Screw machine-length drills are stiffer, all things considered. If possible, I always follow the center drill with a screw machine length pilot drill.
Bob Swinney
Reply to
Robert Swinney
Dave sez: "> Anyway, ain't no thang to work out in advance which is the longest drill bit
Good advice- particularly for mill-drill owners.
Bob Swinney
Reply to
Robert Swinney
You've already gotten quite a few good replies. But there is one thing which I don't see mentioned, so I'll plunge into that.
First off -- what is the maximum diameter which you actually *need*?
In the range up to 1/8", there are a series of drill bits made with 1/8" shanks, so the small diameter part can be appropriate to the diameter of the drill.
These also tend to have split points (so they are less likely to "walk" when starting a hole on a level surface, and are available to amazingly small diameters.
These are typically solid carbide bits (though the shank may be steel). They are made and sold for automated machines drilling holes in printed circuit boards. Since no printed circut board is very thick (I would be amazed to see one as thick as 1/4", even with multi-layer), the flutes do not need to be very long, and these can be made a constant length.
They show up from time to time at flea markets, and usually have colored collars around the shank, to help pick the right size (with the right chart to look them up. :-)
But in all likelyhood, since you don't mention your needed hole diameters, at least some of them are quite a bit bigger than 1/8".
Another point which I did not see mentioned is that each resharpening removes a length of drill flute proportional to the diameter, so with the varying lengths, each will usually accept about the same number of resharpenings before becoming too short (and too thick in the web) to work well.
I guess that you could make a series of drill bit holders for the common sizes which would put the tip of each at about the same distance from the chuck, to get an approximation of what you want.
Good Luck, DoN.
Reply to
DoN. Nichols
Three foot? I have a five foot 5/16th drill I use for special occasions.
Reply to
Nick Hull
And I have a 10 footer with an auger bit at the end so I can drill from the basement to the ceiling in a wall cavity. Could go another 8 feet if I was feeling lucky!
Reply to
Rick
Hey, why *buy* stub drills? I have a pretty good set in the 1/8 to 1/2 range. Usually from resharpening full length ones I've broken :-)
Also for holes in the 1/2" to 1" range, the OP could consider 1/2" shank drill sets. These in my experience vary much less in length than the big taper shank drills. Before I got my radial arm drill I used to use these to step-drill holes because it was faster to swap them over than it was to drive out a TS drill and seat the next one. Now of course I just drill a pilot hole the correct size, then the full size hole. Slow speed & power feed make life simple.
PDW
Reply to
Peter Wiley
"Peter Wiley" wrote
Other than the lenght of the arm that comes out, is there any advantage to a radial arm drill? Why does the arm need to be adjusted? Are there dials on it that let you repeatidly reposition the arm?
I don't understand. Are you saying that, with a more powerful drill, you don't need to drill intermediate sized holes because this drill has the power to drill big holes?
dt
Reply to
Daven Thrice
"Daven Thrice" wrote
(I meant, "repeatably")
Reply to
Daven Thrice

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