Looking for any tips/tricks for drilling a hole w/a drill press that's as
close to dead-center to a specified point as possible.
Here's what I've been doing - I have the position marked with graph paper
that's taped to the workpiece. With the help of a magnifying glass, I
painstakingly move the piece until the tip of the bit is aligned with the
conjoining lines. By aligning with the tip I mean I view the tip both from
the narrow or "pointy" persepective within the channel of the bit and then
turn it 90 deg and look at the the wider perspective, and view it from the
side and front to make sure I have it aligned with both the X and Y axis.
When I finally get it so the tip is as centered as I can make it whichever
way the bit is turned and in relation to both axis, I clamp the piece to the
plate of the drill press and drill the hole. However, on examination, the
hole comes out obviously not dead center in relation to the graph paper
I've also tried aliging it with the drill running, going visually by where
the "point" appears to be when the bit is spinning. I get somewhat better
results this way but wonder if there's a more precise and dependable way of
achieving a centered hole.
Thanks for any input.
I second the recommendation of a centering bit to align
If drilling with thin bits, using something like a Starrett center
punch to pre-position the starting location would also help prevent
the bit from "walking" away from the point you want it to drill at
Without a spotting pip, you'll never, never get your hole dead center
that way. A drill press will be too loose for it and the drill will
always skate. Some of the guys will recommend using a spotting drill
to start with. You can get within a couple of thousandths using one of
the optical center punches where you line up the mark in the crosshairs
and then substitute the marking punch. That would probably be the best
method for what you've described, if it's a one-off. Using stub drills
will help, too. Get name brands, cheapy chink ones will do you
absolutely no good at all.
There's other methods, but if all you've got on hand is a drill press,
suggesting use of a vertical mill is kind of useless. Guy Lautard
details a poor-man's jig borer for drill press use in one of his later
Bedside Reader series but you aren't going to make that up with just a
drill press on hand, either.
Get a center finder- used to use them in machining all the time--
simply a 1/4" rod with a 30 degree cone machined on one end. Helps to
center punch the center of the hole on the workpiece first, as the
indentation will provide an easy physical reference for the end of the
Chuck it in the drill press
Find the center of your drill hole- you may want to lock the quill at
Clamp the work to the table-- unlock the quill
Change out the center finder with the bit you will use
The usual way is to use a centerpunch.
Most of the time I use an automatic centerpunch to start, then deepen it
with a "manual" centerpunch and hammer.
Auto-centerpunches are available at most any hardware outlet, less than
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First tip: use an awl or center punch (depending on whether it's wood or
metal you're drilling) to mark the precise location of the hole first.
Even with a brad point bit, it's difficult to prevent drills from wandering
off the target when they enter the material. The smaller the gauge of the
bit, the worse the problem is.
Second tip: depending on the nature of the work involved, you may be able
to use a cross-slide vise for fine positioning of the work relative to the
bit. They only work on stock that can fit inside the jaws, but they are
quite useful to have when precision matters.
Something like this:
Now, whether you have one of those handy gizmos or not, position the work
(with the hole locations pre-punched), then pull down the quill with the
motor off. Listen for a plinking sound, and watch with hawk eyes for the
slightest bit deflection. If the bit is deflecting to enter the dimple,
your hole won't come out right.
I find it helpful to rotate the chuck by hand to position the flutes or
other cutting edges in a way that allows a clear view of the very tip of
the point in relation to the dimple. Repeat the process of making fine
adjustments to the X and Y axes and then checking with the quill until the
bit enters straight and true, then drill the hole.
This process is tedious and time consuming, but if there's a better way to
ensure a hole as close to perfectly placed as possible with a drill press,
I haven't discovered it.
Michael McIntyre ---- Silvan < firstname.lastname@example.org>
Linux fanatic, and certified Geek; registered Linux user #243621
if you have a 2 inch diameter piece for instance, set a pair of dial
calipers[preferably the 15 dollar chineses ones] a tad over half, say
1.015. scribe a number of lines near the center of the shaft from
different points on the circumference. Of course layout die[read
sharpie] makes it easier to see. You will end up with a pattern grouped
around the center, making it much easier to see if you are in error when
you center punch it. I prefer solid punches to the automatic ones,
sharpened to a nice sharp point.
Tap very lightly the first time, so if it is visibly out of center, you
can fix it.
drill with a small center drill or a 1/8 inch drill. drill progressively
Much of this relates to your eye; if you can see[and care about] the
error or not. If your scribe marks are ~.03 apart, the average person
can 'see' ~.005 error, if they want to.
Your answer below is right on, however, please tell me what is wrong with
this amateur approach.
Center punch the material, rather deep. Enlarge by using a centering drill
in the drill press, BUT, assuming the project is quite small (one or two
pounds) let it float on the table and have it center itself as you start
drilling. You seemingly end up with no drill bit deflection and, I assume,
a hole that is quite close in location to your initial center punch.
I know that I am a mere amateur, but it seems like every time I fasten a
product to the table, I end up with drill bit deflection. When it is light
enough to float and self center, I get better hole location.
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
Turn a sharp point on a bit of thin bar in the lathe and use that in your
drill chuck to centre on your graph paper. Ideally make it with a collet
chuck or 4 jaw chuck to get it dead concentric. Then use a centre drill to
start the hole before drilling right through.
Your pointy bar will also come in handy for setting tool heights exactly on
centre on the lathe. I have a couple of them in various sizes made out of
old engine valve stems and bits of ground silver steel.
Easy to make these. Next time you are in a machine shop supply get some
metal dowel pins. (They are cheap, a good hardware store might have them
also.) Chuck them up in your hand drill and spin them when you grind the
point, being sure to have a little cup of water to cool the point as you are
The op didn't say what material he was trying to drill but in some instances
you can get close to the center punched point and let the work float into
position under the spinning drill bit. If he is drilling wood, a brad point
is in order.
Another way would be to position a piece of Plexiglas that has a guide
bushing centered on a set of cross hairs. Then you can extend the reference
lines on the graph paper and the center will then be right over the target.
About the time I had mastered getting the toothpaste back in the tube, then
First of all, forget "absolutely dead center" -- that term is incompatible
with a drill press. A drill press is a tool for rapidly putting holes within
a reasonable tolerance of where you want them. That being said, this problem
breaks down as:
1) making the hole start directly under the spindle axis (i.e. preventing drill
bit wander) which is done by centerpunching and also by using very rigid drill
bits known as "center drills" which you can get at http://www.mscindustrial.com
2) putting your centerpunch mark exactly where you want it which is easy to
do within ten thousandths but very hard to do closer than two thousandths. This
is done for high precision by the use of an optical center punch.
Holes that have to be very precisely located aren't drilled, they are bored.
The machine that does this is a jig borer.
Most woodworking tolerances are on the order of .010" so you can probably
get away with learning to do layout and centerpunching. Once you have a
centerpunched mark, then it's also tricky to get it lined up exactly under
the machine's axis.
All of this supposes that your drill press table is at precisely right angle
to the spindle axis, and that your drill chuck has zero runout, neither of
which is likely true, especially if you're using something you bought at
You got to drill a center punched mark with a very small drill. Then
drill the hole larger with the next size or two up. Recheck the
locantion and if it is off, hit the top edge of the hole with a punch on
the side of the hole you want the hole to move to.
You could also drill the hole a 32th under size and then go through it
with the proper size end mill if your drillpress quill is stiff enough,
or drill another block with the finishe size and clamp that block in
place and use that to hold the endmill on center useing it as a guide
The problem is not so much your alignment, as the fact that unless the
end of the drill is perfectly symetrical and equally sharp on both
cutting edges, it has a tendency to wander off.
You don't say how big the hole is. If it's small, a full length drill
is very hard to control because there's so much flex in the shaft.
Instead use a center drill like these to start the hole:
If the hole is larger than 1/4 inch, use a spotting drill like one of
Short, stocky drills like that don't wander around when their cutting
tips meet the work.
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