Drill Press Accuracy Questions
 

I have a 12" Delta drill press (11-990 C), approx 10 years old, used
lightly for wood working, now being used more and more for metal . I
have 2 questions about it.

1) The bit seems to deflect when drilling into anything other than a
perfectly flat wooden surface (hex, rounds, on an angle, etc).
Feeding slowly doesn't really seem to help. Using a centre drill
first helps, of course, but in my newbie opinion, it seems to flex
more than it should. I can't find anything to adjust or tighten or
????? Any suggestions?

2) The table height adjustment is a rack and pinion. The rack is not
rigidly attached to the column, so any height change causes the table
to rotate around the column, destroying any set up accuracy. The OE
retaining ring won't tighten enough to hold the rack (I've split 1
already!). Should I pop a screw through the rack into the column to
hold it in place? Or am I expecting my drill press to behave like a
milling machine?


Thanks,
Chris

Drill Press Accuracy Questions
 

Chris wrote:
I have a 12" Delta drill press..


1) The bit seems to deflect when drilling into anything other than a
perfectly flat wooden surface (hex, rounds, on an angle, etc).
Feeding slowly doesn't really seem to help. Using a centre drill
first helps, of course, but in my newbie opinion, it seems to flex
more than it should. I can't find anything to adjust or tighten or
????? Any suggestions?

um, "deflect". Do you mean it wanders and the hole doesn't start where
you think it should start? This is a function of the geometry of the
end of your drill bit and also how "whippy" the drill bit is. A really
rigid drill bit like a center drill shouldn't wander much if the surface
is flat. If the surface is curved, then you can get much better results
by cutting a small flat and starting the drill on the flat. For wood,
this flat can be done with a small chisel or something (I'm no wood
guy) and for metal, it can be filed.

2) The table height adjustment is a rack and pinion. The rack is not
rigidly attached to the column, so any height change causes the table
to rotate around the column, destroying any set up accuracy. The OE
retaining ring won't tighten enough to hold the rack (I've split 1
already!). Should I pop a screw through the rack into the column to
hold it in place? Or am I expecting my drill press to behave like a
milling machine?

You're correct, changing the table height loses your setup. This is a
small inexpensive drill press, not a mill. Even if your rack were welded
to the column you'd still lose some accuracy. Learn to locate your
workpieces under the spindle axis. For many parts this can be done just
by holding the workpiece on the table and letting it move a little as
the drill bit picks up the indent. For many other parts this is too
dangerous as the drill can catch at breakthrough and spin the workpiece,
perhaps tearing a hole in your stomach. One approach I used to use is
to use an X-Y drill vise mounted instead of the table. I got a whole lot
of use out of that one. Beware that the quality varies hugely on those.
I hand-picked mine from a bunch up at the Grizzly showroom 10-12 years
ago, and it's real nice. I got a slightly bigger one from J&L a few
years later and it was awful. None of them work perfectly. They all
work better than a hand drill.

Really, my current best advice is to find a motivated seller of a
mill-drill and get one of those. Those are lousy mills but real good
drill presses.

Grant Erwin
erstwhile author of http://www.tinyisland.com/htbdrillp.txt

Drill Press Accuracy Questions
 

I have seen people use a hose clamp to firm up the rack. That age Delta is
more than likely an import.

Drill Press Accuracy Questions
 

"Grant Erwin" wrote in message
...
snip-------

Really, my current best advice is to find a motivated seller of a
mill-drill and get one of those. Those are lousy mills but real good
drill presses.

Grant Erwin


Well said, Grant.

Harold

Drill Press Accuracy Questions
 

Grant wrote:
um, "deflect". Do you mean it wanders and the hole doesn't start where
you think it should start? ...

English really is my first language, even if it doesn't show
sometimes.

The point of the bit makes 1 move, in one direction - it doesn't move
in a circle or make random motions. I could be convinced that it is
the chuck that is moving, rather than the bit flexing, too. I don't
see any sort of nut or screw or drawbar or ??? holding the chuck to
the machine, so I'm not sure how I would tighten it if this is indeed
the case.

I think your suggestion about the mill-drill is probably the right
solution.

Chris

Drill Press Accuracy Questions
 

OK. Don't be so disparaging, not everyone is a skilled technical writer.
Do you mean that if you chuck up a drill bit, power off, grab the outside
of the chuck and wiggle that there is tangible side play in one or more
directions? That would be terrible if so. Or do you mean that if you put
a workpiece on the table, chuck up a drill bit, start the motor, and as
you lower the drill bit into the workpiece as it touches it "skitters"
around a little? These are two very different issues and I'm still not
clear on which you've got going on.

Grant

Chris wrote:
Grant wrote:

um, "deflect". Do you mean it wanders and the hole doesn't start where
you think it should start? ...


English really is my first language, even if it doesn't show
sometimes.

The point of the bit makes 1 move, in one direction - it doesn't move
in a circle or make random motions. I could be convinced that it is
the chuck that is moving, rather than the bit flexing, too. I don't
see any sort of nut or screw or drawbar or ??? holding the chuck to
the machine, so I'm not sure how I would tighten it if this is indeed
the case.

I think your suggestion about the mill-drill is probably the right
solution.

Chris

Drill Press Accuracy Questions
 

In article ,
Chris wrote:
Grant wrote:
um, "deflect". Do you mean it wanders and the hole doesn't start where
you think it should start? ...

English really is my first language, even if it doesn't show
sometimes.

The point of the bit makes 1 move, in one direction - it doesn't move
in a circle or make random motions. I could be convinced that it is
the chuck that is moving, rather than the bit flexing, too. I don't
see any sort of nut or screw or drawbar or ??? holding the chuck to
the machine, so I'm not sure how I would tighten it if this is indeed
the case.

I think your suggestion about the mill-drill is probably the right
solution.

It will help -- but what may help more is to get split point
drill bits. Normal drill bits have what is known as a "chisel point" --
a bar across the center which really does not cut, and which on any
irregular surface (or even on a smooth surface if you are coming in at
an angle) will sort of "walk" on the ends of the chisel point until the
bit deflects enough so the added force needed is sufficient to allow it
to start to bite in.

A split-point has a more complex tip geometry, which terminates
in a relatively sharp point which will not walk. That would help you
get these bits started where you want them.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Drill Press Accuracy Questions
 

Grant wrote:
Do you mean that if you chuck up a drill bit, power off, grab the
outside
of the chuck and wiggle that there is tangible side play in one or
more
directions? That would be terrible if so. Or do you mean that if you
put
a workpiece on the table, chuck up a drill bit, start the motor, and
as
you lower the drill bit into the workpiece as it touches it "skitters"
around a little? These are two very different issues and I'm still not
clear on which you've got going on.

Once more into the breach...

1) power off, bit in, quill retracted: no noticeable side to side
play. a very little bit of rotational play (as described in your
article on spline wear).
2) power on, bit in, quill extended until bit contacts work: bit moves
off target (centre punch or mark)slightly, then digs in and starts
cutting.

Thanks for your patience.

Chris

Drill Press Accuracy Questions
 

2) power on, bit in, quill extended until bit contacts work: bit moves
off target (centre punch or mark)slightly, then digs in and starts
cutting.

For this to mean anything you have to define "slightly". Does it move 1/2
the drill bit diameter, 1/4, 1/8 ?? Does it skitter around a little as
Grant asked and then drill to center? Does it skitter around and then drill
to a circumference of the skitter pattern ?

Bob Swinney

"Chris" wrote in message
om...
Grant wrote:
Do you mean that if you chuck up a drill bit, power off, grab the
outside
of the chuck and wiggle that there is tangible side play in one or
more
directions? That would be terrible if so. Or do you mean that if you
put
a workpiece on the table, chuck up a drill bit, start the motor, and
as
you lower the drill bit into the workpiece as it touches it "skitters"
around a little? These are two very different issues and I'm still not
clear on which you've got going on.

Once more into the breach...

1) power off, bit in, quill retracted: no noticeable side to side
play. a very little bit of rotational play (as described in your
article on spline wear).

Thanks for your patience.

Chris

Drill Press Accuracy Questions
 

OK, now I've got it. This can happen on any drilling or milling machine.
You simply need a more rigid setup. Use a shorter drill bit, or a center
drill, just to get things going. I once bought about 5 6" long center
drills. I use those when I'm going to drill with a bigger drill, like
a 1/2" drill bit. Those are longer, and so I need more headroom above
the table. I can still get down to the workpiece if I use a long center
drill. Once you have the hole started, then use a skinny drill bit to
go through. If the material is at all tough then pay strict attention
to your speeds. 75 surface feet per minute is pretty good for HSS drills
cutting steel. Take 300 and divide it by the diameter in inches to get
a rough RPM. For instance, a 1" drill you'd run at 300 rpm. Or a 1/8"
drill you'd run at 2400 rpm. Point is, don't run a small drill bit
slowly. Bad things happen. I bought a whole box of 1/8" drills, top quality,
best I could buy, because I so often drill my first hole with that size.
Once you've got a through hole, on your little drill press I would step
up slowly to your desired size, because that will minimize the forces
deflecting your table.

A long skinny bit will almost always skitter on a new surface. You can
sometimes get away with a short skinny bit i.e. a screw machine drill.
Or you can center punch your holes and follow up your accurate centerpunch
with a big whopping centerpunch you drive in with a 2 pound hammer. I know
a good machinist who does that and his drills don't wander because his
centerpunches catch the bit.

Grant

Chris wrote:

Grant wrote:

Do you mean that if you chuck up a drill bit, power off, grab the

outside
of the chuck and wiggle that there is tangible side play in one or
more
directions? That would be terrible if so. Or do you mean that if you
put
a workpiece on the table, chuck up a drill bit, start the motor, and
as
you lower the drill bit into the workpiece as it touches it "skitters"
around a little? These are two very different issues and I'm still not
clear on which you've got going on.

Once more into the breach...

1) power off, bit in, quill retracted: no noticeable side to side
play. a very little bit of rotational play (as described in your
article on spline wear).
2) power on, bit in, quill extended until bit contacts work: bit moves
off target (centre punch or mark)slightly, then digs in and starts
cutting.

Thanks for your patience.

Chris

Drill Press Accuracy Questions
 

Somehow I often do things almost exactly the opposite of Grant. I
usually use a slender drill that is long and has a lot of flex. I do
centerpunch with a automatic center punch so that with a small drill
the center punch dent holds the drill from slipping. With the part is
a vise, but the table able to be moved, I move the part so the drill
is no longer flexed to one side. That is the drill is exactly over
where I want to drill. Then clamp the table from moving. Then I
apply some pressure and after the drill has the drilled the hole out
to the drill diameter I apply more pressure and drill through the part
with the slender drill. Then I go to the full size drill for the hole
that I want.

I am sure the way Grant said will work well, it just is not what I do.

Dan



Grant Erwin wrote in message

Drill Press Accuracy Questions
 

Dan sez:
" I am sure the way Grant said will work well, it just is not what I do."

Your choice, of course. But with your "system" you would do nearly as well
with a hand held drill. Grant's advice was for machinists.

Bob Swinney


"Dan Caster" wrote in message
...
Somehow I often do things almost exactly the opposite of Grant. I
usually use a slender drill that is long and has a lot of flex. I do
centerpunch with a automatic center punch so that with a small drill
the center punch dent holds the drill from slipping. With the part is
a vise, but the table able to be moved, I move the part so the drill
is no longer flexed to one side. That is the drill is exactly over
where I want to drill. Then clamp the table from moving. Then I
apply some pressure and after the drill has the drilled the hole out
to the drill diameter I apply more pressure and drill through the part
with the slender drill. Then I go to the full size drill for the hole
that I want.


Dan



Grant Erwin wrote in message

Drill Press Accuracy Questions
 

Straight holes with the chuck aligned with the hole so it can be used
to guide a tap. What more would a machinist want? I could do it with
a wiggler instead of a flexible drill, but it would take longer. Try
it when drilling a hole in a piece of round stock before deciding that
it won't work well.

Dan


"Robert Swinney" wrote in message ...
Dan sez:
" I am sure the way Grant said will work well, it just is not what I do."

Your choice, of course. But with your "system" you would do nearly as well
with a hand held drill. Grant's advice was for machinists.

Bob Swinney