I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

"woodworker88" wrote in message
...
snip--


My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

Grinding a chip breaker in a twist drill may not be in your best interest.
Here's a couple things to consider.

Drills are circular ground, so it's the margin that establishes the diameter
of the hole you drill. If, in the process of grinding the chip breaker, you
grind past the margin, the drill will cut undersized until it reaches the
full diameter margin, and likely bind, although it's also possible it will
simply open the hole to full diameter. All depends on how you grind the
chip breaker, and if you end up with relief in the proper areas.

The second consideration is, depending on how you grind the breaker, you may
actually be encouraging the hogging by increasing the rake angle. Rake
angle on twist drills is created by the helix, and is already rather
generous.

Are you familiar with the procedure used to blunt drills for drilling in
brass, and even cast iron? If so, what would serve you well is to grind
the drill in a similar fashion, decreasing the rake angle. Don't grind it
until it's zero rake, just reduce the angle. That will discourage the
drill from hogging and likely perform without the problem you spoke of.

Be mindful that when you grind your drill, you face the same problem as when
grinding a chip breaker. You must not grind past the margin. It does no
harm to grind more towards the web, removing only a bare minimum at the
margin.

Harold

If I understand correctly, you just want to open up a predrilled hole?
If you need to go more than .010-.020 " (more than a reamer can
handle)
you should get a core drill.It's a cross between a drill and a reamer.
No cutting point, 3 to 4 flute
and will leave you with a straight and smooth hole.
http://en.wikipedia.org/wiki/Drill_bit
Scroll down to core drill.
Clay

"woodworker88" wrote in message
...
I've recently noticed a problem with drilling in steel that I want
to
ask the group's opinion on. The problem is the drill grabbing in
the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off
more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a
full-diameter
hole in the same material, same setup, etc. The drill bits are
brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds
and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but
this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers
into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other
purpose.
I can't actually try using them since the proper sized drill from
that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

woodworker88 wrote:
I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

How's your freehand grinding skills? What's the requirement for precision?

You could grind your own bullet point on the drill bit, to suit the
existing hole, or you could grind a pilot on the nose of the drill.

Pretty common thing to find on an aircraft sheet metal guy's bench.

You can save yourself a lot of time that would be spend dickin' around
with chipbreakers, by adjusting the rake of the cutting edge. Most
often, the rake is too much, and adjusting it to cut a little more of a
scraping action, will slow down the "bite" that it takes. When cutting
brass, the edge gets a flat that is parrallel to the axis of the drill,
effectively making a zero rake angle. You can adjust between the
originall angle, and zero as cutting dictates.

Easier than that, though, is to arrange to have a piece of similar
material behind the workpiece, so that the cut proceeds through the work
without having to deal with the lips digging in.


Some ideas, anyways. Use the ones that you feel will work for you.

My life is too short to be muckin about trying to grind matching
grooves on drill lips.

Cheers
Trevor Jones

On Thu, 13 Dec 2007 21:39:43 -0800 (PST), woodworker88
wrote:

I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88


This is a pretty common problem, even when drilling soft metals like
aluminum. Simply grind a very small flat along the cutting edge of the
drill so that the sharp edge formed by the flute and the end of the
drill is made a narrow flat parallel with a center line drawn through
the length of the drill.









Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Grind the cutting edge flat for zero rake as Bruce suggests will tame
those large drills fine. Works well in the harder steels too.

Your problem is the lathe, not the drill bit. The only way this can occur is
if the holding chuck of spindle has fore aft play or play exists in the tail
stock allowing the drill chuck to jump into the work. If you are using the
correct MT drill chuck mount, it will have a tang on the end to prevent this
rotation. Repair the lathe by removing the play and leave the drill bit
alone.
Steve

"woodworker88" wrote in message
...
I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

On Sat, 15 Dec 2007 10:04:00 +0100, "Steve Lusardi"
wrote:

Your problem is the lathe, not the drill bit. The only way this can occur is
if the holding chuck of spindle has fore aft play or play exists in the tail
stock allowing the drill chuck to jump into the work. If you are using the
correct MT drill chuck mount, it will have a tang on the end to prevent this
rotation. Repair the lathe by removing the play and leave the drill bit
alone.
Steve

"woodworker88" wrote in message
...
I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

What is happening is that the rake on the cutting edge of the drill is
actually digging into the bottom of the hole and pulling the drill bit
into the material being drilled. If there is only a taper to oppose
this "pulling" then the chuck or drill bit will be pulled out of the
tail stock.

This is not at all uncommon when drilling soft materials or using a
large pilot drill.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Bruce,
That can only happen if your tapers are worn out/ not locking properly. Of
course this does happen in a mill, but you have draw bars to counter that.
It should never happen in a lathe, because the forces are not high enough.
If it does, the most likely culprit is excessive back lash in the tailstock
screw. This tendency can be somewhat countered by tightening the tailstock
spindle drag/ lock lever. Abusing the grind on a drill bit is a bandaid, not
a cure.
Steve

"Bruce in Bangkok" wrote in message
...
On Sat, 15 Dec 2007 10:04:00 +0100, "Steve Lusardi"
wrote:

Your problem is the lathe, not the drill bit. The only way this can occur
is
if the holding chuck of spindle has fore aft play or play exists in the
tail
stock allowing the drill chuck to jump into the work. If you are using the
correct MT drill chuck mount, it will have a tang on the end to prevent
this
rotation. Repair the lathe by removing the play and leave the drill bit
alone.
Steve

"woodworker88" wrote in message
...
I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

What is happening is that the rake on the cutting edge of the drill is
actually digging into the bottom of the hole and pulling the drill bit
into the material being drilled. If there is only a taper to oppose
this "pulling" then the chuck or drill bit will be pulled out of the
tail stock.

This is not at all uncommon when drilling soft materials or using a
large pilot drill.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

"Steve Lusardi" wrote in message
...
Bruce,
That can only happen if your tapers are worn out/ not locking properly. Of
course this does happen in a mill, but you have draw bars to counter that.
It should never happen in a lathe, because the forces are not high enough.
If it does, the most likely culprit is excessive back lash in the
tailstock screw. This tendency can be somewhat countered by tightening the
tailstock spindle drag/ lock lever. Abusing the grind on a drill bit is a
bandaid, not a cure.
Steve



the key thing you added, above, was "drawbar" - OP doesn't seem to have
one - adding a drawbar might solve the problem, but most metal lathes I'm
familiar with don't have a way to add a drawbar to the tailstock. Boring
rather than drilling will also fix it



--
Posted via a free Usenet account from http://www.teranews.com

Got it. I have used zero rake (or at least minimal rake) drills
before in sheet metal and have had good sucess. I believe that those
will work well. That small change shouldn't be difficult to make with
my bench grinder.

I have read about core drills, and undoubtably they are the best way
to go, but out of my budget for the few jobs that need it. Modifying
an existing drill seems like the ideal solution.

About my lathe--while my tailstock taper and associated parts do need
a bit of work (it is a 60+ year old lathe, with the original drill
chuck shank), it's more than that. The fact is that I can visually
see the drill bit taking an excessive chip. If it weren't the taper
slipping, something else would give instead.

Thanks to everyone for their comments. I'll let everyone know how the
project turns out.

On Dec 14, 5:20 am, Bruce in Bangkok wrote:
On Thu, 13 Dec 2007 21:39:43 -0800 (PST), woodworker88



This is a pretty common problem, even when drilling soft metals like
aluminum. Simply grind a very small flat along the cutting edge of the
drill so that the sharp edge formed by the flute and the end of the
drill is made a narrow flat parallel with a center line drawn through
the length of the drill.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Sat, 15 Dec 2007 15:19:40 +0100, "Steve Lusardi"
wrote:

Bruce,
That can only happen if your tapers are worn out/ not locking properly. Of
course this does happen in a mill, but you have draw bars to counter that.
It should never happen in a lathe, because the forces are not high enough.
If it does, the most likely culprit is excessive back lash in the tailstock
screw. This tendency can be somewhat countered by tightening the tailstock
spindle drag/ lock lever. Abusing the grind on a drill bit is a bandaid, not
a cure.
Steve

Top posted to continue the sequence of messages.

Sorry but you are wrong about a taper holding, come rain or come
shine. I have had taper shank tools fall out of hand drill presses,
radial drills, vertical mills and lathes due either to chatter or the
rake pulling the drill into the work faster then the feed rate. That
is the reason vertical milling machines almost always incorporate a
draw bar - to hold the taper shank tool in place.

To illustrate the forces involved try this. Drill a 7/16" hole in a
piece of 1/8" thick commercially pure aluminum using an air or
electric powered hand drill. Now change to a 1/2" drill and try to
enlarge the existing 7/16" hole to 1/2" through only half the
thickness of the aluminum. Odds aren't that you won't be able to do it
(at least not without considerable practice) as the rake angle digs in
and pulls the drill into the metal with considerable force.

Finally a drill is just another cutter and rake and clearance angles
are determined by the material being cut, cutting speed and the
condition of the machine being used.


"Bruce in Bangkok" wrote in message
.. .
On Sat, 15 Dec 2007 10:04:00 +0100, "Steve Lusardi"
wrote:

Your problem is the lathe, not the drill bit. The only way this can occur
is
if the holding chuck of spindle has fore aft play or play exists in the
tail
stock allowing the drill chuck to jump into the work. If you are using the
correct MT drill chuck mount, it will have a tang on the end to prevent
this
rotation. Repair the lathe by removing the play and leave the drill bit
alone.
Steve

"woodworker88" wrote in message
...
I've recently noticed a problem with drilling in steel that I want to
ask the group's opinion on. The problem is the drill grabbing in the
hole, and it only happens in one situation (unfortunately, a common
one). The problem happens when I try to drill out an existing hole
which is larger than the web of the larger drill, which you should
avoid when choosing pilot drills, but in which I often don't get a
choice (if it's modifying an existing part). Since the web of the
drill does not regulate drill feed, the drill tends to "bite off more
than it can chew", take a large chip, and bind. This happens most
often when drilling in the lathe, and tends to spin the drill chuck
rather violently in the tailstock taper. I know this isn't just a
general taper issue, since it works fine when drilling a full-diameter
hole in the same material, same setup, etc. The drill bits are brand
new, very sharp American drill bits in the 3/8"-1/2" size. Feeds and
speeds, etc are not the issue, nor is the material any more unusual
than mild steel. The primary machine is a 12x36 Atlas lathe, but this
has happened in other machines in the past as well.

My main question is about chipbreakers. When dealing with cutters
that tend to "bite off more than they can chew", such as parting
tools, I have had good success grinding appropriate chipbreakers into
the top edges. Since I can visually confirm that the binding is due
to the taking of an inappropriately large chip by the drill cutting
edges, it would seem that this is an ideal solution. However, where
would I go about grinding a chipbreaker into the cutting edge of a
drill? I do have a set of drill bits with small vee grooves factory
ground perpendicular to the middle of each cutting lip, but I don't
recall if they were advertised as chipbreakers or some other purpose.
I can't actually try using them since the proper sized drill from that
set has long since been reground normally in the course of normal
sharpening.

My question is whether or not grinding such a groove into a normal
drillbit would solve the problem and, if not, if there are any other
suggestions that people have to solve the problem?

Thanks in advance,
woodworker88

What is happening is that the rake on the cutting edge of the drill is
actually digging into the bottom of the hole and pulling the drill bit
into the material being drilled. If there is only a taper to oppose
this "pulling" then the chuck or drill bit will be pulled out of the
tail stock.

This is not at all uncommon when drilling soft materials or using a
large pilot drill.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Sat, 15 Dec 2007 11:20:01 -0800 (PST), woodworker88
wrote:

Got it. I have used zero rake (or at least minimal rake) drills
before in sheet metal and have had good sucess. I believe that those
will work well. That small change shouldn't be difficult to make with
my bench grinder.

I have read about core drills, and undoubtably they are the best way
to go, but out of my budget for the few jobs that need it. Modifying
an existing drill seems like the ideal solution.

About my lathe--while my tailstock taper and associated parts do need
a bit of work (it is a 60+ year old lathe, with the original drill
chuck shank), it's more than that. The fact is that I can visually
see the drill bit taking an excessive chip. If it weren't the taper
slipping, something else would give instead.

Thanks to everyone for their comments. I'll let everyone know how the
project turns out.

Just a small comment. You probably don't need to grind a very wide
flat on the cutting edge. Then when you are finished with ther project
it is not a big job to regrind the drill to return it to the normal
rake angle.


On Dec 14, 5:20 am, Bruce in Bangkok wrote:
On Thu, 13 Dec 2007 21:39:43 -0800 (PST), woodworker88



This is a pretty common problem, even when drilling soft metals like
aluminum. Simply grind a very small flat along the cutting edge of the
drill so that the sharp edge formed by the flute and the end of the
drill is made a narrow flat parallel with a center line drawn through
the length of the drill.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Dec 15, 2:20 pm, woodworker88 wrote:
.....
About my lathe--while my tailstock taper and associated parts do need
a bit of work (it is a 60+ year old lathe, with the original drill
chuck shank), it's more than that. The fact is that I can visually
see the drill bit taking an excessive chip.

I have the same problem with my 40+ year old lathe, but only with some
combinations of feed pressure and size ratio. Simply switching to a
different size drill bit usually fixes it. I get good results opening
up the hole in 1/4" steps and then feeding the final bit which may be
removing only 1/16" quite slowly. For some reason taper shank bits
work better for me than a chuck. Maybe having less rotational inertia
they don't amplify slight chattering.

Jim Wilkins

Okay, will do.

I have a few taper shank drills, but I hardly ever use them anymore
because the were cheap imports (all I could afford), and the American
straight shank drills I bought at a closeout sale of a machine tool
supply store cut so much better, it far outweighs (at least as far as
I can tell) any advantages of my particular taper shank drills. Now
if only I had...

On Dec 15, 5:52 pm, Bruce in Bangkok wrote:

Just a small comment. You probably don't need to grind a very wide
flat on the cutting edge. Then when you are finished with ther project
it is not a big job to regrind the drill to return it to the normal
rake angle.