Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

What's the experience in using these items and what's the
reasoning behind the design differences?

Jim



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wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

What's the experience in using these items and what's the
reasoning behind the design differences?

Jim

You can get spotting drills in both 90º and 120º angles.
The main advantage is the robustness of the drill.
Longevity far outweighs the cost especially using TIN
coated spotting drills. I love em! :-)

Tom

wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

I use them a lot on the mill, seldomn on the lathe. I like them!
The keep long, because you won't drill deep holes, and you can't and
should not drill holes. Just the conical part.
Mine are two-fluted.
Buy them!


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO // Eigenbau-Digitalanzeige
http://www.yadro.de

In article , Nick Müller
writes
wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

I use them a lot on the mill, seldomn on the lathe. I like them!
The keep long, because you won't drill deep holes, and you can't and
should not drill holes. Just the conical part.
Mine are two-fluted.
Buy them!

I have never used a spotting drill - and don't know what their
construction is. However, just an alternative idea for pentagrid: have
you tried stub drills. I almost always use these for starting holes,
especially in small sizes. They are about half the length of a normal
jobbers drill bit, and hence much stiffer, but only cost about the same
or a little more. I do often spot with the very tip of a centre drill,
but I'm not sure it is necessary.

David
--
David Littlewood

You can buy whole drill sets (w/ the case) in the stub length, even the 115
pc set. A little pricey, tho.
Stub drills can often save you a tool change, altho I'm sure the purists out
there are clenching and grinding their teeth.
The silver lining to breaking a jobber's length: Now you got a stubby!
--
Mr. P.V.'d
formerly Droll Troll
"David Littlewood" wrote in message
news
In article , Nick Müller
writes
wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

I use them a lot on the mill, seldomn on the lathe. I like them!
The keep long, because you won't drill deep holes, and you can't and
should not drill holes. Just the conical part.
Mine are two-fluted.
Buy them!

I have never used a spotting drill - and don't know what their
construction is. However, just an alternative idea for pentagrid: have you
tried stub drills. I almost always use these for starting holes,
especially in small sizes. They are about half the length of a normal
jobbers drill bit, and hence much stiffer, but only cost about the same or
a little more. I do often spot with the very tip of a centre drill, but
I'm not sure it is necessary.

David
--
David Littlewood

"David Littlewood" wrote in message
news
In article , Nick Müller
writes
wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

I use them a lot on the mill, seldomn on the lathe. I like them!
The keep long, because you won't drill deep holes, and you can't and
should not drill holes. Just the conical part.
Mine are two-fluted.
Buy them!

I have never used a spotting drill - and don't know what their
construction is. However, just an alternative idea for pentagrid: have
you tried stub drills. I almost always use these for starting holes,
especially in small sizes. They are about half the length of a normal
jobbers drill bit, and hence much stiffer, but only cost about the same
or a little more. I do often spot with the very tip of a centre drill,
but I'm not sure it is necessary.

David
--
David Littlewood

What David said, but insist in a split point to insure free cutting without
deflection. The web of a drill has extreme negative rake and doesn't
cut worth a damn. By splitting the point, the negative rake is eliminated,
replaced by a cutting edge that cuts instead of plows. The difference
in starting and drilling is remarkable.

Folks that came up in the shop the old way did *not* routinely use spotting
drills. That's what center drills were for, along with actually drilling
centers. Don't ask me how I know this-----it's hard enough getting old
without someone bringing it to your attention.

Spotting drills are really a tool of the CNC age, where it's important to
have a device that will start a hole where it's desired and not worry about
breaking the tip off, which is common in center drill use, particularly when
you get down to a #1 or smaller. By virtue of the grind design, spotting
drills have virtually no web, so they behave much like a split point drill.
Their short length provides rigidity and insures that the hole you drill
will be where desired, and the grind permits easy evacuation of the chips
that are generated. The tip is far more robust than that of a small center
drill.

Because of my training, and the era in which I spent my time in commercial
shops, I do not use them, nor have I ever.

Harold

On Wed, 22 Mar 2006 22:48:23 +0000, wrote:

Centre drill are often used as spotting drills in the lathe
but there's a pretty wild mismatch between center drill point
angles and the the usual jobber drill that follows. Special
spotting drills are produced for NC use at about three times the
price of similar centre drills.

How do the special features work and are they worth the
premium price? Some seem to be single flute designs and the
included angle is usually less thqn 118 deg jobber drill angle.

What's the experience in using these items and what's the
reasoning behind the design differences?


As others have said, I like spotting drills a lot. I use them in a
variety of CNC machines - mills, lathes, and screw machines. I used
to pay the big bucks for expensive NC spot drills, but I recently
ordered a few 3/16" NC spot drills from Western Cutting Tool for $3.86
each. They actually look pretty good, and I have had no problems with
them.

--
Bryce

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"David Littlewood"
wrote in message
news
In article
, Nick
Müller writes
wrote:

Centre drill are often used as spotting
drills in the lathe
but there's a pretty wild mismatch between
center drill point
angles and the the usual jobber drill that
follows. Special
spotting drills are produced for NC use at
about three times the
price of similar centre drills.

How do the special features work and are
they worth the
premium price? Some seem to be single flute
designs and the
included angle is usually less thqn 118 deg
jobber drill angle.

I use them a lot on the mill, seldomn on the
lathe. I like them!
The keep long, because you won't drill deep
holes, and you can't and
should not drill holes. Just the conical part.
Mine are two-fluted.
Buy them!

I have never used a spotting drill - and don't
know what their construction is. However, just
an alternative idea for pentagrid: have you
tried stub drills. I almost always use these for
starting holes, especially in small sizes. They
are about half the length of a normal jobbers
drill bit, and hence much stiffer, but only cost
about the same or a little more. I do often spot
with the very tip of a centre drill, but I'm not
sure it is necessary.

David
--
David Littlewood

I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!

In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

AWEM

In article , Andrew Mawson
writes

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

AWEM


Thanks.

David
--
David Littlewood

Keywords:
In article , "Andrew Mawson" wrote:

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!

Sheet metal drills?

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

I've been looking for a supplier for these for decades, ever since I
tried some a friends father had. None of the drill vendors I've spoken
to have even heard of them. I even checked with several of the major US
manufacturers at the Eastech machine tool show a few years back.

Doug White

edge at the periphery of the flutes

I've been looking for a supplier for these for
decades, ever since I
tried some a friends father had. None of the
drill vendors I've spoken
to have even heard of them. I even checked with
several of the major US
manufacturers at the Eastech machine tool show a
few years back.

Doug White

Plenty of them here in Auz

Andrew Mawson wrote:


"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

Are spot-weld removing drills the same?

Lots of them on ebay (spot, drill).


--
Peter Fairbrother

"Peter Fairbrother" wrote in message
...
Andrew Mawson wrote:


"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

Are spot-weld removing drills the same?

Lots of them on ebay (spot, drill).


Black and Decker do the sort of drills Andrew is describing, under the
Piranha name. They work well in sheet metal (at least up to about 10mm) but
are expensive. Our workshop guys at work call them crown-point drills.
They are similar to the lip and spur drills used by woodworkers. Same basic
idea - cut the rim of the hole before removing all of the support.

In message , Andrew Mawson
writes

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

AWEM




Perhaps look at .............

http://www.centerdrills.com/CNCspot.htm



Mike
--
Mike Whittome - Frequently wrong; seldom without opinion!

Mike Whittome wrote:

In message , Andrew Mawson
writes

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

AWEM




Perhaps look at .............

http://www.centerdrills.com/CNCspot.htm

After reading this thread I bought some spotting drills to try (from ebay),
and I have only one comment - wonderful!!

Centre drills are good for drilling centers where you need a pilot hole and
a 60 degree "countersink" for the center, but for getting a hole in the
right place without hassles or the drill bit wandering all over, spotting
drills are unbeatable.

I just drilled a cross hole in a bit of hard shiny 8mm round stainless with
a rickety old pillar drill, and I didn't even use a centre pop to mark it -
nae fuss nor bother, and it just started in the right place!

I don't know how they work, because they don't look too different, but I am
convinced - apart from centers, I'll never use a centre drill to start a
hole again.



OT, how does one spell the word? Is it optional, or another case of two
countries divided by a common language?

--
Peter Fairbrother

On Fri, 28 Apr 2006 01:03:01 +0100, Peter Fairbrother
wrote:

Mike Whittome wrote:

In message , Andrew Mawson
writes

"David Littlewood" wrote in message
...
In article , Tom Miller
writes


I tend to use sheet metal drills for hole
starting. They are very short and are double
ended. you can break twice as many for the same
price!


Sheet metal drills?

David
--
David Littlewood

They are ground to a sort of a cusp - centre point and also cutting
edge at the periphery of the flutes

AWEM




Perhaps look at .............

http://www.centerdrills.com/CNCspot.htm

After reading this thread I bought some spotting drills to try (from ebay),
and I have only one comment - wonderful!!

Centre drills are good for drilling centers where you need a pilot hole and
a 60 degree "countersink" for the center, but for getting a hole in the
right place without hassles or the drill bit wandering all over, spotting
drills are unbeatable.

I just drilled a cross hole in a bit of hard shiny 8mm round stainless with
a rickety old pillar drill, and I didn't even use a centre pop to mark it -
nae fuss nor bother, and it just started in the right place!

I don't know how they work, because they don't look too different, but I am
convinced - apart from centers, I'll never use a centre drill to start a
hole again.



OT, how does one spell the word? Is it optional, or another case of two
countries divided by a common language?
You spell centre, I spell center. You say tomato, I say tomato. It all
works. I do find it interesting that so many words, and so many
accents, that should be the same are so different after a couple
hundred years. Even though we have been talking to each other the
entire time. Not just England and the USA. England, Australia, Canada,
and the USA. All different. And across each country big differences.
Not just class differences in the way we speak, but even in the same
class. Blue collar workers sound much different in different parts of
the country even though they use much of the same slang.
ERS

"Peter Fairbrother" wrote in message
...
snip----

I don't know how they work, because they don't look too different, but I
am
convinced - apart from centers, I'll never use a centre drill to start a
hole again.

The one big difference is rake angle. Center drills are zero rake, do not
cut to center, and have little chip relief. Those conditions do not lend
themselves to easy machining.

Harold

In rec.crafts.metalworking Harold and Susan Vordos wrote:
The one big difference is rake angle. Center drills are zero rake, do not
cut to center, and have little chip relief. Those conditions do not lend
themselves to easy machining.
--Soooo they're good for thin materials but not for drilling to
depth?


--
"Steamboat Ed" Haas : I'll have the roast duck
Hacking the Trailing Edge! : with the mango salsa...
www.nmpproducts.com
---Decks a-wash in a sea of words---