Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest

"Bernard Arnest" wrote in message
ups.com...
Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest

Drill press? Way too slow, 1,200 rpm min. drill a few seconds ease-up let
the coolant flow down dill a few seconds and so on. Sharp, good bits a
must! Learn to sharpen them by hand, the girls think it's cool.

On 24 Apr 2006 23:14:27 -0700, "Bernard Arnest"
wrote:

Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest

You can't have too much coolant. 300 RPM is quite slow for such a
small drill so you're OK on speed. You probably are not feeding
aggressively enough to avoid rubbing a hard spot in the hole. Lean on
the quill a bit harder, keep that chip going. You want your curly
chip to be more than a shaving.

On 24 Apr 2006 23:14:27 -0700, "Bernard Arnest"
wrote:

Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest


Welcome to the wonderful and wacky world of Stainless Steel.

The Machinability Index of 310 is similar to 304

Little shop mantra to remember

"304, shes a whore, 303..shes for me"


Gunner

"I think this is because of your belief in biological Marxism.
As a genetic communist you feel that noticing behavioural
patterns relating to race would cause a conflict with your belief
in biological Marxism." Big Pete, famous Usenet Racist

In article . com,
"Bernard Arnest" wrote:

curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try

Stainless steel (in general, and some grades in particular, 310 among
them judging by other replies) has the nasty behavior of work hardening
as you cut it. Thus, you cannot take light cuts and get away with it.
Odds are, you are not applying _nearly_ enough feed pressure. If the
chips are not heavy and substantial (making you want a pair of gloves on
to remove them, lest they slice your hand open) you're not cutting hard
enough. Likewise, when you cut it on a lathe, you have to take a fairly
heavy cut, or you'll take no cut at all.

Harder drills can help some, if you happen to be using a "regular drill
bit", but technique is key with stainless - maintain pressure, or back
the drill right out, and when restarting, maintain pressure - do not
"ease" into (or out of) the cut or at any time cut lightly, or the
cutting face hardens up, dulls the bit, and hardens some more.

--
Cats, coffee, chocolate...vices to live by

--What they all said and don't forget to chamfer the lip of the hole
before you start tapping it. Use a good tap lube too; I'd suggest "Moly
Dee". Also you shouldn't need to tap the hole the entire 1/2" depth to get
good thread engagement.

--
"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---

In article . com, Bernard
Arnest says...

thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?

1) you are probably feeding to slow. The material is work
hardening.

2) the speed is about right, if a tad on the slow side.

3) you are using poor quality drills. Get a high cobalt alloy
drill and things will go better. You were probably using
plain hss or carbon steel.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On Tue, 25 Apr 2006 01:43:44 -0500, Don Foreman
wrote:

On 24 Apr 2006 23:14:27 -0700, "Bernard Arnest"
wrote:

Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest

You can't have too much coolant. 300 RPM is quite slow for such a
small drill so you're OK on speed. You probably are not feeding
aggressively enough to avoid rubbing a hard spot in the hole. Lean on
the quill a bit harder, keep that chip going. You want your curly
chip to be more than a shaving.

Afterthought: since you're in learning mode (we all are!), consider
getting a couple of #36 or #35 drills and scraps of 310, and see just
how hard you can lean on them before a drill snaps. This'll give you
a feel for how much axial force you can prudently use, with no
cursing or frustration involved. Might be among the best 2 bux
you ever spent.

6-32 is probably the most fragile tap made. I hate 'em. I'd drill
your holes at least one size oversize -- #35 -- for tapping 310.

Tom Gardner wrote:


must! Learn to sharpen them by hand, the girls think it's cool.

Only in Cleveland (:

"Jim Stewart" wrote in message
...
Tom Gardner wrote:


must! Learn to sharpen them by hand, the girls think it's cool.

Only in Cleveland (:


Works for me!

"Tom Gardner" wrote in message
. net...
sninp------

Drill press? Way too slow, 1,200 rpm min. drill a few seconds ease-up
let
the coolant flow down dill a few seconds and so on. Sharp, good bits a
must! Learn to sharpen them by hand, the girls think it's cool.

Shame on you, Tom. That speed in stainless is a sure recipe for failure.
500 RPM could be too fast.

Keep the tool sharp, don't let it idle---and don't run too fast. Stainless
work hardens quickly----and what you described is exactly that---work
hardened. If you look carefully at your drill, you'll find it's well worn
at the margins, and is now drilling a tapered hole, or trying to. The
drill, in order to be restored to being useful, will have to be pushed back
until the margin is not altered. Could be as much as 1/8", depending on how
long you leaned on the drill. You heard the sound of a drill grabbing and
then slipping fairly rapidly. That's the nature of stainless.

If you have choices, do as Gunner said, use 303. Se is the best to use, but
S is very acceptable. Each is slightly lower in corrosion resistance, but
the difference in machining is huge. If you can use a 400 series, 416 is
even better. It's heat treatable, and is the best machining of all the
stainless family.

Harold

That's a mighty small bit Harold, but in retrospect, I wasn't thinking.
That stuff does work harden easily. And most of my experience is with 302.


"Harold and Susan Vordos" wrote in message
...

"Tom Gardner" wrote in message
. net...
sninp------

Drill press? Way too slow, 1,200 rpm min. drill a few seconds ease-up
let
the coolant flow down dill a few seconds and so on. Sharp, good bits a
must! Learn to sharpen them by hand, the girls think it's cool.

Shame on you, Tom. That speed in stainless is a sure recipe for
failure.
500 RPM could be too fast.

Keep the tool sharp, don't let it idle---and don't run too fast.
Stainless
work hardens quickly----and what you described is exactly that---work
hardened. If you look carefully at your drill, you'll find it's well
worn
at the margins, and is now drilling a tapered hole, or trying to. The
drill, in order to be restored to being useful, will have to be pushed
back
until the margin is not altered. Could be as much as 1/8", depending on
how
long you leaned on the drill. You heard the sound of a drill grabbing and
then slipping fairly rapidly. That's the nature of stainless.

If you have choices, do as Gunner said, use 303. Se is the best to use,
but
S is very acceptable. Each is slightly lower in corrosion resistance, but
the difference in machining is huge. If you can use a 400 series, 416 is
even better. It's heat treatable, and is the best machining of all the
stainless family.

Harold

....but you had to like my "hand sharpening drills gets the girls" thing.
Susan considers that your finest attribute.

If I did the math right, your 300 RPM translates into about 10 surface feet
per minute.

If you use a 50 SFM as a starting point, the RPM should be around 1500 RPM.

At 300 RPM, you are rubbing the drill bit to death. (eventually) Especially
when going 3/4 deep.
Increased RPM should show a vast improvement.

Good luck!

"Bernard Arnest" wrote in message
ups.com...
Hi,
I'm new to machining, so maybe it's a tyro's silly error, but here's
the situation:

I was drilling 3/4" deep into 310 stainless for a 6-32 tap. I forget
the drill size, but for a 6-32 screw to thread into it, not very large;
something over 1/8" I was going at 300 rpm with a HSS bit. I used
adequate oil and coolant, maybe too much if there even can be too much.
Usually you can feel if it's going right; apply a fair amount of
pressure, enough to feel it sink slowly into the material and see long,
curly shavings. The first hole went fine. Halfway through the second,
however, it made a quite audible rubbing sound and with nigh-dead
progress spewed tiny flakes of metal instead of long, even curls. I
pulled out the bit and saw that it was quite dull. I decided to try
again, in case it was somewhat dull to begin with. The shop instructor
handed me what he concluded was a fairly new, sharp bit. The same
thing happened again; after little over a linear inch of successful
drilling, it went dull. What am I doing wrong?


thank you for the advice,
-Bernard Arnest

"Tom Gardner" wrote in message
. net...
...but you had to like my "hand sharpening drills gets the girls" thing.
Susan considers that your finest attribute.


Hard to argue with that!

Hey-------wait a damned minute.

How do you know what Susan likes?

I'm gonna have to keep an eye on you two.

H

On Wed, 26 Apr 2006 11:40:23 -0700, Harold and Susan Vordos wrote:

"Tom Gardner" wrote in message
. net...
...but you had to like my "hand sharpening drills gets the girls" thing.
Susan considers that your finest attribute.

Hey-------wait a damned minute.
How do you know what Susan likes?

C'mon, man, we _all_ know what Susan likes.

I'm gonna have to keep an eye on you two.

(Oh good, he only knows about two...)

"Ace" wrote in message
...
If I did the math right, your 300 RPM translates into about 10 surface
feet per minute.

If you use a 50 SFM as a starting point, the RPM should be around 1500
RPM.

At 300 RPM, you are rubbing the drill bit to death. (eventually)
Especially when going 3/4 deep.
Increased RPM should show a vast improvement.

Good luck!

I feel somewhat vindicated! (Where do I send your check?)

On Tue, 25 Apr 2006 17:02:57 -0700, Harold and Susan Vordos wrote:

Keep the tool sharp, don't let it idle---and don't run too fast.
Stainless work hardens quickly----and what you described is exactly
that---work hardened.
snip

Harold
This is good advice. Learn what work-hardening is - some machinists think
it has something to do with heat-it does not. I would only add that I
think a drill with a fat chisel point is the worst for this type of
stainless because chisel points work-harden the material. Use or make one
with a split point. When tapping, a high pressure lube like Moly-dee is
beneficial, IMHO. Brent.

"Brent Muller" wrote in message
newsan.2006.04.30.05.46.15.207122@SPAMSPAMEGGSAN DSPAMvelocitus.net...
On Tue, 25 Apr 2006 17:02:57 -0700, Harold and Susan Vordos wrote:

Keep the tool sharp, don't let it idle---and don't run too fast.
Stainless work hardens quickly----and what you described is exactly
that---work hardened.
snip

Harold
This is good advice. Learn what work-hardening is - some machinists think
it has something to do with heat-it does not.

Correct! You want a good example? Buck a stainless rivet, even one made
from 303 S, for a prolonged period of time, then check the hardness of the
head with a file. Make the file an old, useless one, for the teeth will
be instantly dulled where they contact the rivet head. Heat plays no role
in work hardening----although heat may be generated in the process, and
probably is.

I would only add that I
think a drill with a fat chisel point is the worst for this type of
stainless because chisel points work-harden the material. Use or make one
with a split point. When tapping, a high pressure lube like Moly-dee is
beneficial, IMHO. Brent.

Yep, that's right, too. The chisel point of a drill is extreme negative
rake, so it doesn't cut, it displaces. Cold working stainless is a quick
recipe for work hardening, and that's what you're doing when you drill with
a conventionally sharpened drill. A thinned web, or a split point is often
the solution to the problem of work hardening, but the toughness of
stainless is correspondingly hard on split points, so one must achieve a
delicate balance of cutting edge design to achieve longevity of cutting
tools and cut without hardening. Needless to say, a one-off project
wouldn't be as critical as a production run.

Harold

In article , Harold and Susan Vordos says...

... The chisel point of a drill is extreme negative
rake, so it doesn't cut, it displaces. Cold working stainless is a quick
recipe for work hardening, and that's what you're doing when you drill with
a conventionally sharpened drill. A thinned web, or a split point is often
the solution to the problem of work hardening, but the toughness of
stainless is correspondingly hard on split points, so one must achieve a
delicate balance of cutting edge design to achieve longevity of cutting
tools and cut without hardening. Needless to say, a one-off project
wouldn't be as critical as a production run.

I have a favorite saying, good tool steel isn't cheap.

The way out of the problem is to use a high cobalt drill, from a
reputable manufacturer. Then do all the details right:

1) drill a pilot hole so the larger drill's dead center doesn't have
to cut.

2) keep the feed rate up so the work is not tempted to work-harden.

3) use a suitable cutting fluid.

4) choose the correct sfpm for the drill so the edge does not
break down from being run too fast.

Aside from work-hardening, stainless steels exhibit a very low
thermal conductivity. This is the reason that sfpm numbers like
one would use for carbon steels will put a drill out of action
in stainless, rapidly. Noplace for the heat to go.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 30 Apr 2006 12:42:46 -0700, jim rozen
wrote:

In article , Harold and Susan Vordos says...

... The chisel point of a drill is extreme negative
rake, so it doesn't cut, it displaces. Cold working stainless is a quick
recipe for work hardening, and that's what you're doing when you drill with
a conventionally sharpened drill. A thinned web, or a split point is often
the solution to the problem of work hardening, but the toughness of
stainless is correspondingly hard on split points, so one must achieve a
delicate balance of cutting edge design to achieve longevity of cutting
tools and cut without hardening. Needless to say, a one-off project
wouldn't be as critical as a production run.

I have a favorite saying, good tool steel isn't cheap.

The way out of the problem is to use a high cobalt drill, from a
reputable manufacturer. Then do all the details right:

1) drill a pilot hole so the larger drill's dead center doesn't have
to cut.

2) keep the feed rate up so the work is not tempted to work-harden.

3) use a suitable cutting fluid.

4) choose the correct sfpm for the drill so the edge does not
break down from being run too fast.

Aside from work-hardening, stainless steels exhibit a very low
thermal conductivity. This is the reason that sfpm numbers like
one would use for carbon steels will put a drill out of action
in stainless, rapidly. Noplace for the heat to go.

Jim
Not only that but SS sticks to the cutting tool. As it comes off it
will pull particles out of the cutting tool which makes it dull fast.
The less time you can keep the drill in contact with the work the
better.
ERS

According to jim rozen :
In article , Harold and Susan Vordos says...

... The chisel point of a drill is extreme negative
rake, so it doesn't cut, it displaces. Cold working stainless is a quick
recipe for work hardening, and that's what you're doing when you drill with
a conventionally sharpened drill. A thinned web, or a split point is often
the solution to the problem of work hardening, but the toughness of
stainless is correspondingly hard on split points, so one must achieve a
delicate balance of cutting edge design to achieve longevity of cutting
tools and cut without hardening. Needless to say, a one-off project
wouldn't be as critical as a production run.

I have a favorite saying, good tool steel isn't cheap.

The way out of the problem is to use a high cobalt drill, from a
reputable manufacturer. Then do all the details right:

1) drill a pilot hole so the larger drill's dead center doesn't have
to cut.

Thus transferring the primary problem to the pilot hole drill,
instead. :-) (Granted, it is easier to maintain sufficient pressure on a
smaller drill bit, unless you have proper power feed.)

And a split point should eliminate the need fro the pilot hole,
as there is no dead center.

However, larger split point bits of good steel are more
expensive, so get several of the smaller split point high cobalt drill
bits (the same diameter as the web of the larger drill bit) and you can
use somewhat less expensive (and easier to sharpen) larger bits. It is
a lot easier to sharpen to a chisel point than to a split point, unless
you have special equipment for the purpose.

The rest (which I've snipped from below) was good advice anyway.

Good Luck,
DoN.
--
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