--Having a little problem with same. I'm trying to bore 2-3/4" dia
holes thru 2-1/2" thick 304 stainless; gotta do 4 parts. I managed to get
the pilot holes up to about .875" with available drillbits, then I switched
to a boring head and, moving in increments of 0.1" on diameter I got the
holes enlarged to about 1.2" but then suddenly it got reeeeal hard to cut,
even with a carbide tipped boring bar. Shallower cuts seem my only option
but at this rate it'll be winter B4 I get the holes finished! I'm going to
go see a pal with a honkin' big lathe who can speed things up a little bit
and that will solve the predicament.
--But I'm thinking *next* time I'll want to do something different
like use an endmill and a rotary table to hog out that kind of material,
then do a cleanup pass on my wimpy little lathe. I'm curious to know what
others have done in similar situations. Any ideas?

--
"Steamboat Ed" Haas : A human without a critter
Hacking the Trailing Edge! : is incomplete..
www.nmpproducts.com
---Decks a-wash in a sea of words---

All stainless will work harden. Some alloys more than others. (304 is easy) The general rule is to use a fast feed, low RPM and a
broad nose on the tool. Of course this assumes the lathe is stiff enough to handle the increased load. Small lathes makes these
jobs very difficult. My suggestion is to use M42 cobalt tools (8% Cobalt) and more tool relief angle to reduce tool drag. Carbide
cannot support the amount of relief required. Normal HSS isn't hard enough and all tools must be SHARP. Please also consider using
a cool mister. Anything to resist temperature rise also helps.
Steve

"steamer" wrote in message ...
--Having a little problem with same. I'm trying to bore 2-3/4" dia
holes thru 2-1/2" thick 304 stainless; gotta do 4 parts. I managed to get
the pilot holes up to about .875" with available drillbits, then I switched
to a boring head and, moving in increments of 0.1" on diameter I got the
holes enlarged to about 1.2" but then suddenly it got reeeeal hard to cut,
even with a carbide tipped boring bar. Shallower cuts seem my only option
but at this rate it'll be winter B4 I get the holes finished! I'm going to
go see a pal with a honkin' big lathe who can speed things up a little bit
and that will solve the predicament.
--But I'm thinking *next* time I'll want to do something different
like use an endmill and a rotary table to hog out that kind of material,
then do a cleanup pass on my wimpy little lathe. I'm curious to know what
others have done in similar situations. Any ideas?

--
"Steamboat Ed" Haas : A human without a critter
Hacking the Trailing Edge! : is incomplete..
www.nmpproducts.com
---Decks a-wash in a sea of words---

"steamer" wrote in t...
--Having a little problem with same. I'm trying to bore 2-3/4" dia
holes thru 2-1/2" thick 304 stainless; gotta do 4 parts. I managed to get
the pilot holes up to about .875" with available drillbits, then I switched
to a boring head and, moving in increments of 0.1" on diameter I got the
holes enlarged to about 1.2" but then suddenly it got reeeeal hard to cut,
even with a carbide tipped boring bar. Shallower cuts seem my only option
but at this rate it'll be winter B4 I get the holes finished! I'm going to
go see a pal with a honkin' big lathe who can speed things up a little bit
and that will solve the predicament.
--But I'm thinking *next* time I'll want to do something different
like use an endmill and a rotary table to hog out that kind of material,
then do a cleanup pass on my wimpy little lathe. I'm curious to know what
others have done in similar situations. Any ideas?


On Aug 20, 6:38*am, "Steve Lusardi" wrote:
All stainless will work harden. Some alloys more than others. (304 is easy) The general rule is to use a fast feed, low RPM and a
broad nose on the tool. Of course this assumes the lathe is stiff enough to handle the increased load. Small lathes makes these
jobs very difficult. My suggestion is to use M42 cobalt tools (8% Cobalt) and more tool relief angle to reduce tool drag. Carbide
cannot support the amount of relief required. Normal HSS isn't hard enough and all tools must be SHARP. Please also consider using
a cool mister. Anything to resist temperature rise also helps.

Not tried boring stainless myself but I was chatting to my dad
yesterday about pillar drills and he said that when he was drilling
stainless they had to up the motor size as stainless needs something
like 50% more feed pressure than free machining steel or the drill
rubs and burns out in no time at all - even if you have re-ground it
to around 130º angle etc - and of course the higher feed pressure
translates into more motor power required.

Druid

On Fri, 20 Aug 2010 07:38:59 +0200, "Steve Lusardi"
wrote:

All stainless will work harden. Some alloys more than others. (304 is easy) The general rule is to use a fast feed, low RPM and a
broad nose on the tool. Of course this assumes the lathe is stiff enough to handle the increased load. Small lathes makes these
jobs very difficult. My suggestion is to use M42 cobalt tools (8% Cobalt) and more tool relief angle to reduce tool drag. Carbide
cannot support the amount of relief required. Normal HSS isn't hard enough and all tools must be SHARP. Please also consider using
a cool mister. Anything to resist temperature rise also helps.
Steve

MACHINIST MATRA:
304 she's a whore, 303, she's for me.

If you can change material you'll save a ton o' grief. These are about
the same except you can't weld 303.

When I cut 304 on the Monarch 10EE, I'd set the feed at leat .005 and
take a miniumum cut of .025 even for the finish pass. Forget about a
spring pass. In back gear for more torque if over one inch. Slow
speeds. I use cutting oil on stainless. The only other job I use oil
on is threading.

On the Mazak M4 (20 hp gear head - 16,000 lb. machine) negative rake
carbide tooling and coolant will cut SS all day long. A big rigid
machine do help.

Karl Townsend wrote:
MACHINIST MATRA:
304 she's a whore, 303, she's for me.
--Heh I know the mantra and I'm afraid I'm stuck with 304 due to the
superior welding quality. After machining these 'sleeves' they have to be
welded to flanges.

When I cut 304 on the Monarch 10EE, I'd set the feed at leat .005 and
take a miniumum cut of .025 even for the finish pass. Forget about a
spring pass. In back gear for more torque if over one inch. Slow
speeds. I use cutting oil on stainless. The only other job I use oil
on is threading.
--I have lathe envy! I was trying to use a Myford Super 7B but the
problem is hanging onto the parts: using the outside jaws on the lathe I
could only hold about 3/8" of the end of the bar so I bored out soft jaws
and tried to use the mill instead. I've got a Criterion boring head but
beyond a certain diameter there just isn't enough horsepower in the
Bridgeport to keep the cut depth the same. Will try again today with
shallower depth of cut.

On the Mazak M4 (20 hp gear head - 16,000 lb. machine) negative rake
carbide tooling and coolant will cut SS all day long. A big rigid
machine do help.
--Negative rake tooling? So the cutter is, so to speak, dragging
across the cut? Hmmmm.

--
"Steamboat Ed" Haas : A human without a critter
Hacking the Trailing Edge! : is incomplete..
www.nmpproducts.com
---Decks a-wash in a sea of words---

Steve Lusardi wrote:
All stainless will work harden. Some alloys more than others. (304 is easy) The general rule is to use a fast feed, low RPM and a
broad nose on the tool. Of course this assumes the lathe is stiff enough to handle the increased load. Small lathes makes these
jobs very difficult. My suggestion is to use M42 cobalt tools (8% Cobalt)
and more tool relief angle to reduce tool drag.
--Yeah; a proper tool would probably help a lot. I'm using a stock
boring tool with a brazed on carbide that's pretty square-ish, so to speak.
will try grinding in a wee bit more relief angle.

Carbide cannot support the amount of relief required. Normal HSS isn't hard
enough and all tools must be SHARP.

Please also consider using a cool mister. Anything to resist temperature
rise also helps.
--Am using one; running it rich too. Mobil synthetic lube seems to
work pretty well.

--
"Steamboat Ed" Haas : A human without a critter
Hacking the Trailing Edge! : is incomplete..
www.nmpproducts.com
---Decks a-wash in a sea of words---