Chatter Problem
 

Hi guys. I'm trying to maching a small item on a lathe. It's going to be a
depth gauge, folloeing the directions givien the the Machinist's Bedside
Reader. The material is some sort of mild steel, pedigree unkonown. I have
ground a full radius tool from a peice of HSS. I have ground a 45 degree
cone on the end of the tool and a 10 degree rake (?) angle on the top
surface. I have tried speeds of 200 RPM to 1000 RPM.
The work piece is about .625 Dia. X 2.5 in long. Every time I try to
machine the OD I get a lot of chatter. Any ideas?
Thanks

Chatter Problem
 

"Kelly Jones" wrote in
:

Hi guys. I'm trying to maching a small item on a lathe. It's going to
be a depth gauge, folloeing the directions givien the the Machinist's
Bedside Reader. The material is some sort of mild steel, pedigree
unkonown. I have ground a full radius tool from a peice of HSS. I
have ground a 45 degree cone on the end of the tool and a 10 degree
rake (?) angle on the top surface. I have tried speeds of 200 RPM to
1000 RPM. The work piece is about .625 Dia. X 2.5 in long. Every time
I try to machine the OD I get a lot of chatter. Any ideas?

I'm not sure if I'm following your grind on the tool. Part of the problem
is that your bar is sticking out over 4x its length, so deflection will be
an issue. Once you have anything over 3-4x the diameter hanging out of the
chuck, you need to think about supporting the work, usually with the tail
stock. The other thing you need to do is keep the cutting forces low. This
means lower speeds and feeds, lighter depth of cuts, and a free cutting
tool geometry.

For the tool grind a positive lead creates more pressure, as does a full
radius. A positive side rake and back rake will help lower forces. I would
use a tool with zero lead, 5 degrees of end and side relief clearance, 12
degrees of side rake, and 10 degrees of back rake. Grind the tip to 80
degrees by grinding the ten degrees from the front. Stone the cutting edges
and stone a small radius of around .005" on the corner minding that you
maintain the 5 degree angle all the way around. This tool will cut freely
in most steels at light DOC. Run around 900 rpm and feed at .0015"-.0025"
for best results. Make sure the tool is dead on center to slightly above.
No more than a thousandth or so. Try a .01"-.02" radial DOC to start.


--

Dan

Chatter Problem
 

On Sun, 11 Dec 2005 20:20:25 -0800, "Kelly Jones"
wrote:

Hi guys. I'm trying to maching a small item on a lathe. It's going to be a
depth gauge, folloeing the directions givien the the Machinist's Bedside
Reader. The material is some sort of mild steel, pedigree unkonown. I have
ground a full radius tool from a peice of HSS. I have ground a 45 degree
cone on the end of the tool and a 10 degree rake (?) angle on the top
surface. I have tried speeds of 200 RPM to 1000 RPM.
The work piece is about .625 Dia. X 2.5 in long. Every time I try to
machine the OD I get a lot of chatter. Any ideas?
Thanks

Reduce the radius. Big radius is prone to chatter, lots of tool in
the cut. I very seldom use any radius, if the tool is sharp and the
feed right, finish will be good. As an alternative, you might try
taking lighter cuts, my guess is it won't help much.

Rich

Chatter Problem
 

....
I'm not sure if I'm following your grind on the tool. Part of the problem
is that your bar is sticking out over 4x its length, so deflection will be
an issue. Once you have anything over 3-4x the diameter hanging out of the
chuck, you need to think about supporting the work, usually with the tail
stock. The other thing you need to do is keep the cutting forces low. This
....

You gotta fix this to have a chance. Chuck in closer for this cut? Time to
build/buy a follow rest?

Karl

Chatter Problem
 

Kelly Jones wrote:

The work piece is about .625 Dia. X 2.5 in long. Every time I try to
machine the OD I get a lot of chatter. Any ideas?


Are you using a live center in the tailstock?


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

Chatter Problem
 

The tool bit grinding is pretty critical. You also need to check the
crossfeed and spindle for backlash. Didn't see any mention of the make
and size of lathe.
A 10" or 12" lathe wouldn't even tremble, but one of the small toys
would be prone to chatter, in my experience.
Bugs

Chatter Problem
 

""Nick Müller"" wrote in message
...
Kelly Jones wrote:

The work piece is about .625 Dia. X 2.5 in long. Every time I try to
machine the OD I get a lot of chatter. Any ideas?


Are you using a live center in the tailstock?


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

Not yet, good thought though. I'll give that a try.

Chatter Problem
 

"D Murphy" wrote in message
...
"Kelly Jones" wrote in
:

Hi guys. I'm trying to maching a small item on a lathe. It's going to
be a depth gauge, folloeing the directions givien the the Machinist's
Bedside Reader. The material is some sort of mild steel, pedigree
unkonown. I have ground a full radius tool from a peice of HSS. I
have ground a 45 degree cone on the end of the tool and a 10 degree
rake (?) angle on the top surface. I have tried speeds of 200 RPM to
1000 RPM. The work piece is about .625 Dia. X 2.5 in long. Every time
I try to machine the OD I get a lot of chatter. Any ideas?

I'm not sure if I'm following your grind on the tool. Part of the problem
is that your bar is sticking out over 4x its length, so deflection will be
an issue. Once you have anything over 3-4x the diameter hanging out of the
chuck, you need to think about supporting the work, usually with the tail
stock. The other thing you need to do is keep the cutting forces low. This
means lower speeds and feeds, lighter depth of cuts, and a free cutting
tool geometry.

For the tool grind a positive lead creates more pressure, as does a full
radius. A positive side rake and back rake will help lower forces. I would
use a tool with zero lead, 5 degrees of end and side relief clearance, 12
degrees of side rake, and 10 degrees of back rake. Grind the tip to 80
degrees by grinding the ten degrees from the front. Stone the cutting
edges
and stone a small radius of around .005" on the corner minding that you
maintain the 5 degree angle all the way around. This tool will cut freely
in most steels at light DOC. Run around 900 rpm and feed at .0015"-.0025"
for best results. Make sure the tool is dead on center to slightly above.
No more than a thousandth or so. Try a .01"-.02" radial DOC to start.



Ok. I think I follow: I currently have a full radius on the tool and a 45
degree "side relief" all the way around. The angle of the top of the tool
top the plane of the ways is about 5 to 10 degrees. This doesn't sound like
what you describe. Sounds like you are suggesting grinding two tools, one
for a left hand fillet and one for a right hand fillet, instead of trying to
make one tool cut both sides. I can do that. Hadn't thought about breaking
the edges of the tool though. I was thinking that the sharper the better.
I can radius the tool edges too. What's "DOC"? I was putting the tool dead
center to slightly low. I can fix that too.

The lathe is a 12 X 36 import, only a year old. It shouldn't be to lathe's
fault, just my inexperience. Thanks for the help.

Chatter Problem
 

I can radius the tool edges too. What's "DOC"? I was putting the tool
dead center to slightly low. I can fix that too.


DOC = Depth Of Cut

Chatter Problem
 

Clamp a vise-grip onto the tool shank. If it's vibrating the
extra weight will either stop it or reduce the chatter frequency. You
might have to make a stockier toolholder.

Dan