I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

I find that I can get excellent threads (comparatively) by setting up the
compound parallel to the longitudinal travel. You have to calculate the
depth of thread to go in (I think it's pitch * .6495, in radius, double the
value if your machine is in diameter).

Once you have threaded to this depth (the thread will look incorrect),
retract the compound about .001" and take a pass. Then advance the compound
roughly .002" past your original zero and take another pass. Use thread
measuring wires for the best fit, but you can just muck about with a nut if
you want.

This technique works so well because it independently cuts the leading and
trailing flanks.

I have found the surface grinding the top face of the cutter makes for an
excellent finish. I would assume grinding the side faces couldn't hurt
either.

Regards,

Robin


"Jim Stewart" wrote in message
...
I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Are you using cutting oil?
Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

In article ,
Jim Stewart wrote:
I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Charles A. Sherwood wrote:

Are you using cutting oil

Yes, tried lard oil and pipe cutting oil

Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

30 degrees until the end then last fine cut
straight in.

Light cuts. I don't have much choice at 28 tpi


In article ,
Jim Stewart wrote:

I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Robin S. wrote:

I find that I can get excellent threads (comparatively) by setting up the
compound parallel to the longitudinal travel. You have to calculate the
depth of thread to go in (I think it's pitch * .6495, in radius, double the
value if your machine is in diameter).

Once you have threaded to this depth (the thread will look incorrect),
retract the compound about .001" and take a pass. Then advance the compound
roughly .002" past your original zero and take another pass. Use thread
measuring wires for the best fit, but you can just muck about with a nut if
you want.

This technique works so well because it independently cuts the leading and
trailing flanks.

I have found the surface grinding the top face of the cutter makes for an
excellent finish. I would assume grinding the side faces couldn't hurt
either.

I'll give it a try tonight. Thanks.

Are you sure the helix angle (below the cutting edge) is allowing sufficient
clearance to prevent the tool from rubbing on the bore?

Bob Swinney
"Jim Stewart" wrote in message
...
Charles A. Sherwood wrote:

Are you using cutting oil

Yes, tried lard oil and pipe cutting oil

Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

30 degrees until the end then last fine cut
straight in.

Light cuts. I don't have much choice at 28 tpi


In article ,
Jim Stewart wrote:

I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Jim Stewart wrote in message ...
I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Try using a bit more rake, slightly less clearance than you normally
would. Possibly changing speeds, going just a bit higher, and using
regular old thread cutting oil. W-1 seems to like high sulfur oils.
LIghter cuts for the last little bit seems to help too. MIght want to
check that the back side of the tool isn't dragging, 5/8"-28 isn't a
whole lot of helix angle.

Bob Swinney wrote:

Are you sure the helix angle (below the cutting edge) is allowing sufficient
clearance to prevent the tool from rubbing on the bore?

No, that hadn't occured to me. I'll check it.


Bob Swinney
"Jim Stewart" wrote in message
...

Charles A. Sherwood wrote:


Are you using cutting oil

Yes, tried lard oil and pipe cutting oil


Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

30 degrees until the end then last fine cut
straight in.

Light cuts. I don't have much choice at 28 tpi



In article ,
Jim Stewart wrote:


I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

I assume that you are running pretty slow, 100 rpm or so,
like we're told is the way to cut threads. I sometimes
wonder if the combination of slow speeds and light feeds
just doesn't prevent the cutting edge from being able to
shear the material cleanly. I've noticed that the best
clean-up pass is .005 or so and at 300+ rpm. But obviously,
it isn't really possible to make a full speed threading cut
up to a face, so maybe you could use a right hand cutting
tool and cut off the end of the part???

Bob Swinney wrote:

Are you sure the helix angle (below the cutting edge) is allowing sufficient
clearance to prevent the tool from rubbing on the bore?

Bob Swinney
"Jim Stewart" wrote in message
...
Charles A. Sherwood wrote:

Are you using cutting oil

Yes, tried lard oil and pipe cutting oil

Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

30 degrees until the end then last fine cut
straight in.

Light cuts. I don't have much choice at 28 tpi


In article ,
Jim Stewart wrote:

I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

you need a really sharp tool with a very good positive top rake, take lots
of passes with a small depth of cut .oo2 per side max.

Jim Stewart

CAS
Are you advancing the compound at 30 degrees or straight in?
Heavy cuts or light cuts?

Jim
30 degrees until the end then last fine cut
straight in.

You advance the compound for all cuts. Why vary that for the last cut?
The last cut should be a "free ride," that is, advance nothing and run the
operation again. It will cut more metal.

The tip of the threads may crumble some. (I have no experience with W1).

Can you check with a nut to see if even a crumbled thread vee is acceptable?

Stone the threads after the final pass to clean up?

When you start, you check your tool with a center gauge to make sure it's dead
on? And know it's dead on center height?

Do you turn the right end of the work down to the minor diameter, so it tells
you when your toolbit tip hits there? Perhaps you are cutting too deep?

Frank Morrison

So far I haven't seen how you are supporting the rod. Are you using a dead
center or such? It sounds like lack of rigidity.

--
There are 10 kinds of people...Those that understand binary and those that
don't
"Jim Stewart" wrote in message
...
I've been trying to cut 28 tpi threads in a length of
W1 5/8" drill rod stock. So far, they come out
ragged to the point of uselessness. I'm a bit
frustrated because the steel turns beautifully.

I'm using hand-ground and diamond-honed HSS+10%
cobalt tools. I've had good luck cutting threads
in brass, bronze and AL. I've also made passable
large form threads in steel.

Anyone have any pointers?

Tom Gardner wrote:

So far I haven't seen how you are supporting the rod. Are you using a dead
center or such? It sounds like lack of rigidity.

4C collet with about an inch of stock sticking out.

Nevermind...

--
There are only 10 kinds of people...Those that understand binary and
those that don't.


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

So far I haven't seen how you are supporting the rod. Are you using a
dead
center or such? It sounds like lack of rigidity.

4C collet with about an inch of stock sticking out.

nic wrote:

clean-up pass is .005 or so and at 300+ rpm. But obviously,
it isn't really possible to make a full speed threading cut
up to a face,

If your lathe does _not_ have a screw on chuck, you can put the tool on
the back side of the work and run in reverse. That way, you cut away
from the shoulder and can cut at any speed you desire.

Ted