Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Interrupted Turning

What is the "old knowledge" about interrupted turning. I've been doing some
Google searches, and checking the videos on YouTube, but most results seem
to indicate a need for new high tech special inserts. Or more accurately be
aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if I
have to push it a little bit, but I'd kinda like to know how to do it the
"most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy away
from maxing out the motor if possible. Feed per rev is pretty flexible, and
its got spindle speeds from 70 upto 1255. Its more rigid than the average
Chicom lathe, but its still a Chicom lathe so I'd also like to shy away from
pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to this
with no qualms.

How you would you do it if you were going to hand grind an HSS insert for
the job?




P.S. For why guys no tell me about vertical shears. That's an sweome grind
for getting a smooth/er finish.



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"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been doing
some Google searches, and checking the videos on YouTube, but most results
seem to indicate a need for new high tech special inserts. Or more
accurately be aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if I
have to push it a little bit, but I'd kinda like to know how to do it the
"most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy away
from maxing out the motor if possible. Feed per rev is pretty flexible,
and its got spindle speeds from 70 upto 1255. Its more rigid than the
average Chicom lathe, but its still a Chicom lathe so I'd also like to shy
away from pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to this
with no qualms.

How you would you do it if you were going to hand grind an HSS insert for
the job?




P.S. For why guys no tell me about vertical shears. That's an sweome
grind for getting a smooth/er finish.


That should say "lathe bit," not "insert" in that question.



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Default Interrupted Turning

On Monday, October 31, 2016 at 8:24:00 PM UTC-4, Bob La Londe wrote:
What is the "old knowledge" about interrupted turning. I've been doing some
Google searches, and checking the videos on YouTube, but most results seem
to indicate a need for new high tech special inserts. Or more accurately be
aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if I
have to push it a little bit, but I'd kinda like to know how to do it the
"most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy away
from maxing out the motor if possible. Feed per rev is pretty flexible, and
its got spindle speeds from 70 upto 1255. Its more rigid than the average
Chicom lathe, but its still a Chicom lathe so I'd also like to shy away from
pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to this
with no qualms.

How you would you do it if you were going to hand grind an HSS insert for
the job?




P.S. For why guys no tell me about vertical shears. That's an sweome grind
for getting a smooth/er finish.


I don't have an answer for you, but it would probably help if you added some details about the material to be cut and its size and shape as far as it affects the "interruptedness" of the cut.
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Default Interrupted Turning

"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been
doing some Google searches, and checking the videos on YouTube, but
most results seem to indicate a need for new high tech special
inserts. Or more accurately be aimed at selling such inserts and
insert tools.

I don't have to do it often, so I don't mind if it takes a while or
if I have to push it a little bit, but I'd kinda like to know how to
do it the "most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a
3HP motor. So far this lathe does a pretty good job, but I'd like
to shy away from maxing out the motor if possible. Feed per rev is
pretty flexible, and its got spindle speeds from 70 upto 1255. Its
more rigid than the average Chicom lathe, but its still a Chicom
lathe so I'd also like to shy away from pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to
this with no qualms.

How you would you do it if you were going to hand grind an HSS
insert for the job?

P.S. For why guys no tell me about vertical shears. That's an
sweome grind for getting a smooth/er finish.


The first HSS bit I grab for quick jobs in aluminum, brass, mild and
harder steel and stainless is ground like a threading tool, but closer
to 90 degrees than 60 so the point holds up longer. The cutting edge
slants downhill toward the point as a result of freehand grinding, not
intent, but it's handy to remove the nub left on the stock from a
cutoff bit and not too sensitive to being a little off center height,
and quick to resharpen. It stood up to turning stainless squares into
circles for the races of a solar panel thrust bearing.

I don't think it's the ideal shape for any particular task but it
adapts well enough to a range of them. I originally ground it to turn
down straight pilot sections on stainless screws for my antenna. The
root-diameter pilots align inner and outer holes in telescoping mast
joints.

I should mention that I use Multifix tool holders that rotate in 9
degree steps, which is very convenient to compensate for the imprecise
angles of hand-ground bits. The Aloris system has a better selection
of insert toolholders.
http://www.lathes.co.uk/multifix/

--jsw


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Default Interrupted Turning

"Jim Wilkins" wrote in message
...
"Bob La Londe" wrote in message
...

The first HSS bit I grab for quick jobs in aluminum, brass, mild and
harder steel and stainless is ground like a threading tool, but
closer to 90 degrees than 60 so the point holds up longer. ...

--jsw


The angle is very close to the 80 degrees of a Trigon or Diamond
insert, which is good for both straight turning and facing a shoulder.
http://www.practicalmachinist.com/vb...tooling-91711/

--jsw




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Default Interrupted Turning

"rangerssuck" wrote in message
...
On Monday, October 31, 2016 at 8:24:00 PM UTC-4, Bob La Londe wrote:
What is the "old knowledge" about interrupted turning. I've been doing
some
Google searches, and checking the videos on YouTube, but most results
seem
to indicate a need for new high tech special inserts. Or more accurately
be
aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if I
have to push it a little bit, but I'd kinda like to know how to do it the
"most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy
away
from maxing out the motor if possible. Feed per rev is pretty flexible,
and
its got spindle speeds from 70 upto 1255. Its more rigid than the
average
Chicom lathe, but its still a Chicom lathe so I'd also like to shy away
from
pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to this
with no qualms.

How you would you do it if you were going to hand grind an HSS insert for
the job?




P.S. For why guys no tell me about vertical shears. That's an sweome
grind
for getting a smooth/er finish.


I don't have an answer for you, but it would probably help if you added
some details about the material to be cut and its size and shape as far as
it affects the "interruptedness" of the cut.


Well, I have two things on the shelf that get used from time to time.
Several long pieces of left over steel solid jack shaft opener shafts with a
key way full length.

Several pieces of hex 360 brass rod used for various custom parts.


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Default Interrupted Turning

"Jim Wilkins" wrote in message
...
"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been doing
some Google searches, and checking the videos on YouTube, but most
results seem to indicate a need for new high tech special inserts. Or
more accurately be aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if I
have to push it a little bit, but I'd kinda like to know how to do it the
"most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy
away from maxing out the motor if possible. Feed per rev is pretty
flexible, and its got spindle speeds from 70 upto 1255. Its more rigid
than the average Chicom lathe, but its still a Chicom lathe so I'd also
like to shy away from pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to this
with no qualms.

How you would you do it if you were going to hand grind an HSS insert for
the job?

P.S. For why guys no tell me about vertical shears. That's an sweome
grind for getting a smooth/er finish.


The first HSS bit I grab for quick jobs in aluminum, brass, mild and
harder steel and stainless is ground like a threading tool, but closer to
90 degrees than 60 so the point holds up longer. The cutting edge slants
downhill toward the point as a result of freehand grinding, not intent,
but it's handy to remove the nub left on the stock from a cutoff bit and
not too sensitive to being a little off center height, and quick to
resharpen. It stood up to turning stainless squares into circles for the
races of a solar panel thrust bearing.


So ultimately its the equialent of one point of a triagon with negative
rake?


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Posts: 5,888
Default Interrupted Turning


"Bob La Londe" wrote in message
...
"Jim Wilkins" wrote in message
...
"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been
doing some Google searches, and checking the videos on YouTube,
but most results seem to indicate a need for new high tech special
inserts. Or more accurately be aimed at selling such inserts and
insert tools.

I don't have to do it often, so I don't mind if it takes a while
or if I have to push it a little bit, but I'd kinda like to know
how to do it the "most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims
a 3HP motor. So far this lathe does a pretty good job, but I'd
like to shy away from maxing out the motor if possible. Feed per
rev is pretty flexible, and its got spindle speeds from 70 upto
1255. Its more rigid than the average Chicom lathe, but its still
a Chicom lathe so I'd also like to shy away from pounding on it to
hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one
to this with no qualms.

How you would you do it if you were going to hand grind an HSS
insert for the job?

P.S. For why guys no tell me about vertical shears. That's an
sweome grind for getting a smooth/er finish.


The first HSS bit I grab for quick jobs in aluminum, brass, mild
and harder steel and stainless is ground like a threading tool, but
closer to 90 degrees than 60 so the point holds up longer. The
cutting edge slants downhill toward the point as a result of
freehand grinding, not intent, but it's handy to remove the nub
left on the stock from a cutoff bit and not too sensitive to being
a little off center height, and quick to resharpen. It stood up to
turning stainless squares into circles for the races of a solar
panel thrust bearing.


So ultimately its the equialent of one point of a triagon with
negative rake?


It has some positive top rake sideways away from the cutting edge, not
enough that I recall having a problem with it on brass. The goal was
an easy-to-resharpen shape for roughing cuts on unidentified scrap
metal but it also seems to have less impact on interrupted cuts like
the stainless squares.



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Default Interrupted Turning

"Jim Wilkins" wrote in message
...

"Bob La Londe" wrote in message
...
"Jim Wilkins" wrote in message
...
"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been doing
some Google searches, and checking the videos on YouTube, but most
results seem to indicate a need for new high tech special inserts. Or
more accurately be aimed at selling such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while or if
I have to push it a little bit, but I'd kinda like to know how to do it
the "most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a 3HP
motor. So far this lathe does a pretty good job, but I'd like to shy
away from maxing out the motor if possible. Feed per rev is pretty
flexible, and its got spindle speeds from 70 upto 1255. Its more
rigid than the average Chicom lathe, but its still a Chicom lathe so
I'd also like to shy away from pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to
this with no qualms.

How you would you do it if you were going to hand grind an HSS insert
for the job?

P.S. For why guys no tell me about vertical shears. That's an sweome
grind for getting a smooth/er finish.

The first HSS bit I grab for quick jobs in aluminum, brass, mild and
harder steel and stainless is ground like a threading tool, but closer
to 90 degrees than 60 so the point holds up longer. The cutting edge
slants downhill toward the point as a result of freehand grinding, not
intent, but it's handy to remove the nub left on the stock from a cutoff
bit and not too sensitive to being a little off center height, and quick
to resharpen. It stood up to turning stainless squares into circles for
the races of a solar panel thrust bearing.


So ultimately its the equialent of one point of a triagon with negative
rake?


It has some positive top rake sideways away from the cutting edge, not
enough that I recall having a problem with it on brass. The goal was an
easy-to-resharpen shape for roughing cuts on unidentified scrap metal but
it also seems to have less impact on interrupted cuts like the stainless
squares.


Well, I just did it, and it was not bad. I went with a very conservative
right hand turning tool. About 5 degrees back angle on the leading cutting
edge and somewhere just a little less than 90 degrees, but not much,
included angle. Slight under cut on leading face and front face. 7 Degrees
maybe. About the same as the bit already came. Just rotated to match the
right hand included angle. I didn't get to fancy with the corner radius.
Somewhere between 1/32 and 1/16 radius. I gave it a very slight back rake
on top away from the cutting edge. When it looked ok I just stopped, and
honed the edges.

I can definitely see why "real machinists" like a bigger grinder. On my
little 6" with its half wore out wheels the faces of the bit have a very
noticeable scallop. (Yes I squared it first.)

Then on some mild steel jack shaft with a keyway cut full length (more
likely extruded that way) I gave it a try. I ran about .05 depth of cut,
then .1 depth of cut, then .145 depth of cut. At .05 it cut almost like
cutting regular shaft. At .1 it made some noise, but if I didn't know what
it was I might have only noticed a difference in pitch. At .14 (completely
removing the keyway in one pass) it made some noise and it was pulling the
lathe bit into the work piece. Overall I was really impressed, although I
suspect it was as much the heavier lathe I was using as the cutter. Still
it did the job, and the lathe bit still looks good. The feed was pretty
small. .0014 I think. I also played with RPM at 115, 190, and 300. They
all seemed to cut the same, but I didn't get straw turning to blue colored
chips on the lighter DOCs until I bumped it to 300. I suspect I could crank
the RPM up some more at the lightest DOC of .05.

The lathe bit looks virtually just like it did after I honed it. I'll look
at it with the loupe in a few minutes, but it looks good. It will certainly
last more than long enough for basic common interrupted type cuts. Best
part is I can regrind this in just a couple minutes anytime I need to.

That's good for me. 300 RPM and .014 feed is where I leave the lathe most
of the time.

Now for my next cut hand grind. A vertical shear so I can cut better
finishes before I polish on those generic mild steels.


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Default Interrupted Turning


P.S. I might add before I tackled the interrupted cut I tested the lathe
bit on a 1" piece of 304 stainless. It was really really good. I think
I've been selling myself short by not hand grinding more HSS bits.




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Default Interrupted Turning

"Bob La Londe" wrote in message
...
"Jim Wilkins" wrote in message
...

"Bob La Londe" wrote in message
...
"Jim Wilkins" wrote in message
...
"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've
been doing some Google searches, and checking the videos on
YouTube, but most results seem to indicate a need for new high
tech special inserts. Or more accurately be aimed at selling
such inserts and insert tools.

I don't have to do it often, so I don't mind if it takes a while
or if I have to push it a little bit, but I'd kinda like to know
how to do it the "most effectively" with teh tools I have.

I've got a Precision Mathews PM1440-LB 14 x 40 lathe that
claims a 3HP motor. So far this lathe does a pretty good job,
but I'd like to shy away from maxing out the motor if possible.
Feed per rev is pretty flexible, and its got spindle speeds from
70 upto 1255. Its more rigid than the average Chicom lathe, but
its still a Chicom lathe so I'd also like to shy away from
pounding on it to hard.

I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one
to this with no qualms.

How you would you do it if you were going to hand grind an HSS
insert for the job?

P.S. For why guys no tell me about vertical shears. That's an
sweome grind for getting a smooth/er finish.

The first HSS bit I grab for quick jobs in aluminum, brass, mild
and harder steel and stainless is ground like a threading tool,
but closer to 90 degrees than 60 so the point holds up longer.
The cutting edge slants downhill toward the point as a result of
freehand grinding, not intent, but it's handy to remove the nub
left on the stock from a cutoff bit and not too sensitive to
being a little off center height, and quick to resharpen. It
stood up to turning stainless squares into circles for the races
of a solar panel thrust bearing.


So ultimately its the equialent of one point of a triagon with
negative rake?


It has some positive top rake sideways away from the cutting edge,
not enough that I recall having a problem with it on brass. The
goal was an easy-to-resharpen shape for roughing cuts on
unidentified scrap metal but it also seems to have less impact on
interrupted cuts like the stainless squares.


Well, I just did it, and it was not bad. I went with a very
conservative right hand turning tool. About 5 degrees back angle on
the leading cutting edge and somewhere just a little less than 90
degrees, but not much, included angle. Slight under cut on leading
face and front face. 7 Degrees maybe. About the same as the bit
already came. Just rotated to match the right hand included angle.
I didn't get to fancy with the corner radius. Somewhere between 1/32
and 1/16 radius. I gave it a very slight back rake on top away from
the cutting edge. When it looked ok I just stopped, and honed the
edges.

I can definitely see why "real machinists" like a bigger grinder.
On my little 6" with its half wore out wheels the faces of the bit
have a very noticeable scallop. (Yes I squared it first.)

Then on some mild steel jack shaft with a keyway cut full length
(more likely extruded that way) I gave it a try. I ran about .05
depth of cut, then .1 depth of cut, then .145 depth of cut. At .05
it cut almost like cutting regular shaft. At .1 it made some noise,
but if I didn't know what it was I might have only noticed a
difference in pitch. At .14 (completely removing the keyway in one
pass) it made some noise and it was pulling the lathe bit into the
work piece. Overall I was really impressed, although I suspect it
was as much the heavier lathe I was using as the cutter. Still it
did the job, and the lathe bit still looks good. The feed was
pretty small. .0014 I think. I also played with RPM at 115, 190,
and 300. They all seemed to cut the same, but I didn't get straw
turning to blue colored chips on the lighter DOCs until I bumped it
to 300. I suspect I could crank the RPM up some more at the
lightest DOC of .05.

The lathe bit looks virtually just like it did after I honed it.
I'll look at it with the loupe in a few minutes, but it looks good.
It will certainly last more than long enough for basic common
interrupted type cuts. Best part is I can regrind this in just a
couple minutes anytime I need to.

That's good for me. 300 RPM and .014 feed is where I leave the
lathe most of the time.

Now for my next cut hand grind. A vertical shear so I can cut
better finishes before I polish on those generic mild steels.


Glad to help.

I grind blank bits nearly to shape with an angle grinder before
finishing on the pedestal grinder, or the surface grinder for
threading bits and gear cutters.

You can grind a concave corner rounding bit with a conical stone held
vertically relative to the final position on the lathe.

--jsw


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Default Interrupted Turning

"Bob La Londe" wrote in message
...

P.S. I might add before I tackled the interrupted cut I tested the
lathe bit on a 1" piece of 304 stainless. It was really really
good. I think I've been selling myself short by not hand grinding
more HSS bits.


I've noticed that what really matters is keeping the wear flat below
the cutting edge less than about 1/32" high, in agreement with the
experimental edge geometry results in the Cincinnati Milling Machine
book from Lindsay. Top rake angle (or none) and having the bit below
center don't make too much difference. I no longer bother to measure
angles.
--jsw


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