Joseph Gwinn wrote:
In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:


" fired this volley in news:7080e05e-
:

Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.

That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)


I assume you are going to use a steady rest...............

Would, but mine won't open to 6.5".


It's fairly easy to cob one up from aluminum plate for a known diameter.



You might also see if you can get some aluminum hollow bar.

??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)


For honing I would look at flexible hones.


Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.

I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.

Given that the bore is quite large, the bar can be quite stout. It
would help if it were hollow except in the center where the bit is
mounted. The intent is to raise the resonant frequency of the boring
bar, for which one increases rigidity and reduces mass. Support from
both ends also helps.

Joe Gwinn

Paul Drahn fired this volley in news:jc34g4$gn$1
@dont-email.me:

Is your customer concerned about the outside of the tube, as far as
being a constant OD? I think the ball or torpedo pulled or pushed
through the tube might stretch it enough to get the job done.


nope.. no issues with the o.d. The only problem I see with that is that
the device would have to take the aluminum past its elastic limit, or it
would spring back to out-of-round, unless already trued up.

Lloyd

On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:

Joseph Gwinn wrote:
In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:


" fired this volley in news:7080e05e-
:

Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.

That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)


I assume you are going to use a steady rest...............

Would, but mine won't open to 6.5".


It's fairly easy to cob one up from aluminum plate for a known diameter.



You might also see if you can get some aluminum hollow bar.

??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)


For honing I would look at flexible hones.


Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.

I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.

T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.

--
Ed Huntress


Given that the bore is quite large, the bar can be quite stout. It
would help if it were hollow except in the center where the bit is
mounted. The intent is to raise the resonant frequency of the boring
bar, for which one increases rigidity and reduces mass. Support from
both ends also helps.

Joe Gwinn

On Sun, 11 Dec 2011 15:14:00 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Paul Drahn fired this volley in news:jc34g4$gn$1
:

Is your customer concerned about the outside of the tube, as far as
being a constant OD? I think the ball or torpedo pulled or pushed
through the tube might stretch it enough to get the job done.


nope.. no issues with the o.d. The only problem I see with that is that
the device would have to take the aluminum past its elastic limit, or it
would spring back to out-of-round, unless already trued up.

Lloyd

If straightness is an issue, ball-sizing or hard-honing are not going
to do it. They're good for roundness, and ball-sizing is good for
diametral accuracy. A huge bar holding a hard Sunnen hone would give
you the straightness, but now you're talking some pricey tooling. The
hard hones, unlike the flexible ones, make their own path. They don't
tend to follow the existing bore.

Boring has an advantage in achieving straightness and roundness, as
long as the boring bar's flex is minimal.

--
Ed Huntress

On Dec 11, 4:34*pm, Ed Huntress wrote:


T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.

--
Ed Huntress


http://www.statecollegecentral.com/metallathe/

Dan

On 12/10/2011 11:15 AM, Lloyd E. Sponenburgh wrote:
I must bore and hone a 6061 6.125" cylinder 15" long on my 14x40 lathe.

It must be smooth and round, but the actual i.d. is not important (except
to document on the drawings).

I have no experience boring long, large tubes, and figure tool flex is
going to be the primary problem.

Any hints on what size boring bar and cuts I'm going to have to take to
make this work? (none of the local machine shops, including a marine
diesel shop, will take it on).

LLoyd
I don't pretend to know about the other posters, but you have reached
the limit of my imagination and help.

Let us know the results.

Paul

Ed Huntress wrote:
On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:


Joseph Gwinn wrote:

In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:



" fired this volley in news:7080e05e-
:


Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.


That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)



I assume you are going to use a steady rest...............


Would, but mine won't open to 6.5".


It's fairly easy to cob one up from aluminum plate for a known diameter.




You might also see if you can get some aluminum hollow bar.


??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)



For honing I would look at flexible hones.


Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.


I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.


T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.


I didn't realise they were a British thing but my Kerry 1140
http://www.lathes.co.uk/kerry/page2.html has 2 slots as standard. A mate
has a WWII era Southbend so the next time I'm over there I have a look
and see if it has a T slot cross slide . IIRC his father has shown him
how to do milling on the lathe so it's possible it has the T slots.

Dan in the other response posted a source of the T slot Southbend cross
slide castings, do you still have the inclination to make one and if so
do you have the time?

On Sun, 11 Dec 2011 23:21:37 +0000, David Billington
wrote:

Ed Huntress wrote:
On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:


Joseph Gwinn wrote:

In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:



" fired this volley in news:7080e05e-
:


Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.


That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)



I assume you are going to use a steady rest...............


Would, but mine won't open to 6.5".


It's fairly easy to cob one up from aluminum plate for a known diameter.




You might also see if you can get some aluminum hollow bar.


??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)



For honing I would look at flexible hones.


Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.


I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.


T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.


I didn't realise they were a British thing but my Kerry 1140
http://www.lathes.co.uk/kerry/page2.html has 2 slots as standard.

That looks like a very nice lathe.

A mate
has a WWII era Southbend so the next time I'm over there I have a look
and see if it has a T slot cross slide . IIRC his father has shown him
how to do milling on the lathe so it's possible it has the T slots.

Yeah. I don't know if they made all of them that way, but I know that
was the source of some of them that wound up in the US in the early
'50s. I've seen a couple of old ones here.


Dan in the other response posted a source of the T slot Southbend cross
slide castings, do you still have the inclination to make one and if so
do you have the time?

Aha. Well, the issue now for me is getting the milling done, and the
total cost. I scrapped my milling machine this past summer (a 1917
Taylor & Fenn knee mill that was in need of scraping and lead screws,
or a new mill), and I haven't replaced it yet.

It's not something I'd use all the time but I used to make model steam
engines and it's really nice for line-boring and for some milling
jobs. If I get time, I'd like to make some IC engines. It might be
worth it if it looks like I'll have that much time to get back to
hobby machining. Right now, I don't.

--
Ed Huntress

"David Billington" wrote in message
...
... Dan in the other response posted a source of the T slot Southbend
cross slide castings, do you still have the inclination to make one and if
so do you have the time?

My first night-school milling project was a cross slide for a 6" Craftsman
lathe, the base of of a homebrew milling attachment. It was simply a steel
plate with a lengthwise dovetail slot, cut to a loose fit on the saddle
dovetail plus the gib stock. I drilled the top to take the original lead
screw nut and added more tapped holes as needed to attach the milling vise
vertical slide and brace. Tee slots on top would have weakened it
excessively. A plate thick enough for them would have cut into my working
clearance below the spindle.

If you can't borrow and adapt the leadscrew nut you could probably snug the
gib screws and nudge the work centered with a C clamp. The old South Bend
saddle had the slots out in the corners near the felt way wipers and the
work had to be supported on crosswise bars and shimmed and tapped into
alignment.
http://www.lathes.co.uk/southbend/page2.html

jsw

If you use a boring bar or pipe or whatever - Try the idea I did.

I had a long carbide bar for a long cut in gray iron.
What I did was realize that the back side had plenty of inside room
for 'beefing up'. I had a right angle bar that was really scrap from
a milling task. It was, by it's shape, rigid itself. I laid the angle
across the back of the bar and super glued it on. It stayed on nicely.
Oil finally got it off. But the job was done and sat in the tool box
that way for some months. Maybe it was the temperature change that
released the bond. I suspect that now. Coefficient of linear expansion
is different on carbide and Stainless Steel (the heavy right angle.

Martin

On 12/11/2011 9:36 AM, Baron wrote:
"Lloyd E. Sponenburgh"lloydspinsidemindspring.com Inscribed thus:

Jon fired this volley in
:

ou may be able to bore in from each side with a large Morse taper
drill
to get things started. Of course, you can also buy aluminum tubes
to get close to final size off the shelf.

Jon


Wha??? Hmmm... I said "bore", but didn't say "drill and bore".

I guess I wasn't clear on this, because someone else recommended
"hollow rod".

This is a piece of 6" i.d. (nom) aluminum pipe with 1/4" walls. It's
approximately .050" out of round, and is extruded, so not smooth.

I must bore it round, and hone it smooth. Not even the biggest marine
engine shop within 60 miles of me will take it on, because "it's not
in a
block" (basically). They won't lathe bore it. They won't line bore
it.
they won't "boring machine" bore it.sigh

LLoyd

I wonder if using a steel ball, pressed through the bore would do what
you want. I've seen 100mm bores trued in a similar fashion.

On Dec 10, 2:23*pm, Ed Huntress wrote:
On Sat, 10 Dec 2011 15:42:26 -0600, "Lloyd E. Sponenburgh"









lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4ee3ce18$0$29494
:

On 6061 AL I'd think so, it cuts pretty easily so you shouldn't have too
much cutting load trying to flex the bar.

That's my hope.

I have a piece of 16" long 1"o.d. O-1 drill rod I will drill a cross-hole
into to accept a small insert bar.

If the cuts are small, the surface speed is adequate, and I don't get in a
hurry, I think I can do this.

LLoyd

Excuse me for being the naysayer, but I think you're talking about
inventing a new musical instument. g I'm not much with the
natural-frequency nomographs, but your vibration frequency appears to
be in the audible range.

Deflection is going to be unacceptably high, IMO. A 20-pound force at
the cutter will deflect the bar by 0.018".

OTOH, a 3-inch-diameter piece of steel water pipe with 1/8-inch-thick
walls (much liked by us cheapskates) would deflect only 0.0007".

Here are some calculators that can help:

http://www.calculatoredge.com/civil%...beam.htm#round

--
Ed Huntress

I wonder if you made some sort of truss set up on the boring bar if
you could increase the rigidity of the boring bar to acceptable
limits? what I picture is your 3" pipe with a flange welded to each
end with some rods welded to one of the flanges and passing through
the flange on the other end, where you could pre-load the rods by
turning nuts.

Another idea would be to weld some "fins" along the axis of the pipe.

Roger Shoaf

On Sun, 11 Dec 2011 21:43:03 -0800 (PST), RS at work
wrote:

On Dec 10, 2:23*pm, Ed Huntress wrote:
On Sat, 10 Dec 2011 15:42:26 -0600, "Lloyd E. Sponenburgh"









lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4ee3ce18$0$29494
:

On 6061 AL I'd think so, it cuts pretty easily so you shouldn't have too
much cutting load trying to flex the bar.

That's my hope.

I have a piece of 16" long 1"o.d. O-1 drill rod I will drill a cross-hole
into to accept a small insert bar.

If the cuts are small, the surface speed is adequate, and I don't get in a
hurry, I think I can do this.

LLoyd

Excuse me for being the naysayer, but I think you're talking about
inventing a new musical instument. g I'm not much with the
natural-frequency nomographs, but your vibration frequency appears to
be in the audible range.

Deflection is going to be unacceptably high, IMO. A 20-pound force at
the cutter will deflect the bar by 0.018".

OTOH, a 3-inch-diameter piece of steel water pipe with 1/8-inch-thick
walls (much liked by us cheapskates) would deflect only 0.0007".

Here are some calculators that can help:

http://www.calculatoredge.com/civil%...beam.htm#round

--
Ed Huntress

I wonder if you made some sort of truss set up on the boring bar if
you could increase the rigidity of the boring bar to acceptable
limits? what I picture is your 3" pipe with a flange welded to each
end with some rods welded to one of the flanges and passing through
the flange on the other end, where you could pre-load the rods by
turning nuts.

Another idea would be to weld some "fins" along the axis of the pipe.

Roger Shoaf

I'm not good at the stiffness and strength values for various shapes,
but for a tube or round rod, the stiffness increases as to the cube of
the diameter. And a rod of a given diameter is only slightly stiffer
than a thick-walled tube of the same diameter.

The most efficient way to get greater stiffness, then, is to increase
the tube diameter. So a piece of water pipe of 3" or greater diameter
is likely the most cost-effective way to get adequate stiffness for
this job. You'd need at least a 3" diameter of steel for a 16" length,
and more is better.

--
Ed Huntress

"Ed Huntress" wrote in message
...

If straightness is an issue, ball-sizing or hard-honing are not going
to do it. They're good for roundness, and ball-sizing is good for
diametral accuracy. A huge bar holding a hard Sunnen hone would give
you the straightness, but now you're talking some pricey tooling. The
hard hones, unlike the flexible ones, make their own path. They don't
tend to follow the existing bore.

Boring has an advantage in achieving straightness and roundness, as
long as the boring bar's flex is minimal.

--
Ed Huntress

Maybe cobble up a twinbore something like this:

http://images.craigslist.org/5Q55U15...f0626d1c29.jpg

Could solve the deflection problem and help with chatter. The finish should
be adaquite for honing. When i have some tinkering time i want to make a
set.

Best Regards
Tom.

On Mon, 12 Dec 2011 02:00:10 -0800, "Howard Beal"
wrote:


"Ed Huntress" wrote in message
.. .

If straightness is an issue, ball-sizing or hard-honing are not going
to do it. They're good for roundness, and ball-sizing is good for
diametral accuracy. A huge bar holding a hard Sunnen hone would give
you the straightness, but now you're talking some pricey tooling. The
hard hones, unlike the flexible ones, make their own path. They don't
tend to follow the existing bore.

Boring has an advantage in achieving straightness and roundness, as
long as the boring bar's flex is minimal.

--
Ed Huntress

Maybe cobble up a twinbore something like this:

http://images.craigslist.org/5Q55U15...f0626d1c29.jpg

Could solve the deflection problem and help with chatter. The finish should
be adaquite for honing. When i have some tinkering time i want to make a
set.

Best Regards
Tom.

Maybe. Those things are a mixed blessing. They double the torsional
force on the boring bar but they slash the side load. From an
engineering point of view, I've always thought they were screwed up,
because they defeat the primary virtue of single-point boring:
cylindricity determined by the rotation of the spindle, which, if your
spindle bearings are decent, approaches a true circle.

But I reported on their actual use when I was covering tooling, and
the tool companies and users alike said they actually produce very
good bores, and they do it faster.

They have another virtue in deep boring on small lathes: they prevent
the lifting force on the tailstock end of the saddle, which can be
considerable with a very long boring bar. That lifting force can be a
significant contributor to chatter.

Anyway, it's an expensive piece of tooling justified, perhaps, in
commercial work, but you'd need to use it with some regularity to
justify the cost.

--
Ed Huntress

On Sat, 10 Dec 2011 13:15:25 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I must bore and hone a 6061 6.125" cylinder 15" long on my 14x40 lathe.

It must be smooth and round, but the actual i.d. is not important (except
to document on the drawings).

I have no experience boring long, large tubes, and figure tool flex is
going to be the primary problem.

Any hints on what size boring bar and cuts I'm going to have to take to
make this work? (none of the local machine shops, including a marine
diesel shop, will take it on).

LLoyd
Greetings Lloyd,
You have gotten many suggestions already. Making a bar from pipe will
help with the rigidity issue. Since you are only doing one and are
going to hone it I would suggest grinding the tool tip with a very
small radius. .005" would do. Run the lathe as slow as possible, use
cutting oil, and try dampening the vibrations with your fingers.
Sometimes when I do jobs like this I oil the outside of the tube and
press my fingers against the rotating workpiece to dampen vibrations.
It does wear out your fingers so holding a small piece of leather or
wearing a leather glove helps. I know this can be dangerous. I
probably wouldn't let someone do the above in my shop. But I do do it.
The finish will suck with the small radius tipped bar but you are
honing it anyway. If you are considering sending it out I can
recommend a very good shop in the Seattle area. They do a great job at
a reasonable price.
Eric

fired this volley in
:

It does wear out your fingers so holding a small piece of leather or
wearing a leather glove helps. I know this can be dangerous. I
probably wouldn't let someone do the above in my shop. But I do do it.


The problems with that are the following:

1) the "finger technique" works fine when you can grip the boring bar
fairly near the cutter. I do it all the time. It does not do much good
if you have to grip it 3/4-way back to the tool rest.

2) I'd have to reach about a foot into a spinning workpiece without being
able to clearly see my hand/fingers, and also would then have only one
hand left to run the machine (from an odd body position).

I don't think I'm quite ready for that. G

I have quite nearly given up on this workpiece. Although it will cost me
"an arm and a leg" (though not as quickly as the above method), I believe
I'm going to settle for the wait time to purchase a body tube for a large
pneumatic cylinder.

I made a really beefy (3" steel tube) boring bar, and found only that the
flex in my compound/cross slide is still too much to keep the bit from
singing excessively.

LLoyd

On 12/12/2011 12:46 PM, Lloyd E. Sponenburgh wrote:

I made a really beefy (3" steel tube) boring bar, and found only that the
flex in my compound/cross slide is still too much to keep the bit from
singing excessively.
Yup, that was my worry. Only an insanely HUGE lathe would be stiff
enough to handle a boring bar with 15" overhang. I have a 3500-Lb
Sheldon 15" lathe, and I really doubt it could handle such a nasty
job properly.

Jon

On 12/12/2011 01:36 PM, Ed Huntress wrote:
On Mon, 12 Dec 2011 12:46:02 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:



I made a really beefy (3" steel tube) boring bar, and found only that the
flex in my compound/cross slide is still too much to keep the bit from
singing excessively.

LLoyd


That's what I expected. For the thought exercise, you may want to
consider what you could try if you really *had* to get this job done:

You could, for example, make your tubular boring bar a lot longer, and
support the outboard end at the tailstock with a dead center.

Even better, would be to put the boring bit in the middle of a 30"+ bar,
and have a support at the back of the spindle end.
This would give support at both ends of the boring bar. Maybe you could
even rig up something with ball bearings and adjusting screws bolted to
the rear of the headstock so that it could keep the bar straight as you
advanced it for progressive cuts.

(Pretty soon we'll be giving detailed plans to convert your lathe to a
horizontal boring machine from the old "Bull of the woods" cartoons.)

Jon

On Dec 10, 12:15*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
I must bore and hone a 6061 6.125" cylinder 15" long on my 14x40 lathe.

It must be smooth and round, but the actual i.d. is not important (except
to document on the drawings).

I have no experience boring long, large tubes, and figure tool flex is
going to be the primary problem.

Any hints on what size boring bar and cuts I'm going to have to take to
make this work? *(none of the local machine shops, including a marine
diesel shop, will take it on).

LLoyd

I've done a couple of mortars on a SB lathe that was rather inadequate
for the job. I started with some offcuts from a large equipment
manufacturer, were pieces of chrome-moly tubular bar used for
hydraulic cylinders on the equipment. A steady rest WAS needed. I
had previously built a boring bar holder which could take a 1" bar and
I ended up making a long enough bar. It was tedious, but I got it
done, with several garbage bags of swarf, too. Since that long a bar
has a lot of spring to it, I ended up doing the bore in sections with
a light cut from end to end afterwards. Bore length was on the order
of 20" or so.

What you might consider is looking up a "packed bit" which was used
for making cannon bores. Usually used hardwood for a bearing surface
and the cutting part was packed up with slips of paper. Make one
pass, add a slip, until the finished size. archive.org or Gutenberg
has the copy of the ordnance manual I have in paper. That's the way
they did all the really big guns.

I guess the question is how much material do you really have to
remove? You said 1/4" walls on the blank, are we talking a few
thousandths or are you going for broke and going for foil-thin?

Stan

fired this volley in news:8323c3ee-df2a-4390-9107-
:


I guess the question is how much material do you really have to
remove? You said 1/4" walls on the blank, are we talking a few
thousandths or are you going for broke and going for foil-thin?

Stan, I only needed to remove about 25-thou, overall.

The problem is simply one of economy. I can build a tool to do this, and
if I needed to do it often, it would be reasonable. But I'm not going to
build an expensive tool for a 1-off -- not even a "packed bit" which is
the simplest mechanism.

However, were I to build such, it would have bearing followers, and an
adjustable cutter. Then I wouldn't need to use up all my printer paper
for shims! G

I found a piece of air cylinder stock long enough to make two of these
cylinders for what it would have cost me for 1/2 a lost day. So I only
ruined a 1/2 day experimenting.

LLoyd

Ed Huntress wrote:
On Sun, 11 Dec 2011 23:21:37 +0000, David Billington
wrote:


Ed Huntress wrote:

On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:



Joseph Gwinn wrote:


In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:




" fired this volley in news:7080e05e-
:



Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.



That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)




I assume you are going to use a steady rest...............



Would, but mine won't open to 6.5".



It's fairly easy to cob one up from aluminum plate for a known diameter.





You might also see if you can get some aluminum hollow bar.



??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)




For honing I would look at flexible hones.



Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.



I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.


T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.



I didn't realise they were a British thing but my Kerry 1140
http://www.lathes.co.uk/kerry/page2.html has 2 slots as standard.


That looks like a very nice lathe.

I imagine it was a very nice lathe when new but I bought it used and
learned a few things about buying a lathe. Overall I think I didn't do
badly and it has done some good work. It's worn in the ways and the
headstock gears are noisy in the slower speeds but I keep it as I have
the space and I use it for things I wouldn't want to do on the much
better condition Harrison M300. Looking at the Kerry it would seem to be
a bit more heavily constructed than the Harrison even though only an
11" lathe as compared to the 13" of the M300. Having used the Kerry for
a number of years and now the M300 I sometimes find it odd to reach past
the chuck to the clutch on the back of the headstock on the Kerry
thinking what would I do if something went wrong and needed to stop it
as the M300 has the safety neurosis off foot bar and brake below the
bed. I also have this idea of raising the headstock and tailstock on the
Kerry on blocks to increase the swing as most of what I do with it these
days is metal spinning. I may do that about the same time as you do the
cross slide.

A mate
has a WWII era Southbend so the next time I'm over there I have a look
and see if it has a T slot cross slide . IIRC his father has shown him
how to do milling on the lathe so it's possible it has the T slots.


Yeah. I don't know if they made all of them that way, but I know that
was the source of some of them that wound up in the US in the early
'50s. I've seen a couple of old ones here.

What happens when someone sees one of those and doesn't realise it
wasn't made by Southbend in the US. I would imagine that could be the
cause of some heated arguments.

Dan in the other response posted a source of the T slot Southbend cross
slide castings, do you still have the inclination to make one and if so
do you have the time?


Aha. Well, the issue now for me is getting the milling done, and the
total cost. I scrapped my milling machine this past summer (a 1917
Taylor & Fenn knee mill that was in need of scraping and lead screws,
or a new mill), and I haven't replaced it yet.

It's not something I'd use all the time but I used to make model steam
engines and it's really nice for line-boring and for some milling
jobs. If I get time, I'd like to make some IC engines. It might be
worth it if it looks like I'll have that much time to get back to
hobby machining. Right now, I don't.


That's what I was thinking, it would be a nice thing to have if you had
the time and tools to make it, but you seem busy. Hopefully you get the
time and the opportunity to make one and prove its usefulness.

On Mon, 12 Dec 2011 21:42:56 +0000, David Billington
wrote:

Ed Huntress wrote:
On Sun, 11 Dec 2011 23:21:37 +0000, David Billington
wrote:


Ed Huntress wrote:

On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:



Joseph Gwinn wrote:


In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:




" fired this volley in news:7080e05e-
:



Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.



That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)




I assume you are going to use a steady rest...............



Would, but mine won't open to 6.5".



It's fairly easy to cob one up from aluminum plate for a known diameter.





You might also see if you can get some aluminum hollow bar.



??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)




For honing I would look at flexible hones.



Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.



I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.


T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.



I didn't realise they were a British thing but my Kerry 1140
http://www.lathes.co.uk/kerry/page2.html has 2 slots as standard.


That looks like a very nice lathe.

I imagine it was a very nice lathe when new but I bought it used and
learned a few things about buying a lathe. Overall I think I didn't do
badly and it has done some good work. It's worn in the ways and the
headstock gears are noisy in the slower speeds but I keep it as I have
the space and I use it for things I wouldn't want to do on the much
better condition Harrison M300. Looking at the Kerry it would seem to be
a bit more heavily constructed than the Harrison even though only an
11" lathe as compared to the 13" of the M300. Having used the Kerry for
a number of years and now the M300 I sometimes find it odd to reach past
the chuck to the clutch on the back of the headstock on the Kerry
thinking what would I do if something went wrong and needed to stop it
as the M300 has the safety neurosis off foot bar and brake below the
bed. I also have this idea of raising the headstock and tailstock on the
Kerry on blocks to increase the swing as most of what I do with it these
days is metal spinning. I may do that about the same time as you do the
cross slide.

A mate
has a WWII era Southbend so the next time I'm over there I have a look
and see if it has a T slot cross slide . IIRC his father has shown him
how to do milling on the lathe so it's possible it has the T slots.


Yeah. I don't know if they made all of them that way, but I know that
was the source of some of them that wound up in the US in the early
'50s. I've seen a couple of old ones here.

What happens when someone sees one of those and doesn't realise it
wasn't made by Southbend in the US. I would imagine that could be the
cause of some heated arguments.

Oh, when they get that old, I don't think anyone gets excited about a
lathe's origins. The condition is everything.

BTW, I don't know if what I saw was actually British-made SBs, or just
the British-made cross-slides on a US-built lathe. As far as I know,
they were basically the same.

There also were some Bridgeport mills made by Beaver during the war. A
few of those are over here, too, if they haven't all been scrapped by
now. I don't know for sure if they were exact clones made under
license, but I think they were. In the years since, Beaver has
modified the old Bridgeport design.


Dan in the other response posted a source of the T slot Southbend cross
slide castings, do you still have the inclination to make one and if so
do you have the time?


Aha. Well, the issue now for me is getting the milling done, and the
total cost. I scrapped my milling machine this past summer (a 1917
Taylor & Fenn knee mill that was in need of scraping and lead screws,
or a new mill), and I haven't replaced it yet.

It's not something I'd use all the time but I used to make model steam
engines and it's really nice for line-boring and for some milling
jobs. If I get time, I'd like to make some IC engines. It might be
worth it if it looks like I'll have that much time to get back to
hobby machining. Right now, I don't.


That's what I was thinking, it would be a nice thing to have if you had
the time and tools to make it, but you seem busy. Hopefully you get the
time and the opportunity to make one and prove its usefulness.

I hope, but I've decided I won't retire unless I become disabled. I
still enjoy my work too much. Today I've been interviewing subjects
for a sawing article.

--
Ed Huntress

On Mon, 12 Dec 2011 14:41:16 -0600, Jon Elson wrote:

On 12/12/2011 12:46 PM, Lloyd E. Sponenburgh wrote:

I made a really beefy (3" steel tube) boring bar, and found only that the
flex in my compound/cross slide is still too much to keep the bit from
singing excessively.
Yup, that was my worry. Only an insanely HUGE lathe would be stiff
enough to handle a boring bar with 15" overhang. I have a 3500-Lb
Sheldon 15" lathe, and I really doubt it could handle such a nasty
job properly.

Jon

https://picasaweb.google.com/gunnera...eat=directlink

Define "Huge"

This one is actually pretty small.

https://picasaweb.google.com/lh/phot...t=d irectlink


Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

Ed Huntress wrote:
On Mon, 12 Dec 2011 21:42:56 +0000, David Billington
wrote:


Ed Huntress wrote:

On Sun, 11 Dec 2011 23:21:37 +0000, David Billington
wrote:



Ed Huntress wrote:


On Sun, 11 Dec 2011 20:58:20 +0000, David Billington
wrote:




Joseph Gwinn wrote:



In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:





" fired this volley in news:7080e05e-
:




Since you do not have to end up with a hole of an exact size, I would
suggest line boring. But you have had a end cap welded on. So I am
kind of too late.




That would require building more tooling than the job is worth. Getting
that tube squared up on the tool rest, at the right height, and true end-
to-end would be a terrible amount of work.
(considered it, though! G)





I assume you are going to use a steady rest...............




Would, but mine won't open to 6.5".




It's fairly easy to cob one up from aluminum plate for a known diameter.






You might also see if you can get some aluminum hollow bar.




??? They're not precision-bored, either. This will end up being a
cylinder for a pasta extruder. (no... commercial air cylinders aren't
cost-effective, either ! G)





For honing I would look at flexible hones.




Just how good does this need to be, to extrude pasta?

One classic dodge I read about in old machining books was to attach the
workpiece to the carriage and mount a long boring bar between centers of
the lathe. The bit is in the center of the bar, perpendicular to the
bar axis. One moves the carriage to machine the bore.




I used that technique last year when I wanted to make some backing bars
for a pipe bender and had no other practical way of machining a
semi-circular channel about 10" (250mm) long to suit 1.5" nominal bore
pipe . The between centres boring bar was trivial as no great accuracy
was required so I just used a grub screw to clamp the cutter in a cross
drilled hole and set its position with the DRO. The larger part of the
project was making a T slotted table to go on top of the cross slide of
my Harrison M300. The M300 has a cross slide with a top like a dovetail
cutter for clamping tooling to, this seems to be a feature of more
recent 600 group products and seems to be used on some
Clausing/Colchester lathes as well. I worked very well and I can see the
T slot table being used for other things in the future. I can also see
that in Lloyd's case he would end up spending some time making suitable
brackets to hold the tubing to the cross slide.



T-slotted cross-slides, FWIW, are a British thing and go 'way back.
During WWII, when South Bends were made under license in the UK, they
made them with T-slotted cross slides. There was a company, either
here or in the UK, who made them available a couple of decades ago;
they were cast and had to be machined and scraped-in. I always wanted
one for my SB.




I didn't realise they were a British thing but my Kerry 1140
http://www.lathes.co.uk/kerry/page2.html has 2 slots as standard.


That looks like a very nice lathe.


I imagine it was a very nice lathe when new but I bought it used and
learned a few things about buying a lathe. Overall I think I didn't do
badly and it has done some good work. It's worn in the ways and the
headstock gears are noisy in the slower speeds but I keep it as I have
the space and I use it for things I wouldn't want to do on the much
better condition Harrison M300. Looking at the Kerry it would seem to be
a bit more heavily constructed than the Harrison even though only an
11" lathe as compared to the 13" of the M300. Having used the Kerry for
a number of years and now the M300 I sometimes find it odd to reach past
the chuck to the clutch on the back of the headstock on the Kerry
thinking what would I do if something went wrong and needed to stop it
as the M300 has the safety neurosis off foot bar and brake below the
bed. I also have this idea of raising the headstock and tailstock on the
Kerry on blocks to increase the swing as most of what I do with it these
days is metal spinning. I may do that about the same time as you do the
cross slide.



A mate
has a WWII era Southbend so the next time I'm over there I have a look
and see if it has a T slot cross slide . IIRC his father has shown him
how to do milling on the lathe so it's possible it has the T slots.


Yeah. I don't know if they made all of them that way, but I know that
was the source of some of them that wound up in the US in the early
'50s. I've seen a couple of old ones here.


What happens when someone sees one of those and doesn't realise it
wasn't made by Southbend in the US. I would imagine that could be the
cause of some heated arguments.


Oh, when they get that old, I don't think anyone gets excited about a
lathe's origins. The condition is everything.

BTW, I don't know if what I saw was actually British-made SBs, or just
the British-made cross-slides on a US-built lathe. As far as I know,
they were basically the same.

There also were some Bridgeport mills made by Beaver during the war. A
few of those are over here, too, if they haven't all been scrapped by
now. I don't know for sure if they were exact clones made under
license, but I think they were. In the years since, Beaver has
modified the old Bridgeport design.

I'd not heard about the war time Beaver production but a machinist I
used to know had 2 or 3 later Beaver mills and they seemed somewhat
more substantial than the usual J head BP as I have. One Beaver machine
he saved the mill from being scrapped without its head and fitted a BP M
head which looked a bit odd but he did good work with it when
required. That M head also got put on his large lathe at one point in
place of the compound and got used for milling a helical channel in a
thick walled tube for a hydraulic heat exchanger. Worked very nicely
from the results I saw when being machined.


Dan in the other response posted a source of the T slot Southbend cross
slide castings, do you still have the inclination to make one and if so
do you have the time?


Aha. Well, the issue now for me is getting the milling done, and the
total cost. I scrapped my milling machine this past summer (a 1917
Taylor & Fenn knee mill that was in need of scraping and lead screws,
or a new mill), and I haven't replaced it yet.

It's not something I'd use all the time but I used to make model steam
engines and it's really nice for line-boring and for some milling
jobs. If I get time, I'd like to make some IC engines. It might be
worth it if it looks like I'll have that much time to get back to
hobby machining. Right now, I don't.



That's what I was thinking, it would be a nice thing to have if you had
the time and tools to make it, but you seem busy. Hopefully you get the
time and the opportunity to make one and prove its usefulness.


I hope, but I've decided I won't retire unless I become disabled. I
still enjoy my work too much. Today I've been interviewing subjects
for a sawing article.

On 2011-12-12, Ed Huntress wrote:
On Sun, 11 Dec 2011 21:43:03 -0800 (PST), RS at work
wrote:

[ ... ]

I wonder if you made some sort of truss set up on the boring bar if
you could increase the rigidity of the boring bar to acceptable
limits? what I picture is your 3" pipe with a flange welded to each
end with some rods welded to one of the flanges and passing through
the flange on the other end, where you could pre-load the rods by
turning nuts.

Another idea would be to weld some "fins" along the axis of the pipe.

[ ... ]

I'm not good at the stiffness and strength values for various shapes,
but for a tube or round rod, the stiffness increases as to the cube of
the diameter. And a rod of a given diameter is only slightly stiffer
than a thick-walled tube of the same diameter.

And -- you can damp the vibration by filling the tube with lead
shot -- or even steel BBs. That way, it would not "sing" at you as
badly. (Or, if you have the patience -- fill it with concrete and wait
for it to set.)

The most efficient way to get greater stiffness, then, is to increase
the tube diameter. So a piece of water pipe of 3" or greater diameter
is likely the most cost-effective way to get adequate stiffness for
this job. You'd need at least a 3" diameter of steel for a 16" length,
and more is better.

Amen!

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Dec 12, 5:43*pm, Gunner Asch wrote:

Yup, that was my worry. *Only an insanely HUGE lathe would be stiff
enough to handle a boring bar with 15" overhang. *I have a 3500-Lb
Sheldon 15" lathe, and I really doubt it could handle such a nasty
job properly.

Jon



Define "Huge"


Gunner



Maybe not "Huge", but I think large enough. And way bigger than my
lathe.

http://www.carneymachinery.com/item_...entory_id=5245

Dan

On Mon, 12 Dec 2011 12:46:02 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Greetings Lloyd,
I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric
fired this volley in
:

It does wear out your fingers so holding a small piece of leather or
wearing a leather glove helps. I know this can be dangerous. I
probably wouldn't let someone do the above in my shop. But I do do it.


The problems with that are the following:

1) the "finger technique" works fine when you can grip the boring bar
fairly near the cutter. I do it all the time. It does not do much good
if you have to grip it 3/4-way back to the tool rest.

2) I'd have to reach about a foot into a spinning workpiece without being
able to clearly see my hand/fingers, and also would then have only one
hand left to run the machine (from an odd body position).

I don't think I'm quite ready for that. G

I have quite nearly given up on this workpiece. Although it will cost me
"an arm and a leg" (though not as quickly as the above method), I believe
I'm going to settle for the wait time to purchase a body tube for a large
pneumatic cylinder.

I made a really beefy (3" steel tube) boring bar, and found only that the
flex in my compound/cross slide is still too much to keep the bit from
singing excessively.

LLoyd

fired this volley in
:

I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric

The part isn't what's springing. I did my test cuts on a thin ring of
material solidly clamped in the chuck. I can assure you, it did not
contribute to the chatter I got.

"Fingering" the boring bar _did_ reduce the chatter to an almost-
acceptable level, but remember -- I've got a full 15" overhang on the
compound. That's _way_ beyond what's going to work on any lathe smaller
than (perhaps) a 36" swing.

I wasn't going to condemn a good piece of stock that I might use for
other purposes, just to do a test. The test piece was just a small drop
from a prior job.

The best solution is a "drill" made with adjustable followers that track
the surface of the cut as it proceeds. This is similar to the "packed
bit" principle used to bore cannon.

If I find a need to make more of these, I'll probably build a dedicated
boring device that is self-powered, and doesn't rely on my lathe's
rigidity to do the job. It's not complex... just a lot of work.

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com fired this volley in
. 3.70:

a thin ring of

make that a "short" ring. It was 3/8" walled material, so springing of the
work was not the issue.

LS

On 12/13/2011 11:35 AM, Lloyd E. Sponenburgh wrote:
fired this volley in
:

I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric

The part isn't what's springing. I did my test cuts on a thin ring of
material solidly clamped in the chuck. I can assure you, it did not
contribute to the chatter I got.

"Fingering" the boring bar _did_ reduce the chatter to an almost-
acceptable level, but remember -- I've got a full 15" overhang on the
compound. That's _way_ beyond what's going to work on any lathe smaller
than (perhaps) a 36" swing.

You can put a bag of shot in a hollow boring bar, or wrap it with a
resilient material and then a heavy material like lead sheet. There are
commercial boring bars with Tungsten bars inserted in the tool end.

Jon

On Tue, 13 Dec 2011 13:46:42 -0600, Jon Elson wrote:

On 12/13/2011 11:35 AM, Lloyd E. Sponenburgh wrote:
fired this volley in
:

I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric

The part isn't what's springing. I did my test cuts on a thin ring of
material solidly clamped in the chuck. I can assure you, it did not
contribute to the chatter I got.

"Fingering" the boring bar _did_ reduce the chatter to an almost-
acceptable level, but remember -- I've got a full 15" overhang on the
compound. That's _way_ beyond what's going to work on any lathe smaller
than (perhaps) a 36" swing.

You can put a bag of shot in a hollow boring bar, or wrap it with a
resilient material and then a heavy material like lead sheet. There are
commercial boring bars with Tungsten bars inserted in the tool end.

Jon

There are a number of boring bars MADE out of tungsten as well as
carbide


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On 12/13/2011 1:16 PM, Gunner Asch wrote:

[tedious bull****]

You're not long, gummer - Tavonnie told me she could barely find your
junk - but you're definitely a massively large bore - and boor.

On Tue, 13 Dec 2011 11:35:51 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
:

I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric

The part isn't what's springing. I did my test cuts on a thin ring of
material solidly clamped in the chuck. I can assure you, it did not
contribute to the chatter I got.

"Fingering" the boring bar _did_ reduce the chatter to an almost-
acceptable level, but remember -- I've got a full 15" overhang on the
compound. That's _way_ beyond what's going to work on any lathe smaller
than (perhaps) a 36" swing.

I wasn't going to condemn a good piece of stock that I might use for
other purposes, just to do a test. The test piece was just a small drop
from a prior job.

The best solution is a "drill" made with adjustable followers that track
the surface of the cut as it proceeds. This is similar to the "packed
bit" principle used to bore cannon.

If I find a need to make more of these, I'll probably build a dedicated
boring device that is self-powered, and doesn't rely on my lathe's
rigidity to do the job. It's not complex... just a lot of work.

Lloyd
Greetings Lloyd,
Sorry for the late reply. I understand that it's the bar that wants to
vibrate. In my experience I have been able to get the bar to deflect
and stay deflected while at the same time keeping the part from
vibrating by dampening vibrations using the above method. It really
can be hit and miss and I totally understand why you didn't use my
method this time. I usually only resort to holding my hand on stuff
and grinding the tool just so and turning things really slow with as
heavy a feed as allowed by the required finish when I really need to.
For a one or two part job needed now it's sometimes the best option.
But for production needs or when time and money allow other options
then the other options are used.
Cheers,
Eric