Boring on mill vs lathe - Blondihacks prompted this question

[The Metal Butcher]

Vastly prefer boring on the lathe. On the lathe, drop in my boring bar holder with boring bar already in, adjust length if required, bore. On the mill, gotta drop the tool you have, drop the knee, get out the boring head, get out the mill boring bars and get it all adjusted. In addition, you have to stop the spindle for every adjustment, unless you've got a nice De Andrea like Doozer.

I do tend to get very accurate results on the mill, possibly even more accurate. Typically within a thou on my Shars head. Dunno why, good luck I guess.

[rdfeil]

I do everything on the lathe.

Because, well, I don't have a mill.

This sounds like a perfect reason to get a mill 🤣 !!!!!!

[Doozer]

I have a milling machine with a Morse taper.
It won't bore even in aluminum without chatter.
So I used to avoid using it for such.
Then I discovered my Morse taper spindle
was bellmouthed from years of being used with
split collets. I did an experiment and wrapped
one layer of masking tape around the big end
of the Morse taper shank and installed the
boring head in the spindle. The chatter went
away. I think Quin has an even smaller mill than
my Bridgeport M-head. So I can see chatter
and small depths of cut can be a problem.
No wonder using a lathe for big holes is attractive.

-D

[Ringo]

why bother to center it up so much in the 4-jaw? It dont matter. waste of time to get all indicated on that first step.
Its a indicator holder. You set the zero wherever you want it. every time you use it it got a different zero place.
that first step is overkill

[chucketn]

.
But it does require a lot of knee cranking and uses a lot of vertical room. There is something to be said for a DTI when used with the proper holder. Either something like Quinn made or one like Stefan posted up plans for and which I gather is still out there.

..

Where are Stefan's plans posted?

Edit: Disregard, I found and printed the plans.

[BCRider]

I have a milling machine with a Morse taper.
It won't bore even in aluminum without chatter.
So I used to avoid using it for such.
Then I discovered my Morse taper spindle
was bellmouthed from years of being used with
split collets. I did an experiment and wrapped
one layer of masking tape around the big end
of the Morse taper shank and installed the
boring head in the spindle. The chatter went
away. I think Quin has an even smaller mill than
my Bridgeport M-head. So I can see chatter
and small depths of cut can be a problem.
No wonder using a lathe for big holes is attractive.

-D

She has mentioned and shown the limits of her mill on a number of occasions. I'm pretty sure that just using the coaxial indicator on a part in her vise is pushing the mill's vertical travel limit. And by extension it suggests that it would be a chatterbox when extended that far out to use for boring as well. I'm sure that had something to do with her decision.

Interesting what you found with the spindle. I can only imagine how that someone must have cinched down on the drawbar to create that much pressure. And what a job it would have been to knock it free.... Those poor bearings ! ! ! ! My first mill had an MT3 taper. It also came with a set of MT3 collets. I tried using them ONCE and was so put off by the Herculean effort needed to free up the collet that I never tried it again. Instead I made up my own lowest possible overhang solid end mill holders and just lightly pinched the drawbar to hold them in place.

Ringo, if it were me doing that job I'd center up the punch mark too. If for no other reason that it makes it easier and quicker later to use the scribe marks and just eyeball things for the shaping to the lines on the rotary table.

[Cenedd]

I'm pretty sure her mill is bigger than mine and mine will take a boring head (50mm if I remember correctly). It wasn't great with the supplied brazed carbide bars but seems better with the cut-down lathe boring bar fitted with an aluminium profile insert. Haven't used it in anger yet though.

With you on the MT3. In hindsight I'd have gone R8 but I didn't know, it wasn't an option where I was buying from and I believe it further reduces the limited Z height due to longer stick-out.
Mostly I use an ER32 collet holder but the MT3 collets do come in useful when you have to maximise available Z height. Disturbing quantity of "persuasion" required to free them though!

[J Tiers]

............................................. Disturbing quantity of "persuasion" required to free them though!

Not necessary!

Use an "ejecting" drawbar. Then a wrench easily pops the MT-whatever loose. No violence required, no bearings stressed.

There was an article maybe a dozen years ago detailing how it's done.

The short story is that a collar is screwed on the back of the spindle. When tightening the drawbar, it presses on the outside of the collar. When ejecting, it presses against the inside, and pops the MT out. All the force is contained within the spindle.

[Doozer]

Interesting what you found with the spindle. I can only imagine how that someone must have cinched down on the drawbar to create that much pressure. And what a job it would have been to knock it free.... Those poor bearings ! ! ! !

My spindle is worn from using spring collets for years.
It is a 1940s machine. Hoop stress and plastic deformation
were not the cause. It has a self releasing drawbar.
No one ever had to knock on the spindle.

-D

[Toolguy]

Also, if you put Cocoa Butter on the tapered part of the collet, it will grip tighter, and release easier, by reducing the amount of friction between the collet and spindle.

[Doozer]

I will never be putting any kind of butter on my spindle taper.
Never freaking ever.

-D

[Cenedd]

J Tiers
I suspect that it may have been yourself that was trying to explain one of those to me previously and I just wasn't getting it. Not that I'd probably have got round to making one yet at the glacial speed I get round to projects...let alone finish them! Mostly though I found that the merest smear of oil on the taper - and I'm just talking what will wipe off your fingers really - is enough to make most of the tapers come out with a tap rather than a beating. Doesn't seem to affect the transmission of torque either. The MT3 collets were particularly bad...but I don't think I've had occasion to use one since I did the conversion from tilting column to fixed that also give a little more height. It's no Bridgeport but it's better than it was

[Randy]

why bother to center it up so much in the 4-jaw? It dont matter. waste of time to get all indicated on that first step.
Its a indicator holder. You set the zero wherever you want it. every time you use it it got a different zero place.
that first step is overkill

She does tutorials. Part of her process is showing how to do things with precision, even if it's overkill in the moment. And if I were doing it I'd dial it in too, if only to get that warm & fuzzy feeling.

[jcge]

Boring in the lathe - the cutting forces (generally) are pushing the tool/workpiece in a single direction (+X, +Z) where the backlash is (generally) always taken up.
Boring in a (vertical knee) mill - the cutting forces are thrusting the workpiece/table in two axis alternately (eg +/- X and +/- Y) requiring the table be locked to prevent movement in backlash.

[The Metal Butcher]

Boring in the lathe - the cutting forces (generally) are pushing the tool/workpiece in a single direction (+X, +Z) where the backlash is (generally) always taken up.
Boring in a (vertical knee) mill - the cutting forces are thrusting the workpiece/table in two axis alternately (eg +/- X and +/- Y) requiring the table be locked to prevent movement in backlash.

I personally have never taken a heavy enough cut to sling a bridgeport table around at 660 RPM. The acceleration would be incredible. But, point taken.