Subject: Re: Boring holes

From: [email-masked] (Michael J. Edelman)
Date: 22 May 1995 11:57:50 GMT

[email-masked] wrote:
: Have a question: is it better to bore an accurate hole using a boring 
: head in a vertical milling machine, or is it better to bore the hole 
: using a boring bar in a lathe? Your views shall be welcomed.

The boring bar, being supported at both ends, *should* be more rigid...all 
things being equal. Of course, all things generally aren't equal ;-)

It really depends upon exactly what you're trying to do, and the accuracy 
you need.

--mike

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From: [email-masked] (Jon Gellman)
Date: Mon, 22 May 1995 14:21:59 GMT

>The boring bar, being supported at both ends, *should* be more rigid...all
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>It really depends upon exactly what you're trying to do, and the accuracy

What type of boring bar might that be? I've never heard of it. The usual kind
sticks into the work from the toolpost alone, and can flex and magnify any
slop in your lathe, especially if its small and old like mine. My 6" bar is 7/16
dia. which means that on deep bores I can take only shallow cuts, lest the
tool bend away from the work.  Most boring head bars aren't that long, but
the whole arangement is less inclined to that form of innaccuracy. Of course
the runnout on your mill and the state of the bearings come into play, not to
mention the humidity and phase of the moon. Mike's last statement is really
the bottom line in a situation with infinite variables.

Jon

Jon Gellman Effects
[email-masked]
NYC, NY

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From: [email-masked] (Michael J. Edelman)
Date: 22 May 1995 19:16:16 GMT

Jon Gellman ([email-masked]) wrote:
: [email-masked] (Michael J. Edelman) wrote:
[snip]
: >The boring bar, being supported at both ends, *should* be more rigid...all
: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
: >things being equal. Of course, all things generally aren't equal ;-)
: >
: >It really depends upon exactly what you're trying to do, and the accuracy
: >you need.
: >
: >--mike

: What type of boring bar might that be? I've never heard of it. The usual kind
: sticks into the work from the toolpost alone, and can flex and magnify any
: slop in your lathe, especially if its small and old like mine. M

There's also the type that is turned between centers, with the work held
rigidly on the carriage. I should have been more specific.

--mike

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From: [email-masked] (Ron Metcalf)
Date: 23 May 1995 07:17:17 GMT

In article <[email-masked]>, 
[email-masked] says...
>
>Have a question: is it better to bore an accurate hole using a boring 
>head in a vertical milling machine, or is it better to bore the hole 
>using a boring bar in a lathe? Your views shall be welcomed.

IMHO, in most cases, I'd perfer using a lathe. The set-up in generally 
more rigid ( with a mill, you also have to be concerned about quill 
extention, tool extention ( easier to control in lathe), etc).

---

From: [email-masked] (gary preckshot)
Date: 23 May 1995 19:54:41 GMT

> using a boring bar in a lathe? Your views shall be welcomed.

If I had a large irregular hunk of metal that I couldn't chuck but I could
clamp on my mill, I'd bore it on my mill.  On the other hand, if it was
round, fit in my 6" chuck, and I wanted the hole more or less on center,
I'd chuck it in my lathe.  If I wanted the hole off-center, or I wanted
several holes in strict relation to each other, I'd do it in the mill.

The essence of being a good machinist isn't being a dumb ox who, once
somebody else has planned out the sequence and setups, stands there and
produces a hole.  The essence is planning the strategy so that what would
have been an iffy operation is possible, and can be done accurately.  Your
question has no pat answer.

G.