On 2010-02-03, danmitch wrote:
DoN. Nichols wrote:

On 2010-02-02, danmitch wrote:

[ ... ]

There are some Aloris holders which might make a difference, if
you are willing to work with insert tooling.

First -- consider the following toolpost:

http://www.aloris.com/index.php/pages/Qualified%20Super%20Precision.html

which has *three* dovetails instead of two allowing work closer to a fat
live center in the tailstock.


[ ... ]

Note that I already have a HUGE collection of odd custom toolbits and
"Armstrong" style tool holders with various angles to choose from. Thus
some one of these is probably very close to what I need for any application.


The existing collection of Armstrong style tool holders makes a
difference. The only ones which I have are for the little
Atlas/Craftsman 6x18" lathe.

[ ... ]

I realize that there are some other more elaborate quick-change posts
that allow intermediate settings, and might solve some of this problem,
but that's not what I have.


Also -- some more elaborate tool holders for the simple Aloris
style quick-change toolpost -- as shown above.

[ ... ]

I'll agree with most of what Don states above, with the following
observations ...

My toolpost is a Phase-II "BXA" sized dovetail post.

As is mine -- the wedge style, FWIW. The reason that I
explicitly mention the Aloris toolpost is to call attention to the one
with three dovetails, to increase the flexability. This I would like to
have, but probably can't afford as a hobby machinist.

But all of the exiting tool holders which I pointed out will
work nicely on my Phase-II Series 200 (their designation for BXA).

It is completely
satisfactory on the Rockwell 14" lathe I have at the university. I have
a similar "AXA" size post on my Logan 10" at home.

O.K.

Yes, I have lantern toolposts and extensive sets of Armstrong-style tool
holders and bits for both lathes at both locations. This *IS* important
for my original argument. For most of my odd jobs I will already have
some tool/holder combination that is close to what I need. Perhaps only
some minor regrind is necessary, if that.

Without the above collection of tooling, in most cases the work could be
done by setting the quick-change toolpost to some odd angle and
custom-grinding some weird toolbit (this can take considerable time, and
may require a non-common toolbit (extra long, etc.). Switching to the
lantern post and existing tooling is often much quicker.

O.K.

[ ... ]

Some of the specialized Aloris toolholders Don mentions would certainly
assist in solving some problems. Sadly, the Aloris items are fairly
expensive, and our department budget usually requires a cheap, of time
consuming, solution. We're often "long on time and short on money".
Phase-II doesn't offer nearly the variety in low-cost toolholders. I've
made a few special holders for the Phase-II post (that hold tool bits at
odd angles) that are useful.

O.K. I've seen holders for other systems which hold the tools
at strange angles.

Some of the work I need to do involves machining (often INSIDE) complex
shaped existing vacuum fittings and chambers and such.

So -- not only are the workpieces strange in shape, but also
usually stainless steel to survive the bakeout prior to high vacuum
work.

Cutting
additional O-ring grooves or adding/altering ports are such
applications. These structures are fabrications, customized for various
research applications, and often have odd protrusions either inside or
outside. Often these things are not well planned, but just 'grow' as the
project develops. New ports are added, or fittings silver-soldered on.
Old ports get plugged (not always neatly). THEN somebody wants further
modifications. Just getting into the thing, or around the obstructions,
is usualy the problem.

O.K. This is something which calls for using whatever will
work, and not a problem which I normally encounter.

Tooling to do this often requires a long reach and strange angles.
Sometimes a boring bar, sometimes used as an EXTERNAL toolholder, is the
answer.

O.K. The Aloris style boring bar holders can be a good start on
this, with the lantern style toolholder at the end of the bar.

Sometimes a lantern post is the solution. In either case, a long
reach is often needed, with corresponding lack of rigidity. Light cuts
with sharp tools are a necessity. As is often the case, one spends 95%
of the time on the setup, and 5% making the cut.

Understood.

Such problems rarely arise when making new items.

Which is what I normally do -- so your case is extreme, but may
apply for others here too.

Since I don't have the collection of Armstrong type holders,
going to the toolpost would represent a significant expense for me, just
to get the holders. And that is money which I would rather put into
getting one of the adjustable angle Aloris insert holders.

Enjoy,
DoN.

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