If reduction of the work diameter is the goal, the Compound setting
should be 30.53 degrees off the axis of the Spindle.
HTH, Ralph
--- In 7x12minilathe@..., "imbrewster2" <ibrew@...> wrote:
That would also give a measurement of how much you are reducing the
diameter of your work.
Brewster
--- In 7x12minilathe@..., "David Thompson"
<dvaid2526@> wrote:
I agree, cutting at a 29 degree angle greatly reduces the stress
on the
tool. BTW many machinist leave their compound set on 29.5 degrees
because
during normal turning operations using the compound to advance
the
tool,
advances the tool .0005 for every .001 mark moved giving a little
more
accurate adjustment for final passes.
Dave
From: "born4something" <ajs@>
Reply-To: 7x12minilathe@...
To: 7x12minilathe@...
Subject: [7x12minilathe] Re: About cutting threads
Date: Mon, 26 Feb 2007 06:58:28 -0000
Ah, thanks for that Chuck.
That makes emminent sense. I was passing on what I'd been told
but
I'm NOT a formally trained or experienced machinist and the chip
issue makes a lot of sense. I guess my other angle comments re
Whitworth, etc. stand?
Funny. In some ways forums can result in a lot of newbies sharing
ignorance. However, some truths are self authenticating as the
picture builds up. I'll now go and watch those chips more
closely -
through the obligatory safety specs. I'm here to learn! Thanks
for
that link too.
Thanks again,
John
--- In 7x12minilathe@..., "Charles E. Kinzer"
<ckinzer@> wrote:
The main reason for the 29 degree angle (actually
conventionally
29.5 degree ) is to solve a chip problem, although there are also
other reasons. If you go straight in (radially) to cut threads,
the
metal removal from two equally cutting edges pushes the metal to
a
point where they both try to share the same space and it forces a
sort of goofy V shaped chip. The size of the machine has
nothing
to
do with it and I would certainly not characterize as a "cheat" so
much as good practice.
This is a site I found awhile back for a similar discussion on
another group and it has a pretty good discussion and diagrams on
thread cutting.
While it says that "radial infeed...is probably the most
common...also the least recommended", I don't believe I have ever
worked with a machinist that cut threads that way regardless of
how
large the machine is.
Chuck K.
----- Original Message -----
From: born4something
To: 7x12minilathe@...
Sent: Sunday, February 25, 2007 9:51 PM
Subject: [SPAM] [7x12minilathe] Re: About cutting threads
Hi Ian,
ATS? I need more acronyms - what's that one?
IMHO, the angle cheat isn't needed if you have a big solid
machine
with lotsa grunt. AFAIK it's a small scale machinist trick
to
eek
the best out of small machines.
Also, finishing with a die (hopefully) provides a smoother
bottom
fillet radius in the thread - at least, smoother than my HSS
grinding permits. A smoother radius means less stress
concentration
and a stronger end product.
John
--- In 7x12minilathe@..., "steam4ian"
<fosterscons@>
wrote:
>
> G'day Kevin.
> Take small cuts. There is no shame in finishing with a die
nut,
the
> professionals do.
> The 29 deg. compound setting is not something I learned
in
the
ATS,
> we just drove straight in. Used HSS tools on tough forged
bolts
> without problems.
> One good turn deserves another.
> Regards,
> Ian
>
> --- In 7x12minilathe@..., "born4something"
<ajs@>
> wrote:
> >
> > If you're gonna use this technique (and it's a venerable
technique)
> > note the cross-slide reading and back it out before
reversing.
> After
> > reversing, return the cross-slide to that position
(remembering
> > backlash - only read positions cranked inwards).
Finally,
advance
> > the tool further into the thread for the next pass by
using
the
> > compound.
> >
> > If you don't back the tool out you'll have the tool rub
all
the
way
> > back up the thread in reverse due to both work and
toolpost
spring-
> > back.
> >
> > John
> >
> >
> > --- In 7x12minilathe@..., Kevin Jones
<krjone01@>
> > wrote:
> > >
> > > > Also is there a trick to using the threading dial?
Mine
> doesn't
> > rotate.
> > >
> > > As mentioned before, you need to adjust it so that
gear on
the
> > back
> > > is turned by the threads (actually one very long worm
gear) on
> the
> > > lead screw. However, since the 7x lathes can be run in
reverse,
> > you
> > > really don't need to use it. Just never release the
half
nuts,
> and
> > > the run the lathe in reverse to return the carriage to
position
> > for
> > > the next cut.
> > >
> > > Regards,
> > > Kevin Jones
> > > Louisville, KY
> > >
> >
>
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