[modeleng] Re: Screwcutting

It is possible to so mount the threading tool whereby
the cut can be made FROM the shoulder TOWARD the
Tailstock, eliminating the possibility of a crash.

Al
--- Patrick Coppens <develop@xxxxxxxxx> wrote:

> Ron Head wrote:
> > Hi Patrick
> >
> > The retractable toolholder is a nifty device, but
> the only benefit seems to 
> > be that you don't have to remember the tool
> setting at each pass.  You still 
> > have to be quick to disengage the leadscrew at the
> end of the cut.
> >
> > When I'm screwcutting, I like to make an undercut
> at the end of the thread, 
> > for the tool to run into.  I also run the lathe at
> a fairly slow speed, to 
> > give me sufficient reaction time!
> >
> > Which brings me onto one of my big grumbles with
> the Myford lathe.  The 
> > leadscrew engagement lever is on the left of the
> saddle, which means that 
> > when you are holding the lever and getting ready
> to disengage, you have to 
> > put up with hot swarf bouncing off the back of
> your hand!  Why they couldn't 
> > put it on the right, I'll never know.
> >
> > Regards
> > Ron
> >
> > ----- Original Message ----- 
> > From: "Patrick Coppens" <develop@xxxxxxxxx>
> > To: <modeleng@xxxxxxxxxxxxx>
> > Sent: Saturday, November 24, 2007 9:19 AM
> > Subject: [modeleng] Re: Screwcutting
> >
> >
> >   
> >> I find, that one of those retractable tool
> setups, an invaluable aid.
> >> I saw the principle on the "Hemingway Kits"
> website.
> >>
>
http://www.hemingwaykits.com/acatalog/Retracting_Tool_Holder.html
> >> The principle is almost silly in its conception!
> >> I have "improvised" one to try it out, and now,
> it is on my to do list
> >> to make
> >> a proper one, by next spring. It is especially
> helpful on the more
> >> economical lathes, where
> >> a dead stop system is difficult or impossible to
> use.
> >>
> >> It is a project, that can be adapted for all
> lathes, and will help anybody
> >> to overcome the fear, of not being fast enough,
> in retracting the
> >> cutting tool, and thus creating
> >> bedlam, if the cutting tip, digs itself in the
> chuck!
> >>
> >> Patrick
> >> Flanders
> >>     
> > MODEL ENGINEERING DISCUSSION LIST.
> >
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> >
> >
> >   
> Ron,
> 
> It is indeed true, that the prime feature of the
> device would be the 
> "nancy-ing" about with the dials, that can be
> omitted.
> But I find, that even the improvised version of the
> tool, gives me just 
> that much extra time to stop the lathe.
> Indeed this will not wash for all shapes and sizes
> of pieces to be 
> threaded, but in a sufficient amount of cases, I
> find that
> this type of set up,gives me some extra reassurance.
> As far as making an undercut goes ; yes it is a
> handy practice, but then 
> again in some cases that wouldn't be possible or
> desirable.
> 
> All is well, as long as you work with a lathe, that
> actually has two 
> half nuts! (contrary to the complete nut that is
> trying to work it!) and 
> an indicator!
> My big lathe, has that feature, but my small 7*12
> doesn't.
> I do most of my screw cutting in the small one
> however, as it has the 
> handy feature, of an electronic reverse.
> And with this tool, you only have to advance the
> cutter by how ever many 
> x/10 th you want your next pass to be, and providing
> you
> are not cutting strait up to a shoulder,and remember
> to retract the 
> lever when you are at the end of the cut.
> 
> I am however thinking about an electronic stop, that
> somehow slides on a 
> guide , covering, say the first half of the bed.
> The problem there is, that even when the lathe is
> spinning at low revs, 
> it does at least 1/2 if not 3/4 of a revolution,
> before it is completely 
> still.
> If I disengage the feed, then I loose my
> positioning, and that is why I 
> use the setup discussed, to give me that extra bit
> of time.
> 
> 
> Regards
> Patrick
>  
> 
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> 
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> 



      
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