[modeleng] Re: Screwcutting
- From: Patrick Coppens <develop@xxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Sat, 24 Nov 2007 13:07:26 +0100
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
>>
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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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