Re: [CAD_CAM_EDM_DRO] cnc lathe - threading - alternitive method?????

I have a friend that has several small H&G die heads set up on some of my
old Brown & Sharp single spindle screw machines, that make little brass
screws all day long. They make over 50,000 screws a month. They have these
machines running balls to the wall. They use rubber bands around the handle
to close the die. They are only open for an instant, just enough time for
the die to open and clear the length of threads before it snaps closed again
ready for the next operation. These are cam operated machines. The cams
are designed to move the die very quickly.

I don't know that much about cnc yet but I am learning and I am sure that a
cnc machine could be set up the same way. It would depend upon the machine
itself and of course the length of thread.

Going back to the years that I ran single and multi spindle screw machines
we did many unconventional things to get the machines to do what we wanted.
I could even see a micro switch operating an air valve, connected to an one
way air cylinder with a bleeder valve to allow the air to bleed off and the
cylinder to reset itself, that would close the die set as it was cycled,
this would allow more time to clear a longer thread. Sigh! But then maybe
such primitive methods are not allowed on cnc machines.

Just my 2 cents worth

Bruce

-------Original Message-------

From: CAD_CAM_EDM_DRO@yahoogroups.com
Date: 02/02/05 12:33:54
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] cnc lathe - threading - alternitive
method?????

How about mounting a thread die on the toolpost with a holder
that floats in the Z some. Kind of like tapping in a CNC mill.
For a regular die you would have to stop and reverse the spindle
to backup over the thread just cut. Or there's a die holder
called Geometric that, when the feed stops in the Z, will open
the thread chasers so it can be pulled off of the part without
stopping or reversing the spindle. Proble with these is that
they have a little handle that you have to pull to close the
chasers to cut the next thread.

All of this would be a bit iffy and you'ld have to tweak on
things to get it to work but it might be doable.

Adding a little spindle index detector and using TurboCNC is
still probably the easiest way to do it though.

Drew

Jon Elson wrote:

> Russ Waters wrote:
>
>
>>Hi to the group..... I need to pick your brain on this one!
>>
>>I would like to come up with a alternitive method of threading with a cnc

lathe,,,,, not using a feedback system with conjuntion of the G33 code, but
would it be possible to cordinate the spindle speed with the feedrate of the
z axis to do threading? I think it could be done, has anyone tried this,
or have a theory on how it could be done????

>>
>>
>
> Yes, but....
>
> The problem is that there will be no precise relation between the
> spindle and
> the Z axis feed, so the thread will be an APPROXIMATION of the desired
> thread
> pitch! If your spindle speed were held within 10%, then you'd get a
> thread pitch
> that was somewhere within 10%. So, for a 32 TPI pitch, you'd get
> something within
> 29 and 35 TPI. IS that good enough? I suspect not, for most purposes.
>
> Secondly, you would have no way to make multi-pass threads. Every
> thread would
> have to be cut in a single pass. Think you can cut an 8-TPI thread in
> one pass?
> Hmmm, I'd like to see your lathe!
>
> So, these are the reasons why feedback is used.
>
> Jon
>
>
>
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