Re: [CAD_CAM_EDM_DRO] Helix Angle

Hi Terry:
You're going to have some difficulties with this setup.
The saw is planar, but the slot you hope to cut is not, assuming of course
that you really do want to make a helical slot and not just an angled slot.
To minimise this effect, choose a very small diameter saw, and the finest
pitch helix you can get away with.
How deep into the bar do you want to cut?
Cheers

Marcus
PS to draw the slot you have to have a 3D version of Autocad.
Create a cylindrical surface and project angled lines onto it.
Then rotate and translate the resulting splines as many times as you need to
to connect them all up as a continuous spiral.
Crappy workaround but it does work.
MC

----- Original Message -----
From: Terry Owens <terry@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, March 10, 2004 9:35 AM
Subject: Re: [CAD_CAM_EDM_DRO] Helix Angle


> Hi,
>
> Thank you for the replies but they don't help as everyone came up with a
> different answer.
>
> What I'm trying to do is cut a 3 start helical slot around an aluminium
bar
> to make couplings for stepper motors. The way I would machine them is to
> hold them in the lathe chuck and use a slitting saw in a milling spindle
set
> at the helix angle of the slot, which happens to be 8 TPI. This is easy to
> do, once I have the helix angle, but not very productive. As I wanted to
> manufacture a lot of these couplings, of different sizes, I have designed
a
> jig which consists of a screwed threaded bar which the part to be machined
> is locked to. The threaded bar is used to advance the part to a slitting
saw
> held in a horizontal miller but the jig must be set at the helix angle.
>
> All the machining is easy once I have the helix angle but drawing the slot
> in ACAD is a different matter. I tried to do it all day yesterday with
> results that didn't please me. I draw it the same way I machine it, not
> forgetting I got a different angle to all of the posts :-)
>
> As to the question why 18mm with an 8 TPI thread. I'm English and come
from
> that generation that had to learn measurements ambidextrously and as such
I
> think in imperial and draw in metric. I machine in either depending on the
> machines scales. Metal here can come as imperial or metric and one is
often
> sold for the other. If I order 3/4" I'll sometimes get 19mm or visa versa.
> The 18mm measurement was after machining a 19mm or 3/4" bar to 18mm.
>
> Anyway my question is still the same, which of us is right. The thread
I'll
> be using will be square or acme form.
>
> Regards,
>
> Terry