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From: Cliff on 13 Jan 2007 09:36
On 13 Jan 2007 05:40:07 -0800, "Bo" <bo(a)tilikum.com> wrote:

>Titanium (alloys do differ) generally work hardens and that can make
>for some humongous forces and at some point you can exceed the ultimate
>strength and just fracture the metal.

Not a good idea to form/roll tap unless called out on the print
as allowed or approved *in writing* by the customer, usually.
The assumption UOS is for cut threads.
Not good for some materials either. Or certain
applications. Might be hard to control class of thread
too.

Great otherwise, though it may take more torque
than a cut thread to produce. <g>.
--
Cliff

From: Cliff on 13 Jan 2007 09:41
On 13 Jan 2007 06:28:43 GMT, D Murphy <spamto154(a)comcast.net> wrote:

>blind holes

Usually must be vented ... assure that any such roll/forming
tap has venting provision. Some do not IIRC.

HTH
--
Cliff
From: ff on 13 Jan 2007 15:43

"D Murphy" <spamto154(a)comcast.net> wrote in message
news:Xns98B74DE33A88BW12BU20MU38SY(a)130.133.1.4...
> "guynoir" <blpzx(a)hotmail.com> wrote in news:1168637968.158641.149870@
> 51g2000cwl.googlegroups.com:
>
>> I need to roll some threads in a blind hole in 6AL-4V titanium. They
>> are about 5/8" holes, about 5/8 deep. Anyone have some guidance on
>> how
>> to do this?
>
> If you have a choice, thread mill. Otherwise cut tap.

Good advice.


From: JKimmel on 15 Jan 2007 11:55
D Murphy wrote:

> It's a one pass operation.
>
> I don't have the pitch nor my technical data handy, but I'm guessing
> without a geared head spindle you'll need an honest 15-20 horsepower
> depending on the pitch. Or about 30-40 haaspower.
>
I found a picture of a roll forming tap. It was not what I thought, I
expected "rollers". It looks to me like you just drive a screw into the
hole and create threads that way. Now I understand why it takes so much
torque and why you need "venting".

Cut threads are not an option. It is a very high stress, very high
fatigue forged aircraft part: a helicopter tail rotor.

Thanks for all the excellent information, I may be asking for quotes.

--
J Kimmel
myname(a)whereIwork.com
www.metalinnovations.com

"Cuius testiculos habes, habeas cardia et cerebellum." - When you have
their full attention in your grip, their hearts and minds will follow.
From: Cliff on 15 Jan 2007 17:51
On Mon, 15 Jan 2007 08:55:27 -0800, JKimmel <myname(a)whereiwork.com> wrote:

>Cut threads are not an option. It is a very high stress, very high
>fatigue forged aircraft part: a helicopter tail rotor.

You may wish to check with their engineers.
Consider what happens if the required material flow to
produce the thread exceeds the material's ductility.
Consider the residual stress from such flow .... you just
stressed those threads in forming them. Was this good or bad
for the application?
Also consider stress & fatigue cracking in the material. Did
the forming process produce crack initiation sites/flaws?
You may also have increased inspection & certification costs.
But there may well be a spec that covers it. One way or another <g>.
--
Cliff
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