On Sep 8, 6:26 pm, Jon Anderson wrote:
Anyone know of a source for aluminum bar in an octagonal
cross section? 5/16 or 9mm across flats, prefer 6061 to
insure anodize color match with a related part. I'm guessing
this is not available, haven't found anything via Google,
but thought I'd ask anyway.

Jon


Hex is easy- but octagonal?

Could take square and knock the corners off, but that's a fair bit of
removal.


Dave

Anyone know of a source for aluminum bar in an octagonal
cross section? 5/16 or 9mm across flats, prefer 6061 to
insure anodize color match with a related part. I'm guessing
this is not available, haven't found anything via Google,
but thought I'd ask anyway.

Jon

wrote:

Hex is easy- but octagonal?

Could take square and knock the corners off, but that's a fair bit of
removal.

It's for an ultra high tech carbon fiber violin bow,
octagonal profile matches the bow so hex won't cut it.
Options are octagon, knurl, or some sort of shallow fluting.
But not worth the time/expense of profiling the OD to get
the octagon.

(dang, wish my Omniturn had the indexing spindle!)

Jon

On Sep 8, 5:26*pm, Jon Anderson wrote:
Anyone know of a source for aluminum bar in an octagonal
cross section? 5/16 or 9mm across flats, prefer 6061 to
insure anodize color match with a related part. I'm guessing
this is not available, haven't found anything via Google,
but thought I'd ask anyway.

Jon

If you go to VarmintAls.com , I hope that URL is correct, click on his
Mini-Lathe page and scroll down to a direct link to Online Metals. I
was just browsing their site today and I am pretty sure I saw some Hex
or octagonal bar stock but I am not sure of the alloy number.


Dennis

On Mon, 08 Sep 2008 15:07:21 -0800, Jon Anderson
wrote:

wrote:

Hex is easy- but octagonal?

Could take square and knock the corners off, but that's a fair bit of
removal.

It's for an ultra high tech carbon fiber violin bow,
octagonal profile matches the bow so hex won't cut it.
Options are octagon, knurl, or some sort of shallow fluting.
But not worth the time/expense of profiling the OD to get
the octagon.

(dang, wish my Omniturn had the indexing spindle!)

Jon
========
You may want to contact the custom aluminum extrusion houses.
They may have a stock die for what you want, or for this simple a
profile it should be cheap to edm one. Be sure to check material
and physical properties/temper. A few places you can try
http://www.paramountextrusions.com/shapes.htm
http://www.zycon.com/Products/Alumin...Zin Aod5mgKjQ

web page showing octagons
http://www.argylein.com/extrudes.html
http://www.argylein.com/search_dies-n.php?words=OCT


google on octagon "aluminum extrusions" for c. 700 hits.
register on
http://www.globalspec.com/MyGlobalSp...rID=-136104688
for a bunch more.

On Sep 9, 12:33*pm, Jon Anderson wrote:

Think I've figured out an approach though, will just chamfer
mill short lengths of material in the mill, then turn. Not
the most efficient approach, but it's a low volume high
value part that would certainly justify it.

Jon

For short lengths a 5C spin index should work well.

TwoGuns wrote:

I am pretty sure I saw some Hex or octagonal bar stock but I am not sure of the alloy number.

Thanks, I tried all the online sources I could think of,
nobody has it. Funny though, lots of places list weight per
foot for octagon materials, nobody supplies it....


Jon

F. George McDuffee wrote:

You may want to contact the custom aluminum extrusion houses.

Only problem with extruders is the minimums. A single 20'
length would be a several year supply. And there are two
other sizes I need to make. A 1000lb order which is a common
min. order would last for several centuries! Customer is not
unwilling to invest, but probably not for inventory that
will outlast him and his kids.... G

Think I've figured out an approach though, will just chamfer
mill short lengths of material in the mill, then turn. Not
the most efficient approach, but it's a low volume high
value part that would certainly justify it.


Jon

On Tue, 09 Sep 2008 09:54:19 -0800, Jon Anderson wrote:

Jim Wilkins wrote:

For short lengths a 5C spin index should work well.

The entire length of the finished part is octagonal. Yes, I
could make it out of round stock in this manner, but then
would have to move to the lathe to part off, or hack saw
off. While quantities are low by production standards, I
could be making up to 100 pcs in each of three different
sizes, and that would be a big pain. Also, we're looking at
multiple grooves, or finning, just as a way to reduce
weight. If the part was already to length it would require
handling twice, turning the part around in the collet.
If I had an 8" length, I could proceed to make the part
complete in one smooth process. I'd just be changing 'bars'
a lot more often that I'd originally wanted to.

For perspective, this is for a high tech violin bow made
from carbon fiber. Customer is going to the expense of
buying 5-40 threaded titanium screws from Germany and having
me make as light an aluminum knob for the end as we can, all
to shave another gram or so. It's a production process, the
focus is on end results, not cost. Yet, we don't have
anywhere near the volume to justify custom extrusions.

Appreciate the input though!

Jon

Anneal and press the round stock through a hex hole in hardened steel.

Jim Wilkins wrote:

For short lengths a 5C spin index should work well.

The entire length of the finished part is octagonal. Yes, I
could make it out of round stock in this manner, but then
would have to move to the lathe to part off, or hack saw
off. While quantities are low by production standards, I
could be making up to 100 pcs in each of three different
sizes, and that would be a big pain. Also, we're looking at
multiple grooves, or finning, just as a way to reduce
weight. If the part was already to length it would require
handling twice, turning the part around in the collet.
If I had an 8" length, I could proceed to make the part
complete in one smooth process. I'd just be changing 'bars'
a lot more often that I'd originally wanted to.

For perspective, this is for a high tech violin bow made
from carbon fiber. Customer is going to the expense of
buying 5-40 threaded titanium screws from Germany and having
me make as light an aluminum knob for the end as we can, all
to shave another gram or so. It's a production process, the
focus is on end results, not cost. Yet, we don't have
anywhere near the volume to justify custom extrusions.

Appreciate the input though!

Jon

Try this site

http://www.speedymetals.com/default.aspx


--
Bruce

"You know that old Beach Boys song, Bomb Iran? Bomb bomb bomb, bomb bomb
Iran."
John McSame , More Bush in more places!!!

For short lengths a 5C spin index should work well.

The entire length of the finished part is octagonal. Yes, I
could make it out of round stock in this manner, but...

I was thinking he meant with a square collet. Actually, with a square
collet, you may not even need a spin index, just a square collet
block, and mount the collet in the block at 45 degrees...
--Glenn Lyford

wrote:

I was thinking he meant with a square collet. Actually, with a square
collet, you may not even need a spin index, just a square collet
block, and mount the collet in the block at 45 degrees...

That would require indexing the collet to get the stock at
the 45 degrees. Starting with round stock means more passes
but much lighter cuts. It still leaves me with either a part
I have to handle twice in the lathe to do the grooving, or
waste a significant bit of material leaving extra in the
collet. Though low production, it's still a production
process and flipping a collet block 400 times gets tedious.

Jon

On Wed, 10 Sep 2008 06:37:09 -0800, Jon Anderson wrote:

wrote:

I was thinking he meant with a square collet. Actually, with a square
collet, you may not even need a spin index, just a square collet
block, and mount the collet in the block at 45 degrees...

That would require indexing the collet to get the stock at
the 45 degrees. Starting with round stock means more passes
but much lighter cuts. It still leaves me with either a part
I have to handle twice in the lathe to do the grooving, or
waste a significant bit of material leaving extra in the
collet. Though low production, it's still a production
process and flipping a collet block 400 times gets tedious.

Jon

Hey - if it's fairly soft aluminium and you have a good-sized lathe, press
an octagonal die over the stock with the tailstock. Drill, thread, press,
cut, all with one instance of work-holding.

How much is he going to sell these bows for? My sister told me how much
her hi-end bow was once and it made my eyes open *quite* wide.

On Sep 10, 8:07*am, " wrote:
For short lengths a 5C spin index should work well.

I was thinking he meant with a square collet. *Actually, with a square
collet, you may not even need a spin index, just a square collet
block, and mount the collet in the block at 45 degrees...
* --Glenn Lyford

You can only rotate the collet if you move the guide pin.

I chuck round stock in a 3 jaw chuck with a 5C mount and move it back
and forth between the lathe and mill as needed.

On Wed, 10 Sep 2008 06:37:09 -0800, Jon Anderson
wrote:
snip
That would require indexing the collet to get the stock at
the 45 degrees.
snip
=======
If you have some sort of mill with the required travel, the
easiest thing might be to do two pieces at a time.
Clamp/indicate a straight piece of bar stock on your mill table
[even a Bridgeport should do fine no cnc necessary] and clamp two
pieces of square aluminium against the guide, and run a 90 degree
included angle endmill between the two pieces. Rotate stock 3
times.
For sample end mill see
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32

Good luck and let the group know how you make out.

On Sep 8, 4:26*pm, Jon Anderson wrote:
Anyone know of a source for aluminum bar in an octagonal
cross section? 5/16 or 9mm across flats, prefer 6061 to
insure anodize color match with a related part. I'm guessing
this is not available, haven't found anything via Google,
but thought I'd ask anyway.

Jon

You COULD set up a mini-rolling mill to produce the cross section you
need, my guess would be that you could use rollers maybe 3-4" in dia.
with the desired cross-section cut in them and T0 hardness stock.
Oven treat afterwards. Would save a lot of mill time if it'd work.

Stan

_ wrote:

How much is he going to sell these bows for? My sister told me how much
her hi-end bow was once and it made my eyes open *quite* wide.

I don't know, but they will not be cheap. My customer has
dome something really new. The bow is fully instrumented.
Pressure transducers on the string can resolve if the bow is
canted, and where the bow string is in contact with the
violin strings. In addition it carries 3 axis accelerometers
that resolve the actual 3D motion of the bow in real time.
Don't know what software he's doing this with, but he has a
solids model of the bow, hooking up the bow to the computer,
you can wave the bow around and watch the solids model
perfectly mimic the real bow.

I'm looking forward to seeing this thing in action in
mid-January, I'll better understand exactly what it can do.
But apparently through software there are a ton of things
you can do to the sound based on what the bow is doing.

I've been working with him on the frog adapters (where they
get these strange names I don't know), they are aluminum and
milled to relieve as much mass as we dare. There's going to
be three models, violin, cello, and bass.

He was in Ireland a couple weeks ago, some world class
violinist from Finland played with it and pronounced it
'historic'. It's first public performance debut is coming up
in San Diego in a few weeks or so, and it's also going to be
featured at some supercomputer convention.

I am playing a minute part in this, but it's neat to be part
of something that's really ground breaking. I'll ask him if
he has a web page on it yet and if I can post a link to it.


Jon

F. George McDuffee wrote:

If you have some sort of mill with the required travel, the
easiest thing might be to do two pieces at a time.
Clamp/indicate a straight piece of bar stock on your mill table
[even a Bridgeport should do fine no cnc necessary] and clamp two
pieces of square aluminium against the guide, and run a 90 degree
included angle endmill between the two pieces.

That's the approach I've settled on, except I'll do one bar
at a time down one side and back the other, rotating 180
just once. I have dual vises and custom jaws for machining
long lengths.
I'll post a link if my customer says it's OK.

Jon

Ok, this is what the octagon stock is for:

http://www.beamfoundation.org/media/KBow_NIME.pdf

2nd page shows the electronics and housing. Just above the
K-Bow legend is the frog adapter that I make. It's hollowed
out as much as we can get away with and fits over the
octagon shaped carbon fiber bow.

The octagon part I'm looking to make is at the end of the
adjusting screw. I was given the option of knurling this,
but even with a CNC grade knurling setup, I find getting
good knurls to still be something of a dark art. I can
produce knurls acceptable for most needs, but we're looking
at a high dollar item here, in market where craftsmanship is
still highly valued. Sticking with the octagon shape
maintains some tradition. I will be machining multiple
grooves mainly for weight reduction, though it will put a
high tech edge on the traditional shape.

Back up on the URL to the base site and there is an embedded
video link of it in action. I don't have quicktime installed
so haven't been able to view this myself yet.

Jon