If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those
sorts of volumes, and if I can get this below the $13 that the one
online machine shop I tried wants. I'm also not sure of where I can
compromise on specs to get the price down (the "D" probably has to be +0
- 0.005", the shaft can probably vary +/- 0.005", since it'll be running
in plastic bearings).

Any guidance appreciated.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

"Tim Wescott" wrote in message
...
If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch diameter,
mill finish, with one end turned down to 4mm with a 1mm flat (to make a
"D" 4mm diameter and 3mm from flat to round), about 5mm or so long, with
the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those sorts
of volumes, and if I can get this below the $13 that the one online
machine shop I tried wants. I'm also not sure of where I can compromise
on specs to get the price down (the "D" probably has to be +0 - 0.005",
the shaft can probably vary +/- 0.005", since it'll be running in plastic
bearings).

Any guidance appreciated.

Do you know Dave Corgill? ("Why") I'd give him a call. He runs old Brownies
that might, or might not, have the capacity to handle those shafts. The
flats are something he'd probably do on his mill.

We did lots of simple jobs like that in an old manual-machine shop I worked
in, and they were mostly done in two setups. One setup with a CNC mill/lathe
may not be the most economical way to do it.

Dave's phone is 214-741-9062. He rarely answers; leave a message. His wife
passed away a few weeks ago, and I don't know if he's in gear yet or not.
But he's your man for shafts with second operations.

--
Ed Huntress

Ed Huntress wrote:
"Tim Wescott" wrote in message
...
If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch diameter,
mill finish, with one end turned down to 4mm with a 1mm flat (to make a
"D" 4mm diameter and 3mm from flat to round), about 5mm or so long, with
the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those sorts
of volumes, and if I can get this below the $13 that the one online
machine shop I tried wants. I'm also not sure of where I can compromise
on specs to get the price down (the "D" probably has to be +0 - 0.005",
the shaft can probably vary +/- 0.005", since it'll be running in plastic
bearings).

Any guidance appreciated.

Do you know Dave Corgill? ("Why") I'd give him a call. He runs old Brownies
that might, or might not, have the capacity to handle those shafts. The
flats are something he'd probably do on his mill.

We did lots of simple jobs like that in an old manual-machine shop I worked
in, and they were mostly done in two setups. One setup with a CNC mill/lathe
may not be the most economical way to do it.

Dave's phone is 214-741-9062. He rarely answers; leave a message. His wife
passed away a few weeks ago, and I don't know if he's in gear yet or not.
But he's your man for shafts with second operations.

--
Ed Huntress


I guess it depends on how fast you can pump them through the machine vs.
how much time it takes to do the second operation on a second machine.

I could see this going pretty fast on a manual machine -- in fact I may
end up doing some of the work on a CAC* machining center. But I don't
really have a good enough mill to do this reasonably fast, and my lathe
is barely up to it.

* Cranky Adolescent Control

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

My son would be interested IF you don't have super short lead times. He's
working weekends in my shop to pay off debts. We'd do the turning on a
hardinge CHNC and the second op on a CNC knee mill sitting right beside.

On a job like this, the cost is all setup. You'll pay about the same for 10
parts as 100.

Email off list with prints, if interested.

Karl

On Sat, 30 Aug 2008 14:52:10 -0700, Tim Wescott
wrote:

If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Misumi?
https://fa.misumiusa.com/gwos/catalo...EGORY_I D=006
https://www.misumiusa.com/PDFViewer....e2008&Page=557

--
Ned Simmons

"Tim Wescott" wrote in message
...
Ed Huntress wrote:
"Tim Wescott" wrote in message
...
If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those
sorts of volumes, and if I can get this below the $13 that the one
online machine shop I tried wants. I'm also not sure of where I can
compromise on specs to get the price down (the "D" probably has to be
+0 - 0.005", the shaft can probably vary +/- 0.005", since it'll be
running in plastic bearings).

Any guidance appreciated.

Do you know Dave Corgill? ("Why") I'd give him a call. He runs old
Brownies that might, or might not, have the capacity to handle those
shafts. The flats are something he'd probably do on his mill.

We did lots of simple jobs like that in an old manual-machine shop I
worked in, and they were mostly done in two setups. One setup with a CNC
mill/lathe may not be the most economical way to do it.

Dave's phone is 214-741-9062. He rarely answers; leave a message. His
wife passed away a few weeks ago, and I don't know if he's in gear yet or
not. But he's your man for shafts with second operations.

--
Ed Huntress
I guess it depends on how fast you can pump them through the machine vs.
how much time it takes to do the second operation on a second machine.

Well, I used to sell and market one of the better multifunction machines
(Wasino), and my opinion is that your job is unlikely to exploit any
advantage from a lathe/mill.


I could see this going pretty fast on a manual machine -- in fact I may
end up doing some of the work on a CAC* machining center. But I don't
really have a good enough mill to do this reasonably fast, and my lathe is
barely up to it.

You just need someone with better machines. I'd still call Dave. He could
give you some further thoughts, having done that kind of thing for a living
for around 40 years.

--
Ed Huntress

Ned Simmons wrote:
On Sat, 30 Aug 2008 14:52:10 -0700, Tim Wescott
wrote:

If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Misumi?
https://fa.misumiusa.com/gwos/catalo...EGORY_I D=006
https://www.misumiusa.com/PDFViewer....e2008&Page=557

They don't do stepped D ends that I could find, and just a stepped shaft
of my dimensions is $8 (qty 1 -- I should have looked for qty 100). So
by the time I get the D put on or the end stepped I'm up to $13 again.

And I expect that the precision and finish of the balance of the shaft
is way more than I need -- not that I know if I'll save anything by not
asking for it.

I'll have another go-round with their system, but if I can't get what I
need from them in one thump, I don't see the value.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Sat, 30 Aug 2008 14:52:10 -0700, Tim Wescott
wrote:

If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those
sorts of volumes, and if I can get this below the $13 that the one
online machine shop I tried wants. I'm also not sure of where I can
compromise on specs to get the price down (the "D" probably has to be +0
- 0.005", the shaft can probably vary +/- 0.005", since it'll be running
in plastic bearings).

Any guidance appreciated.


**** Tim..any of the hobbiests here should be able to knock those out
on a clapped out lathe and a mill in less an an hour..and the 100 lot
in about 1.5 hours if they stopped to take a dump.

$13 each? Thats because the first batch is so small. Order up 1000
and the price could be down about .25 cents each or less

It may be cheaper to order a large batch, than a small one

Depends of course on who supplies the materials.

That job would be a snap on a 2nd ops *turret: machine feeding bar
stock and the flat done on any simple milling machine

Gunner

"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

Gunner Asch wrote:
On Sat, 30 Aug 2008 14:52:10 -0700, Tim Wescott
wrote:

If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch
diameter, mill finish, with one end turned down to 4mm with a 1mm flat
(to make a "D" 4mm diameter and 3mm from flat to round), about 5mm or so
long, with the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those
sorts of volumes, and if I can get this below the $13 that the one
online machine shop I tried wants. I'm also not sure of where I can
compromise on specs to get the price down (the "D" probably has to be +0
- 0.005", the shaft can probably vary +/- 0.005", since it'll be running
in plastic bearings).

Any guidance appreciated.


**** Tim..any of the hobbiests here should be able to knock those out
on a clapped out lathe and a mill in less an an hour..and the 100 lot
in about 1.5 hours if they stopped to take a dump.

$13 each? Thats because the first batch is so small. Order up 1000
and the price could be down about .25 cents each or less

It may be cheaper to order a large batch, than a small one

Depends of course on who supplies the materials.

That job would be a snap on a 2nd ops *turret: machine feeding bar
stock and the flat done on any simple milling machine

Gunner

I think a good part of that $13 (which was the unit price if I ordered
25) was for something machined all over, nice and shiny and bright and
within a gnat's eyelash of the nominal diameter all over.

Which isn't what I need.

I could do the turning part on my Smithy fairly quickly -- particularly
if I don't use welding rod for the production part. But the Smithy
"mill" is a very bad joke; the only way to control the dimension on the
"D" that I know of is cut, nudge, and try.

I am considering paying my kid to do it, particularly if I can figure
out how to set up the milling cut so that he can achieve the accuracy I
need.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

I think a good part of that $13 (which was the unit price if I ordered 25)
was for something machined all over, nice and shiny and bright and within
a gnat's eyelash of the nominal diameter all over.

Looks like that shop charges $300 for setup and cleanup. Then a dollar a
part. If you use cold rolled stock instead of ground you could have saved
$10. bet they didn't even look at that. "The Kid" was an estimator for a
while. for a small new potential customer don't spend but a second doing the
quote. 90% aren't serious.

Karl

Karl Townsend wrote:
I think a good part of that $13 (which was the unit price if I ordered 25)
was for something machined all over, nice and shiny and bright and within
a gnat's eyelash of the nominal diameter all over.

Looks like that shop charges $300 for setup and cleanup. Then a dollar a
part. If you use cold rolled stock instead of ground you could have saved
$10. bet they didn't even look at that. "The Kid" was an estimator for a
while. for a small new potential customer don't spend but a second doing the
quote. 90% aren't serious.

Karl

-- or 90% find out how much it'll cost, and get less serious in a hurry.

I need to make this work, and I think I can get the overall price down
to something I can stand, but it's taking more work than just 'make this
here part be shaped this way'.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Sun, 31 Aug 2008 15:57:28 -0700, Tim Wescott
wrote:

Karl Townsend wrote:
I think a good part of that $13 (which was the unit price if I ordered 25)
was for something machined all over, nice and shiny and bright and within
a gnat's eyelash of the nominal diameter all over.

Looks like that shop charges $300 for setup and cleanup. Then a dollar a
part. If you use cold rolled stock instead of ground you could have saved
$10. bet they didn't even look at that. "The Kid" was an estimator for a
while. for a small new potential customer don't spend but a second doing the
quote. 90% aren't serious.

Karl

-- or 90% find out how much it'll cost, and get less serious in a hurry.

I need to make this work, and I think I can

get the overall price down
to something I can stand, but it's taking more work than just 'make this
here part be shaped this way'

If you're not having any luck getting bids for you to shop, you might
try saying what you would be willing to pay per lot for 10, 100 and
200 pcs. Makes it easy for others to simply respond or not. That
might include folks in this n.g.

You don't mention schedule. Could this be a fill or "spare time" job?
You don't mention material.

I would think you could make these parts on your Smithy yourself in
less time than you'll spend screwing around with negotiations,
particularly if you allow use of more expensive but easy-to-machine
materials like 12L14 steel, brass or aluminum.

Don't forget that another person who makes these for you has to
procure the material, ship you the finished parts, and spend whatever
time it takes to bill and collect.

I agree with Gunner: even with non-CNC machines and making the flat
as a second op, I rather doubt that it'd take me 2 hours to make 100
of these parts as you've described them -- but I'm not at all sure
that a price you'd regard as reasonable would match my threshold for
doing your project instead of mine -- e.g. going fishing or something.
If you posted a print, spec and acceptable price somewhere you might
get more interest. It would also save you time in the long run. Say
in your spec that if parts meet spec they will be accepted even if
they aren't quite what you had in mind. Making the spec and print
describe what you need and want is your responsibility.

Don Foreman wrote:
On Sun, 31 Aug 2008 15:57:28 -0700, Tim Wescott
wrote:

Karl Townsend wrote:
I think a good part of that $13 (which was the unit price if I ordered 25)
was for something machined all over, nice and shiny and bright and within
a gnat's eyelash of the nominal diameter all over.
Looks like that shop charges $300 for setup and cleanup. Then a dollar a
part. If you use cold rolled stock instead of ground you could have saved
$10. bet they didn't even look at that. "The Kid" was an estimator for a
while. for a small new potential customer don't spend but a second doing the
quote. 90% aren't serious.

Karl

-- or 90% find out how much it'll cost, and get less serious in a hurry.

I need to make this work, and I think I can

get the overall price down
to something I can stand, but it's taking more work than just 'make this
here part be shaped this way'

If you're not having any luck getting bids for you to shop, you might
try saying what you would be willing to pay per lot for 10, 100 and
200 pcs. Makes it easy for others to simply respond or not. That
might include folks in this n.g.

That's partially because I'm still estimating the price of the whole
assembly, and partially because I've a paranoia about folks just bidding
up to my minimum.

$0/ea would be nice, but is clearly unreachable. $200/100 would be very
nice, but that would barely buy material. $1000/100 is OUCH, and I
could live with $500/100, but I might keep looking.

Oh -- after all that "per 100" stuff, the initial order would be for
more like 10.

You don't mention schedule. Could this be a fill or "spare time" job?

At this point, yes. I'm in early prototyping now, and I'm doing this as
a fill job myself. It may heat up enough that at some point I'd have to
get firm time commitments, but I think I could keep them long.

You don't mention material.

Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).

I would think you could make these parts on your Smithy yourself in
less time than you'll spend screwing around with negotiations,
particularly if you allow use of more expensive but easy-to-machine
materials like 12L14 steel, brass or aluminum.

Hmm. Perish the thought. That may do for the first 10, but I've got a
bunch more stuff to do than just the shafts.

Hmm again.

Don't forget that another person who makes these for you has to
procure the material, ship you the finished parts, and spend whatever
time it takes to bill and collect.

True.

I agree with Gunner: even with non-CNC machines and making the flat
as a second op, I rather doubt that it'd take me 2 hours to make 100
of these parts as you've described them -- but I'm not at all sure
that a price you'd regard as reasonable would match my threshold for
doing your project instead of mine -- e.g. going fishing or something.
If you posted a print, spec and acceptable price somewhere you might
get more interest. It would also save you time in the long run. Say
in your spec that if parts meet spec they will be accepted even if
they aren't quite what you had in mind. Making the spec and print
describe what you need and want is your responsibility.

So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?

A big part of my problem is that while I've gotten a bit of drafting in
high school, and I've worked around mechanical engineers for years, it
was all for very high-falutin stuff. So everything gets engineered down
to the gnat's eyelash, and "expensive" is a $10 part that keeps a
$500,000 system from working, not a $50 part that works perfectly all
the time.

So any instincts that I have are all skewed the wrong way.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:



You don't mention material.

Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).

OK, so can't rust implies steel is OK if plated, otherwise brass, ally
or SS. If making bazillions of them they'd be plated steel because
the plating cost is negligable in large batches.

I don't understand the bit of triplestep but ally isn't that much
cheaper than brass so if you have reservations with ally I'd just
exclude it. 3/16" brass is about a buck a foot or about $0.45 per
gizmo. Some might find a few cents more for material to be
advantageous in terms of processing time. BTW, brass runs real nice in
plastic bearings, particularly delrin.

Brass won't rust but it will tarnish after a while. If that'd be
objectionable you need to say so. Then 303 would probably be the
best choice. 303 is very easy to machine in a rigid lathe but not as
easy as brass in a less-rigid lathe.


So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?

Just dimension the length with tolerance suitable for your
application. You don't have to say "cheap"; nobody ever wants "costs
more than would be necessary". With your specs I'm not sure if I'd
part off blanks in the lathe or just shear them.

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".

A big part of my problem is that while I've gotten a bit of drafting in
high school, and I've worked around mechanical engineers for years, it
was all for very high-falutin stuff. So everything gets engineered down
to the gnat's eyelash, and "expensive" is a $10 part that keeps a
$500,000 system from working, not a $50 part that works perfectly all
the time.

So any instincts that I have are all skewed the wrong way.

This sounds more like a "consumer" deal. None of them will need to
work flawlessly for thousands of hours, right?

Don Foreman wrote:
On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:


You don't mention material.
Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).

OK, so can't rust implies steel is OK if plated, otherwise brass, ally
or SS. If making bazillions of them they'd be plated steel because
the plating cost is negligable in large batches.

I don't understand the bit of triplestep but ally isn't that much
cheaper than brass so if you have reservations with ally I'd just
exclude it. 3/16" brass is about a buck a foot or about $0.45 per
gizmo. Some might find a few cents more for material to be
advantageous in terms of processing time. BTW, brass runs real nice in
plastic bearings, particularly delrin.

Brass won't rust but it will tarnish after a while. If that'd be
objectionable you need to say so. Then 303 would probably be the
best choice. 303 is very easy to machine in a rigid lathe but not as
easy as brass in a less-rigid lathe.

So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?

Just dimension the length with tolerance suitable for your
application. You don't have to say "cheap"; nobody ever wants "costs
more than would be necessary". With your specs I'm not sure if I'd
part off blanks in the lathe or just shear them.

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".
A big part of my problem is that while I've gotten a bit of drafting in
high school, and I've worked around mechanical engineers for years, it
was all for very high-falutin stuff. So everything gets engineered down
to the gnat's eyelash, and "expensive" is a $10 part that keeps a
$500,000 system from working, not a $50 part that works perfectly all
the time.

So any instincts that I have are all skewed the wrong way.

This sounds more like a "consumer" deal. None of them will need to
work flawlessly for thousands of hours, right?

You're making me think this through, Don, which is one of the things I
was hoping for with my original post. I'm not sure what motivated me to
reject brass over stainless, but I see that 360 is only a hair more
expensive than 303 stainless, and it'll be way way easier to machine.

Maybe I'll get one stick of each from McMaster for prototyping, and see
what I think of it for myself.

One of my great frustrations on this project is that the driver for this
shaft design is a great little potentiometer with poorly defined
specifications. It costs about 1/3 as much as anything else that would
be remotely feasible, it has low friction, it slaps onto a surface-mount
board with all the same processes as the other parts, and has other good
features.

But the data sheet (at least the English-language one) doesn't give any
specs for how close to center the thing has to be run -- and I have to
account for shaft runout, bearing slop, _and_ board misalignment in my
error budget. At this point I'm guessing that .005 would be on the edge
of what's acceptable; I'll have to go over my measurements of the part
to make sure.

An alternative that I had rejected, but am now thinking may make sense,
would be to use a 1/4" shaft that's stepped down to 3/16 then again to
4mm. If this is done all in one step it would make it easy to get
really good concentricity (I'm not sure how good, but .0005 ought to be
quite achievable, yes?).

I wonder how much extra that would cost... I could still go 1/4" on the
off-end to allow it to just be cut in a shear. The cost would be two
sizes of bearings, but I don't see that as a big deal if it makes the
shaft enough less of a deal.

(here's the bearing I'm planning on using:
http://www.igus.com/igubal/igall2.asp?p=Clip).

If I could categorize the finished assembly it'd be "pro consumer". I'm
going to be teaching some control systems seminars, to take embedded
software engineers and spin them up on applying control systems theory
in software. In order to do this I'm making a gizmo with a simple & fun
mechanism, with a board that controls it. The intent is to get the
price to a point where I can send one home to each attendee (it's not
going to be a cheap seminar).

So it needs to work well for occasional use by one person for a year or
so, at which point it'll gather so much dust it won't be recognizable.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:

I agree with Gunner: even with non-CNC machines and making the flat
as a second op, I rather doubt that it'd take me 2 hours to make 100
of these parts as you've described them -- but I'm not at all sure
that a price you'd regard as reasonable would match my threshold for
doing your project instead of mine -- e.g. going fishing or something.
If you posted a print, spec and acceptable price somewhere you might
get more interest. It would also save you time in the long run. Say
in your spec that if parts meet spec they will be accepted even if
they aren't quite what you had in mind. Making the spec and print
describe what you need and want is your responsibility.

So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?


Shrug...based on my experience, you find a small job shop..maybe a
swiss machine house..and bring in your notes and your print...and you
talk, face to face with the head honco. You put arrows with numbers on
the places you are concerned about..and you tell the guy you want the
thiing made as cheaply as possible, and the numbered places can be
anyway he thinks will be cheapest and still work...etc etc

Unless you are specing the materials..you tell him to make it out of
whatever leftovers he has on hand that will do the job.
A lot of small shops have uncertified stuff that is collecting dust on
racks. Is it steel? Yep. Is it stainless? Yup What kind? No idea.
Can I get it really cheap? Yep.

Shrug

Wont hurt to bring in some donuts either. Tell the dude what you are
trying to do,

As I said before..sometimes you can get 500 parts cheaper than you can
100..or for the same price.

If you were in So. Cal..I likely could get it "brother in lawed" for
you pretty cheap.

Or I could get you a second ops lath really cheap. Humm...Ive got
this Kitikura turret lathe..cute little *******....uses 4C
collets....G

Gunner

"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On Mon, 01 Sep 2008 11:02:00 -0500, Don Foreman
wrote:

On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:



You don't mention material.

Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).

OK, so can't rust implies steel is OK if plated, otherwise brass, ally
or SS. If making bazillions of them they'd be plated steel because
the plating cost is negligable in large batches.

I don't understand the bit of triplestep but ally isn't that much
cheaper than brass so if you have reservations with ally I'd just
exclude it. 3/16" brass is about a buck a foot or about $0.45 per
gizmo. Some might find a few cents more for material to be
advantageous in terms of processing time. BTW, brass runs real nice in
plastic bearings, particularly delrin.

stainless steel is cheaper than brass, particularly in the quantiies
screw machine shops buy it in. You dont care if its 303, 304,
316...just that it doesnt rust.

See my previous post about uncertified bars collecting dust....

Gunner

"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On Mon, 01 Sep 2008 11:02:00 -0500, Don Foreman
wrote:

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".



Its gonna be collet work. No shop would put it in a chuck


"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On Mon, 01 Sep 2008 12:01:49 -0700, Gunner Asch
wrote:

On Mon, 01 Sep 2008 11:02:00 -0500, Don Foreman
wrote:

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".



Its gonna be collet work. No shop would put it in a chuck

Would a shop (as you define it) be interested in a job like this for
low hundreds of $?

On Mon, 01 Sep 2008 10:28:45 -0700, Tim Wescott
wrote:

Don Foreman wrote:
On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:


You don't mention material.
Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).

OK, so can't rust implies steel is OK if plated, otherwise brass, ally
or SS. If making bazillions of them they'd be plated steel because
the plating cost is negligable in large batches.

I don't understand the bit of triplestep but ally isn't that much
cheaper than brass so if you have reservations with ally I'd just
exclude it. 3/16" brass is about a buck a foot or about $0.45 per
gizmo. Some might find a few cents more for material to be
advantageous in terms of processing time. BTW, brass runs real nice in
plastic bearings, particularly delrin.

Brass won't rust but it will tarnish after a while. If that'd be
objectionable you need to say so. Then 303 would probably be the
best choice. 303 is very easy to machine in a rigid lathe but not as
easy as brass in a less-rigid lathe.

So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?

Just dimension the length with tolerance suitable for your
application. You don't have to say "cheap"; nobody ever wants "costs
more than would be necessary". With your specs I'm not sure if I'd
part off blanks in the lathe or just shear them.

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".
A big part of my problem is that while I've gotten a bit of drafting in
high school, and I've worked around mechanical engineers for years, it
was all for very high-falutin stuff. So everything gets engineered down
to the gnat's eyelash, and "expensive" is a $10 part that keeps a
$500,000 system from working, not a $50 part that works perfectly all
the time.

So any instincts that I have are all skewed the wrong way.

This sounds more like a "consumer" deal. None of them will need to
work flawlessly for thousands of hours, right?

You're making me think this through, Don, which is one of the things I
was hoping for with my original post. I'm not sure what motivated me to
reject brass over stainless, but I see that 360 is only a hair more
expensive than 303 stainless, and it'll be way way easier to machine.

Maybe I'll get one stick of each from McMaster for prototyping, and see
what I think of it for myself.

One of my great frustrations on this project is that the driver for this
shaft design is a great little potentiometer with poorly defined
specifications. It costs about 1/3 as much as anything else that would
be remotely feasible, it has low friction, it slaps onto a surface-mount
board with all the same processes as the other parts, and has other good
features.

But the data sheet (at least the English-language one) doesn't give any
specs for how close to center the thing has to be run -- and I have to
account for shaft runout, bearing slop, _and_ board misalignment in my
error budget. At this point I'm guessing that .005 would be on the edge
of what's acceptable; I'll have to go over my measurements of the part
to make sure.

An alternative that I had rejected, but am now thinking may make sense,
would be to use a 1/4" shaft that's stepped down to 3/16 then again to
4mm. If this is done all in one step it would make it easy to get
really good concentricity (I'm not sure how good, but .0005 ought to be
quite achievable, yes?).

I wonder how much extra that would cost... I could still go 1/4" on the
off-end to allow it to just be cut in a shear. The cost would be two
sizes of bearings, but I don't see that as a big deal if it makes the
shaft enough less of a deal.

(here's the bearing I'm planning on using:
http://www.igus.com/igubal/igall2.asp?p=Clip).

If I could categorize the finished assembly it'd be "pro consumer". I'm
going to be teaching some control systems seminars, to take embedded
software engineers and spin them up on applying control systems theory
in software. In order to do this I'm making a gizmo with a simple & fun
mechanism, with a board that controls it. The intent is to get the
price to a point where I can send one home to each attendee (it's not
going to be a cheap seminar).

So it needs to work well for occasional use by one person for a year or
so, at which point it'll gather so much dust it won't be recognizable.

Sounds like the pot has a D-shaped hole rather than a shaft. Then, it
sounds like you want to have a shaft that goes thru bearings engage
this pot that is affixed to a board affixed to ??? -- and have
everything line up so nothing binds -- and I'm guessing that you want
rotational backlash betwen shaft and pot to be somewhere between
minimal and none.

You're only building 200 of these things, so automated assembly isn't
an issue.

I'd say float the pot on the shaft, let it self-center. Maybe it's on
a small daughterboard with a little connector. Restrain the pot body
from rotation with a bit of silicone and connect electrically via
small wires or ribbon cable.

If this sounds slightly vague, think about what your requirements and
ambitions might sound like to a shop owner/operator who can't afford
to spend more than a few minutes of non-production time on a few
hundred dollar project.

Think about what you charge per minute of your time!

On Mon, 01 Sep 2008 20:26:19 -0500, Don Foreman
wrote:

On Mon, 01 Sep 2008 12:01:49 -0700, Gunner Asch
wrote:

On Mon, 01 Sep 2008 11:02:00 -0500, Don Foreman
wrote:

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".



Its gonna be collet work. No shop would put it in a chuck

Would a shop (as you define it) be interested in a job like this for
low hundreds of $?


Of course. Money is money. Big or small..they is in the biz

Gunner

"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

In article ,
Tim Wescott wrote:

[big snip]

One of my great frustrations on this project is that the driver for this
shaft design is a great little potentiometer with poorly defined
specifications. It costs about 1/3 as much as anything else that would
be remotely feasible, it has low friction, it slaps onto a surface-mount
board with all the same processes as the other parts, and has other good
features.

But the data sheet (at least the English-language one) doesn't give any
specs for how close to center the thing has to be run -- and I have to
account for shaft runout, bearing slop, _and_ board misalignment in my
error budget. At this point I'm guessing that .005 would be on the edge
of what's acceptable; I'll have to go over my measurements of the part
to make sure.

The 0.005" would be for a rigid setup. Angular misalignment is also
tolerable.


An alternative that I had rejected, but am now thinking may make sense,
would be to use a 1/4" shaft that's stepped down to 3/16 then again to
4mm. If this is done all in one step it would make it easy to get
really good concentricity (I'm not sure how good, but .0005 ought to be
quite achievable, yes?).

I wonder how much extra that would cost... I could still go 1/4" on the
off-end to allow it to just be cut in a shear. The cost would be two
sizes of bearings, but I don't see that as a big deal if it makes the
shaft enough less of a deal.

I would make the shaft flexible near the pot, so a little misalignment
won't matter. One approach would be a D-shaped brass or mild steel plug
soft soldered to one end of a bit of music wire, the other end of which
is soft soldered to the real shaft. The music wire bit would not need
to be that long.

A classic alternative is a rigid shaft with the D machined in one end,
but allowed to move in angle, held by a single panel bearing and clamp
collar.

Joe Gwinn



(here's the bearing I'm planning on using:
http://www.igus.com/igubal/igall2.asp?p=Clip).

If I could categorize the finished assembly it'd be "pro consumer". I'm
going to be teaching some control systems seminars, to take embedded
software engineers and spin them up on applying control systems theory
in software. In order to do this I'm making a gizmo with a simple & fun
mechanism, with a board that controls it. The intent is to get the
price to a point where I can send one home to each attendee (it's not
going to be a cheap seminar).

So it needs to work well for occasional use by one person for a year or
so, at which point it'll gather so much dust it won't be recognizable.

Don Foreman wrote:
On Mon, 01 Sep 2008 10:28:45 -0700, Tim Wescott
wrote:

Don Foreman wrote:
On Mon, 01 Sep 2008 07:54:47 -0700, Tim Wescott
wrote:


You don't mention material.
Thank you -- this is why I post these questions to the group, because
you know all the things I should be saying.

It's gotta not rust in a living room environment, and stainless (at
least from McMaster) is cheaper than brass. 6061 Aluminum may work at a
larger diameter than 3/16, but then I'd have to triple-step the shafts
or have huge bearings (which I don't want).
OK, so can't rust implies steel is OK if plated, otherwise brass, ally
or SS. If making bazillions of them they'd be plated steel because
the plating cost is negligable in large batches.

I don't understand the bit of triplestep but ally isn't that much
cheaper than brass so if you have reservations with ally I'd just
exclude it. 3/16" brass is about a buck a foot or about $0.45 per
gizmo. Some might find a few cents more for material to be
advantageous in terms of processing time. BTW, brass runs real nice in
plastic bearings, particularly delrin.

Brass won't rust but it will tarnish after a while. If that'd be
objectionable you need to say so. Then 303 would probably be the
best choice. 303 is very easy to machine in a rigid lathe but not as
easy as brass in a less-rigid lathe.

So what's drafting-ease for "make the shoulder any damn thing you want
as long as it's cheap"? Ditto for "cut the off-end of the shaft any
damn way you want as long as it's cheap"?
Just dimension the length with tolerance suitable for your
application. You don't have to say "cheap"; nobody ever wants "costs
more than would be necessary". With your specs I'm not sure if I'd
part off blanks in the lathe or just shear them.

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".
A big part of my problem is that while I've gotten a bit of drafting in
high school, and I've worked around mechanical engineers for years, it
was all for very high-falutin stuff. So everything gets engineered down
to the gnat's eyelash, and "expensive" is a $10 part that keeps a
$500,000 system from working, not a $50 part that works perfectly all
the time.

So any instincts that I have are all skewed the wrong way.
This sounds more like a "consumer" deal. None of them will need to
work flawlessly for thousands of hours, right?
You're making me think this through, Don, which is one of the things I
was hoping for with my original post. I'm not sure what motivated me to
reject brass over stainless, but I see that 360 is only a hair more
expensive than 303 stainless, and it'll be way way easier to machine.

Maybe I'll get one stick of each from McMaster for prototyping, and see
what I think of it for myself.

One of my great frustrations on this project is that the driver for this
shaft design is a great little potentiometer with poorly defined
specifications. It costs about 1/3 as much as anything else that would
be remotely feasible, it has low friction, it slaps onto a surface-mount
board with all the same processes as the other parts, and has other good
features.

But the data sheet (at least the English-language one) doesn't give any
specs for how close to center the thing has to be run -- and I have to
account for shaft runout, bearing slop, _and_ board misalignment in my
error budget. At this point I'm guessing that .005 would be on the edge
of what's acceptable; I'll have to go over my measurements of the part
to make sure.

An alternative that I had rejected, but am now thinking may make sense,
would be to use a 1/4" shaft that's stepped down to 3/16 then again to
4mm. If this is done all in one step it would make it easy to get
really good concentricity (I'm not sure how good, but .0005 ought to be
quite achievable, yes?).

I wonder how much extra that would cost... I could still go 1/4" on the
off-end to allow it to just be cut in a shear. The cost would be two
sizes of bearings, but I don't see that as a big deal if it makes the
shaft enough less of a deal.

(here's the bearing I'm planning on using:
http://www.igus.com/igubal/igall2.asp?p=Clip).

If I could categorize the finished assembly it'd be "pro consumer". I'm
going to be teaching some control systems seminars, to take embedded
software engineers and spin them up on applying control systems theory
in software. In order to do this I'm making a gizmo with a simple & fun
mechanism, with a board that controls it. The intent is to get the
price to a point where I can send one home to each attendee (it's not
going to be a cheap seminar).

So it needs to work well for occasional use by one person for a year or
so, at which point it'll gather so much dust it won't be recognizable.

Sounds like the pot has a D-shaped hole rather than a shaft. Then, it
sounds like you want to have a shaft that goes thru bearings engage
this pot that is affixed to a board affixed to ??? -- and have
everything line up so nothing binds -- and I'm guessing that you want
rotational backlash betwen shaft and pot to be somewhere between
minimal and none.

You're only building 200 of these things, so automated assembly isn't
an issue.

I'd say float the pot on the shaft, let it self-center. Maybe it's on
a small daughterboard with a little connector. Restrain the pot body
from rotation with a bit of silicone and connect electrically via
small wires or ribbon cable.

If this sounds slightly vague, think about what your requirements and
ambitions might sound like to a shop owner/operator who can't afford
to spend more than a few minutes of non-production time on a few
hundred dollar project.

Think about what you charge per minute of your time!

The pot does indeed have a D-shaped hole. It's a surface-mount part
that mounts hard to the board, so once it's down on the board it's
married. Boards are expensive as piece parts, so I really don't want to
go to a second board just for a flex mounting -- I think Joe Gwinn's
flex shaft suggestion has merit, if I need to go there.

I the mean time I think I'll hard mount.

I also think I'll do the first dozen or so here on my Smithy, to get the
design right. It'll give me an excuse to get a set of collets, if
nothing else.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Tue, 02 Sep 2008 07:33:18 -0700, Tim Wescott
wrote:

Don Foreman wrote:


The pot does indeed have a D-shaped hole. It's a surface-mount part
that mounts hard to the board, so once it's down on the board it's
married. Boards are expensive as piece parts, so I really don't want to
go to a second board just for a flex mounting

Less than 1 square inch at 50 cents per square inch ....

-- I think Joe Gwinn's
flex shaft suggestion has merit, if I need to go there.

That approach occurred to me also. Easier with a pot that has a
shaft, but might be workable here. The flex member could be a small
spring or even a bit of polymer tubing.

On Tue, 02 Sep 2008 00:21:04 -0700, Gunner Asch
wrote:

On Mon, 01 Sep 2008 20:26:19 -0500, Don Foreman
wrote:

On Mon, 01 Sep 2008 12:01:49 -0700, Gunner Asch
wrote:

On Mon, 01 Sep 2008 11:02:00 -0500, Don Foreman
wrote:

BTW, if you have a concentricity requirement for the shaft body and
machined part, you need to specify it. A shiny spiffy shop would have
machines that hold a couple of tenths but guys that might want such a
job could well have chucks that are out .005".



Its gonna be collet work. No shop would put it in a chuck

Would a shop (as you define it) be interested in a job like this for
low hundreds of $?


Of course. Money is money. Big or small..they is in the biz

Gunner

I'll bet it would take considerably less time to just make the parts
than it would to make a spec and print and visit shops until one is
found that wants to mess with it.

This is particularly so when one might want to make a couple and see
how they work and possibly revise the design before making 100 or 200.
It's also particularly so when 100 to 200 is very likely all that will
ever be wanted.

What's really needed here is not a machinist but a modelmaker. The
difference: with a good modelmaker, you sit down and describe what
you are trying to accomplish with sketches, conversation, handwaving,
etc. He will think about it for a while and then make something that
does what the engineer wanted. The engineer then makes a drawing of
it and takes credit for inventing the damned thing.

Most model shops do *NOT* allow the engineers to touch their machinery
or tools -- for good reason!

The engineer who has a shop (or is allowed in the model shop after
demonstrating proficiency) can be his own modelmaker to some extent,
though accquiring the skill level of a really good modelmaker would
take decades.

On Tue, 02 Sep 2008 10:25:42 -0500, Don Foreman
wrote:

On Tue, 02 Sep 2008 07:33:18 -0700, Tim Wescott
wrote:

Don Foreman wrote:


The pot does indeed have a D-shaped hole. It's a surface-mount part
that mounts hard to the board, so once it's down on the board it's
married. Boards are expensive as piece parts, so I really don't want to
go to a second board just for a flex mounting

Less than 1 square inch at 50 cents per square inch ....

-- I think Joe Gwinn's
flex shaft suggestion has merit, if I need to go there.

That approach occurred to me also. Easier with a pot that has a
shaft, but might be workable here. The flex member could be a small
spring or even a bit of polymer tubing.

Tubing is good and lasts for a good long time if propery picked. Bit
of Superglue if necessary.


"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On Tue, 02 Sep 2008 10:43:46 -0500, Don Foreman
wrote:


Of course. Money is money. Big or small..they is in the biz

Gunner

I'll bet it would take considerably less time to just make the parts
than it would to make a spec and print and visit shops until one is
found that wants to mess with it.


Ive seen tons of parts machined from descriptions done on cardboard
box ends, napkins and scrap paper.

Not every body needs a print with callouts to 4 decimals. Particuarly
with such a simple part.

Shrug...but hey..what do I know? Its not like Im in the biz or
anything....

G

Gunner
Coyote Engineering
Machine tool repair, setup
OmniTurn CNC specialist
Hardinge Manuals
Infrastructure repair and updates
Electrical (non Lic.) up to 480
Controls and motors
Serving Central and Southern California, and Arizona


"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

With all of the details out, there must be lots of different
materials/parts/ways to allow you to turn a pot, after all.. it's been done
millions of times by now.

Various other approaches

Source shaft material with a continuous flat
Select a knob that fits above shafting
Select a pot with a different center piece
Shaft made from tubing

Consider reinforced plastic shafts or,
Source double-ended tweaking screwdrivers cut in two, to make 2 shafts
Select knobs that fit smaller/readily-available shaft materials

The part is too complicated to make in large numbers or to have custom-made,
just to turn a pot, IMO.

Chucking individual lengths to reduce the diameter is going to be time
consuming, whether you use a 3-jaw or collets. BTW, common morse collets
don't allow feedthru.

If I needed a steel shaft with the specs you listed, I'd go make a batch of
them as far as the reduced diameter, then try several different ways to add
the flat.

Feeding a length to be turned (3-jaw chuck), then rechucking for a cutoff is
also time consuming, so I'd be tempted to hacksaw the length (maybe 3
strokes) by holding the free end, after reducing the diameter and
re-chucking for turning the next diameter reduction cut. Sawing generally
demands deburring and/or other finishing.

For milling the flat, unless there was a fixture available to hold numerous
shafts parallel to each other (closely together), they would probably need
to be secured in a vise individually, which is almost as much effort as
making the cutting pass for the flat.

WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Tim Wescott" wrote in message
...
If I wanted to buy a bunch of 4.5" long shafts, 3/16 or 1/4 inch diameter,
mill finish, with one end turned down to 4mm with a 1mm flat (to make a
"D" 4mm diameter and 3mm from flat to round), about 5mm or so long, with
the shoulder profile being quite unimportant.

Prototype runs of 10 or so, production orders of one or two hundred.

My understanding is that this is a job for an NC lathe, and that most if
not all of them would have an attachment for milling the flat, so the
operation would be feed, turn down, cut the flat, cut off, repeat.

What I'm not so sure of is where to find someone interested in those sorts
of volumes, and if I can get this below the $13 that the one online
machine shop I tried wants. I'm also not sure of where I can compromise
on specs to get the price down (the "D" probably has to be +0 - 0.005",
the shaft can probably vary +/- 0.005", since it'll be running in plastic
bearings).

Any guidance appreciated.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" gives you just what it says.
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