On 21 Dec 2005 07:12:10 -0800, "Guy Fawkes"
wrote:

OK, first off my background, I'm a time served (marine) engineer, and
can muddle my way through most simple tasks on most basic machine shop
tools, and I'm planning on buying a small home CNC setup such as the
sherline ultimate mill / lathe package in the spring of 2006.

I'm also pretty computer savvy, and I know the theory behind CNC.

If you have 100 one off jobs like taking the corroded ends of heat
exchangers and dressing them up by making new bushes old tools and old
style machinists win every time, whereas if you want to make 10,000
identical parts such as a 5/16 threaded bolt with a 1/8th stub
protruding for 1/2 an inch with a 60 degree taper on the last 1/4 then
CNC is the daddy.

I guess there is an inherent assumption here that a skilled traditional
machinist is going to be more knowledgeable, flexible and resourceful
than a CNC jockey..... (?)

My question is this.

What, if any tasks are suited to CNC to such an extent that they would
be damn near impossible of excessively difficult (eg expensive) with a
traditional machinist?

Are we talking only complex things such as the "rotor"
http://www.mono-pumps.com/mono/home.nsf/p/D974BC2AC71AF6A280256EFC0060248F/$file/Parts.jpg
in a mono progressive cavity pump?

Or are there other areas where CNC beats the "old way"?

For example, it appears to me that CNC will require much more effort
prior to starting machining in setting up the blank work piece, both
for positioning and alignment, and also if billets then making sure
they are all identical prior to machining?

If there is a bias to this question it is towards "hobby" uses such as
a sherline rather than a production commercial shop, but I'd still be
interested in that aspect generally.

TIA

Crossposted to rec.crafts.metalworking
--
Cliff

I have VERY limited CNC experience. Recently I have been using a
Bridgeport EZ-Trak which is a 2 axis sort-of CNC machine.
To answer your question about the "tasks suited to CNC" and "damn
near impossible": Large holes and contoured shapes. I guess it
might be possible to mill a 3" hole in the center of a 1" thick plate by
using the dials on a manual machine, but I wouldn't want to try it.
whereas with the CNC machine, all you have to do is to write a 4 line
program which invokes a canned program to make that hole in any one of 3
different ways.

Soon as I save up $10K I'm gonna get me one of them EZ-Traks.

Pete Stanaitis
---------------------


Cliff wrote:
On 21 Dec 2005 07:12:10 -0800, "Guy Fawkes"
wrote:


OK, first off my background, I'm a time served (marine) engineer, and
can muddle my way through most simple tasks on most basic machine shop
tools, and I'm planning on buying a small home CNC setup such as the
sherline ultimate mill / lathe package in the spring of 2006.

I'm also pretty computer savvy, and I know the theory behind CNC.

If you have 100 one off jobs like taking the corroded ends of heat
exchangers and dressing them up by making new bushes old tools and old
style machinists win every time, whereas if you want to make 10,000
identical parts such as a 5/16 threaded bolt with a 1/8th stub
protruding for 1/2 an inch with a 60 degree taper on the last 1/4 then
CNC is the daddy.

I guess there is an inherent assumption here that a skilled traditional
machinist is going to be more knowledgeable, flexible and resourceful
than a CNC jockey..... (?)

My question is this.

What, if any tasks are suited to CNC to such an extent that they would
be damn near impossible of excessively difficult (eg expensive) with a
traditional machinist?

Are we talking only complex things such as the "rotor"
http://www.mono-pumps.com/mono/home.nsf/p/D974BC2AC71AF6A280256EFC0060248F/$file/Parts.jpg
in a mono progressive cavity pump?

Or are there other areas where CNC beats the "old way"?

For example, it appears to me that CNC will require much more effort
prior to starting machining in setting up the blank work piece, both
for positioning and alignment, and also if billets then making sure
they are all identical prior to machining?

If there is a bias to this question it is towards "hobby" uses such as
a sherline rather than a production commercial shop, but I'd still be
interested in that aspect generally.

TIA


Crossposted to rec.crafts.metalworking

Cliff wrote:
On 21 Dec 2005 07:12:10 -0800, "Guy Fawkes"
wrote:


OK, first off my background, I'm a time served (marine) engineer, and
can muddle my way through most simple tasks on most basic machine shop
tools, and I'm planning on buying a small home CNC setup such as the
sherline ultimate mill / lathe package in the spring of 2006.

I'm also pretty computer savvy, and I know the theory behind CNC.

If you have 100 one off jobs like taking the corroded ends of heat
exchangers and dressing them up by making new bushes old tools and old
style machinists win every time, whereas if you want to make 10,000
identical parts such as a 5/16 threaded bolt with a 1/8th stub
protruding for 1/2 an inch with a 60 degree taper on the last 1/4 then
CNC is the daddy.

I guess there is an inherent assumption here that a skilled traditional
machinist is going to be more knowledgeable, flexible and resourceful
than a CNC jockey..... (?)

My question is this.

What, if any tasks are suited to CNC to such an extent that they would
be damn near impossible of excessively difficult (eg expensive) with a
traditional machinist?
There are tons of things that can be done easily by CNC that will be
VERY time-consuming to setup on manual machines. Most obvious is
anything that requires a rotary table on a manual mill. You have
to do all sorts of indicating to put the right spot of the part on the
center of the RT. If you need a rectangular pocket with rounded corners
you need to mill the rectangle conventionally, then re-set the part FOUR
times on the RT. With the CNC, it is 4 linear paths and 4 arc paths,
and you are done. Bang! I'd like to see a manual machinist beat me
with CNC. (You can set up a boring head to the right radius to do these
rounded corners, so maybe that is not the best example.)

Check out the 2nd and 4th pictures here
http://jelinux.pico-systems.com/worklite.html
to see something that was trivial with CNC. The inside corners are angled.
The entire pocket was cut in one continuous trajectory with CNC.
Try an O-ring groove to seal a rectangular cover plate. Again, trivial
with CNC, even for a one-off.

Here's another - check the exterior shape of the bracket that holds this
auxilliary spindle http://jelinux.pico-systems.com/wwspndl.html
It is not real easy to see the whole shape, but it is all arcs and
funny angles. I have a drawing on Tim Goldstein's CAD CAM pages, but
I can't get it to come up right now.

Jon

Jon Elson wrote:
Cliff wrote:
On 21 Dec 2005 07:12:10 -0800, "Guy Fawkes"
wrote:


OK, first off my background, I'm a time served (marine) engineer, and
can muddle my way through most simple tasks on most basic machine shop
tools, and I'm planning on buying a small home CNC setup such as the
sherline ultimate mill / lathe package in the spring of 2006.

I'm also pretty computer savvy, and I know the theory behind CNC.

If you have 100 one off jobs like taking the corroded ends of heat
exchangers and dressing them up by making new bushes old tools and old
style machinists win every time, whereas if you want to make 10,000
identical parts such as a 5/16 threaded bolt with a 1/8th stub
protruding for 1/2 an inch with a 60 degree taper on the last 1/4 then
CNC is the daddy.

I guess there is an inherent assumption here that a skilled traditional
machinist is going to be more knowledgeable, flexible and resourceful
than a CNC jockey..... (?)

My question is this.

What, if any tasks are suited to CNC to such an extent that they would
be damn near impossible of excessively difficult (eg expensive) with a
traditional machinist?
There are tons of things that can be done easily by CNC that will be
VERY time-consuming to setup on manual machines. Most obvious is
anything that requires a rotary table on a manual mill. You have
to do all sorts of indicating to put the right spot of the part on the
center of the RT. If you need a rectangular pocket with rounded corners
you need to mill the rectangle conventionally, then re-set the part FOUR
times on the RT. With the CNC, it is 4 linear paths and 4 arc paths,
and you are done. Bang! I'd like to see a manual machinist beat me
with CNC. (You can set up a boring head to the right radius to do these
rounded corners, so maybe that is not the best example.)

Check out the 2nd and 4th pictures here
http://jelinux.pico-systems.com/worklite.html
to see something that was trivial with CNC. The inside corners are angled.
The entire pocket was cut in one continuous trajectory with CNC.
Try an O-ring groove to seal a rectangular cover plate. Again, trivial
with CNC, even for a one-off.

Here's another - check the exterior shape of the bracket that holds this
auxilliary spindle http://jelinux.pico-systems.com/wwspndl.html
It is not real easy to see the whole shape, but it is all arcs and
funny angles. I have a drawing on Tim Goldstein's CAD CAM pages, but
I can't get it to come up right now.

Jon



"If you need a rectangular pocket with rounded corners you need to mill
the rectangle conventionally, then re-set the part FOUR times on the
RT."

Perhaps to be fair we should mention using a Volstro milling head
attachment. Using one in the past has saved me a lot of time. The
Volstro head is not very rigid though... then again neither are most
knee mills.... but knee mills still have a place in most job shops.

jon

"I may have many faults, but being wrong ain't one of them." Jimmy
Hoffa

On 21 Dec 2005 20:58:03 -0800, "jon_banquer"
wrote:

Perhaps to be fair we should mention using a Volstro milling head
attachment. Using one in the past has saved me a lot of time.

Perhaps you could learn about using a CNC .. get some
training or something. Any trade schools nearby?
--
Cliff