I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Searcher7 wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

All depends on the actual plastic you're dealing with. Some can be
worked like metal, some are gummy and soft and hard to handle while
others are brittle and any odd stresses cause them to shatter.


--
Steve W.

On Nov 14, 2:55*am, Searcher7 wrote:

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

With experience you can have good accuracy. I visited a one man shop
that only machined plastics and as I remember he could hold tolerances
of + - .oo1.

Sharp tools, lots of clearance , and expect to make some parts that
are out of tolerance until you get things dialed in.


Dan

On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7
wrote:

I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.
Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.

On Mon, 14 Nov 2011 08:08:05 -0800, Searcher7 wrote:

On Nov 14, 10:39Â*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, Â*etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and Acetron
for example) will release formaldehyde gas when heated too much. This
gas is corrisive as well as stinky and poisonous. Acetron can be
knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the plastics
but comes off with the proper soaps. Oil must be kept away from
acrylic. It will cause cracks. The cracks may not show for hours or
days, or maybe not until the plastic is stressed. Sharp positive rake
tools work best for most plastics. Nylon absorbs water so if it's going
to be used as a water lubricated bearing it should be roughed and then
soaked in water a couple days before finish machining. ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

My experience with PTFE and similar plastics is that if you just want to
whack things out and you don't need super high tolerances, you can just
use your regular metalworking cutters.

I do mostly hobby stuff and rough prototypes, so I've never needed to
attain high precision -- one of the nice things about PTFE and similar is
that it's pretty compliant, which means that you can make pegs oversized
and holes undersized, and when you push hard enough it all assembles just
fine.

--
www.wescottdesign.com

On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7
wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.

Use air as a coolant (if needed) and a nice sharp HSS tool.

Its not rocket science with nylon.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Nov 14, 3:33*pm, Gunner Asch wrote:
On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7



wrote:
On Nov 14, 10:39 am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.

Use air as a coolant (if needed) and a nice sharp HSS tool.

Its not rocket science with nylon.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
* * * * * * * * * * * * * * * * * *Gunner Asch

I suspect one of those air-powered Vortex cooling units would be real
handy when machining plastics.

On 11/14/2011 10:08 AM, Searcher7 wrote:

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.
Since most plastics have VERY low heat conductivity, you have to work
hard to keep it cool. Taking light cuts with very high feedrates
is most of the secret.

Jon

On Mon, 14 Nov 2011 13:37:37 -0800 (PST), Rex
wrote:

On Nov 14, 3:33*pm, Gunner Asch wrote:
On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7



wrote:
On Nov 14, 10:39 am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.

Use air as a coolant (if needed) and a nice sharp HSS tool.

Its not rocket science with nylon.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
* * * * * * * * * * * * * * * * * *Gunner Asch

I suspect one of those air-powered Vortex cooling units would be real
handy when machining plastics.

Some plastics indeed. However with nylon..and the small features
shown..there wouldnt be much heat involved and the air would be more for
stringy control than anything else. A basic form tool, with a bit of
positive rake and voila..high speed machining with mounds and mounds of
long stringy chips to try to keep off the spindle, the ways, the
operator etc etc. G

Ive got shops running my OmniTurns on nylon..and they set a 55 gallon
drum next to the machine and as the cutter hits the work..they grab the
stringer and stick the end into the trash can..and the rest of it
follows all by its lonesome. On big parts..its amusing to watch that
long white ribbon coming out of the machine, high overhead in a big arch
and into the trash can outside the machine.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Mon, 14 Nov 2011 13:37:37 -0800 (PST), Rex
wrote:

I suspect one of those air-powered Vortex cooling units would be real
handy when machining plastics.

I think I read somewhere that those can be made at home fairly easily.
Not quite up to the efficiency of professionally made ones, but good
enough to be useful.

The full name of the device is "Hilsch Vortex Tube". A Google search
brings up some interesting hits, such as:
http://www.instructables.com/id/The-Hilsch-vortex-tube/
--
RoRo

Robert Roland wrote in
:

On Mon, 14 Nov 2011 13:37:37 -0800 (PST), Rex
wrote:

I suspect one of those air-powered Vortex cooling units would be real
handy when machining plastics.

I think I read somewhere that those can be made at home fairly easily.
Not quite up to the efficiency of professionally made ones, but good
enough to be useful.

The full name of the device is "Hilsch Vortex Tube". A Google search
brings up some interesting hits, such as:
http://www.instructables.com/id/The-Hilsch-vortex-tube/

The problem is that they take a lot more air than most home shops can
supply. Lots of CFM at moderately high pressures.

Doug White

Doug White fired this volley in
:

The problem is that they take a lot more air than most home shops can
supply. Lots of CFM at moderately high pressures.

4cfm shouldn't be much past the ordinary HSM's compressor.

LLoyd

On 2011-11-14, Searcher7 wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

Yes.

I assume that as long as melting your way through the stock is not an
issue then it is ok.

Note that some materials will pinch down on a drilled hole, and
otherwise make things more difficult. The main trick is to use *very*
sharp tooling and tune the speed just right. Too fast and you will
overheat the material and it will start to melt and string out. Too
slow, and it will probably pinch more.

Delrin is my favorite of the plastics to machine. (And also
rather expensive compared to some.)

You don't mention Teflon -- which is a nice material to act as a
low-speed bearing, but again will be somewhat hygroscopic (as described
later), so will change dimensions and get tighter or looser.

But is it plausible to expect decent accuracy/tolerances this way?

Define "decent accuracy/tolerances". Most plastics will retreat
from the cutter somewhat, and spring back. This is why the sharpest
tools are the best here.

Nylon (and some others) are hygroscopic -- they absorb water from
the atmosphere, and change dimensions based on that. They also give up
water to the atmosphere when the humidity is low -- changing dimensions
in the other direction.

Look up the characteristics of the materials on web sites to
have an idea what to expect.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2011-11-14, Searcher7 wrote:
On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

[ ... ]

I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and

[ ... ]

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

Mostly not a problem. On a lathe, you will get big balls of
strings from turning most plastics, but they can be pulled away by hand
once the lathe is stopped.

Push a drill or some other tools too hard into plastic, and you
will have the flutes fill with melted plastic, but once it cools, you
can usually chip it off with no harm to the tool bit itself.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

How precise do the grooves need to be. (Both the width and the
spacing of the grooves.) That is the most hygroscopic of the materials
which you have mentioned, so it will change dimensions somewhat. You
may need to machine under maximum humidity or machine the grooves
oversized to keep clearance.

I, personally, would use either a horizontal mill with a
conventional milling cutter (not an end mill), or a shaper with a tool
hand ground to the right width and to optimum sharpness.

You can use a two-flute end mill to do it -- but your speed will
be more of a problem (risk of melting the Nylon and spoiling the
workpiece). The depth is shallow enough compared to the diameter of the
end mill so you should be able to do this in one pass. I doubt that you
can set up with a liquid coolant (if you are still in your apartment),
but you might be able to use compressed air to both remove the chips and
to cool the end mill and the plastic. (There are things available which
will turn compressed air into a flow of cold air out one end to cool the
workpiece, and dump hot air out the other end which you will have to
live with, because the hot air is produced by the process which also
produces the cold air. But they take a *lot* of airflow, and you may
not be able to run a compressor that powerful in your apartment. If
you've gotten a shop space somewhere, your options are increased. Here
are some examples on eBay:

# 110772235707 (two of them for $150.00 starting bid for the two)

# 290376851464 (single one for $144.00)

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7
wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

I assume that as long as melting your way through the stock is not an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.

Greetings Darren,
I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and
Acetron for example) will release formaldehyde gas when heated too
much. This gas is corrisive as well as stinky and poisonous. Acetron
can be knurled with standard bump knurls. It deforms remarkably well.
Different plastics require different coolants. Water for acrylics,
soluble oil for nylon, uhmw, acetal. The oil does stick to the
plastics but comes off with the proper soaps. Oil must be kept away
from acrylic. It will cause cracks. The cracks may not show for hours
or days, or maybe not until the plastic is stressed. Sharp positive
rake tools work best for most plastics. Nylon absorbs water so if it's
going to be used as a water lubricated bearing it should be roughed
and then soaked in water a couple days before finish machining.
ERic

Thanks everyone.

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

Darren Harris
Staten Island, New York.
That slot will be easy. You can probably get away with just an air
blast to remove the chips and keep things cool. To insure a good
finish and accurate size use an undersized endmill, 5/32 would be
good, and climb cut both sides of the slot instead of just plunging in
with a 3/16 cutter. But at such a shallow depth you might get away
with 1 pass with a 3/16 cutter. Just make sure you use a sharp cutter.
To help with getting a good finish on the bottom of the slot stone a
small radius on the sharp corners of a new endmill. .005 radius is
adequate. Can your slots have a small radius in the corners? If you
use a brand new cutter with sharp corners the bottom of the slot may
end up kind of furry.
ERic

On Nov 14, 9:59*pm, "DoN. Nichols" wrote:
On 2011-11-14, Searcher7 wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

* * * * [ ... ]

I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and

* * * * [ ... ]

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

* * * * Mostly not a problem. *On a lathe, you will get big balls of
strings from turning most plastics, but they can be pulled away by hand
once the lathe is stopped.

* * * * Push a drill or some other tools too hard into plastic, and you
will have the flutes fill with melted plastic, but once it cools, you
can usually chip it off with no harm to the tool bit itself.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

* * * * How precise do the grooves need to be. (Both the width and the
spacing of the grooves.) *That is the most hygroscopic of the materials
which you have mentioned, so it will change dimensions somewhat. *You
may need to machine under maximum humidity or machine the grooves
oversized to keep clearance.

* * * * I, personally, would use either a horizontal mill with a
conventional milling cutter (not an end mill), or a shaper with a tool
hand ground to the right width and to optimum sharpness.

* * * * You can use a two-flute end mill to do it -- but your speed will
be more of a problem (risk of melting the Nylon and spoiling the
workpiece). *The depth is shallow enough compared to the diameter of the
end mill so you should be able to do this in one pass. *I doubt that you
can set up with a liquid coolant (if you are still in your apartment),
but you might be able to use compressed air to both remove the chips and
to cool the end mill and the plastic. *(There are things available which
will turn compressed air into a flow of cold air out one end to cool the
workpiece, and dump hot air out the other end which you will have to
live with, because the hot air is produced by the process which also
produces the cold air. *But they take a *lot* of airflow, and you may
not be able to run a compressor that powerful in your apartment. *If
you've gotten a shop space somewhere, your options are increased. *Here
are some examples on eBay:

* * * * # 110772235707 (two of them for $150.00 starting bid for the two)

* * * * # 290376851464 (single one for $144.00)

* * * * Good Luck,
* * * * * * * * DoN.

--
* * * * * * * * * Remove oil spill source from e-mail
*Email: * | Voice (all times): (703) 938-4564
* * * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---

Thanks everyone.

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

I guess my mini mill(with sharp 3/8" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

BTW. I use this chart to get an idea of the properties of the plastics
I tend to have:
http://www.machinist-materials.com/c...r_plastics.htm

Thanks again.

Darren Harris
Staten Island, New York.

On Nov 14, 9:59*pm, "DoN. Nichols" wrote:
On 2011-11-14, Searcher7 wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

* * * * [ ... ]

I machine lots of plastics on machine tools made for metal. It's
important to keep the plastic cool. Acetal plastics (Delrin and

* * * * [ ... ]

I'm working on quite of few projects involving plastics and I guess my
biggest concern was gumming up my metal working tools.

* * * * Mostly not a problem. *On a lathe, you will get big balls of
strings from turning most plastics, but they can be pulled away by hand
once the lathe is stopped.

* * * * Push a drill or some other tools too hard into plastic, and you
will have the flutes fill with melted plastic, but once it cools, you
can usually chip it off with no harm to the tool bit itself.

My immediate concern is a project that involves creating a series of
3/16" wide and 1/16" deep grooves in Nylon at 1/8" intervals, and I'm
trying to figure out the best way to do this.

* * * * How precise do the grooves need to be. (Both the width and the
spacing of the grooves.) *That is the most hygroscopic of the materials
which you have mentioned, so it will change dimensions somewhat. *You
may need to machine under maximum humidity or machine the grooves
oversized to keep clearance.

* * * * I, personally, would use either a horizontal mill with a
conventional milling cutter (not an end mill), or a shaper with a tool
hand ground to the right width and to optimum sharpness.

* * * * You can use a two-flute end mill to do it -- but your speed will
be more of a problem (risk of melting the Nylon and spoiling the
workpiece). *The depth is shallow enough compared to the diameter of the
end mill so you should be able to do this in one pass. *I doubt that you
can set up with a liquid coolant (if you are still in your apartment),
but you might be able to use compressed air to both remove the chips and
to cool the end mill and the plastic. *(There are things available which
will turn compressed air into a flow of cold air out one end to cool the
workpiece, and dump hot air out the other end which you will have to
live with, because the hot air is produced by the process which also
produces the cold air. *But they take a *lot* of airflow, and you may
not be able to run a compressor that powerful in your apartment. *If
you've gotten a shop space somewhere, your options are increased. *Here
are some examples on eBay:

* * * * # 110772235707 (two of them for $150.00 starting bid for the two)

* * * * # 290376851464 (single one for $144.00)

* * * * Good Luck,
* * * * * * * * DoN.

--
* * * * * * * * * Remove oil spill source from e-mail
*Email: * | Voice (all times): (703) 938-4564
* * * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---

Thanks everyone.

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

I guess my mini mill(with sharp 3/16" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

BTW. I use this chart to get an idea of the properties of the plastics
I tend to have:
http://www.machinist-materials.com/c...r_plastics.htm

Thanks again.

(P.S.: Sorry if you received this twice. I had to make a correction in
the measurements, and I only post and view via Google Groups).

Darren Harris
Staten Island, New York.

On 2011-11-15, Searcher7 wrote:

[ ... ]

Thanks everyone.

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

O.K.

If you were working with high frequency RF, Teflon makes a
wonderful insulator, but is probably overkill for the machines you are
working-with/modifying/making.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

You probably want the grooves slightly oversized to give the
fingers room to spring.

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

O.K. Just two contacts per, then. Sort of like this as an end
view?

+---------------+
| |
| |
| |
| |
| |
+---------------+

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

I would suggest that would be preferred, since that will let you
go a little too thick and make a nicer finish with the mill before you
turn it to mill the grooves.

As for the mill to use -- use a *brand-new* end mill for this so
it is at its sharpest, and later use those for metal working while you
move newer ones into the plastic milling game.

I guess my mini mill(with sharp 3/8" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).

Yes -- that makes a difference.

You might, if you clamp the plastic to the mill's table with the
two sides to be grooved on front and back edges, try a 1/4" woodruff key
cutter (if you can find one that big) which would be closer to the
horizontal mill cutter which I said I would use by preference.

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

Understood. Compare it to Teflon. :-)

BTW. I use this chart to get an idea of the properties of the plastics
I tend to have:
http://www.machinist-materials.com/c...r_plastics.htm

Useful -- though I did not notice the change in dimensions when
exposed to water -- may have been there, I got tired of scrolling around
the page. A printed copy of the right size would be easier to work
with.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in
. 3.70:

Doug White fired this volley in
:

The problem is that they take a lot more air than most home shops can
supply. Lots of CFM at moderately high pressures.

4cfm shouldn't be much past the ordinary HSM's compressor.

Maybe they've gotten more efficient, but the commercial ones I looked at
years ago wanted 8+ CFM at 80 PSI or better.

Doug White

wrote in news:qhn3c7psi4auog48k4bhppb63rvdulbrj8@
4ax.com:

On Mon, 14 Nov 2011 08:08:05 -0800 (PST), Searcher7
wrote:

On Nov 14, 10:39*am, wrote:
On Sun, 13 Nov 2011 23:55:51 -0800 (PST), Searcher7

wrote:
I was wondering if it was common to use powered metalworking tools
on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, *etc.).

I assume that as long as melting your way through the stock is not
an
issue then it is ok.

But is it plausible to expect decent accuracy/tolerances this way?

Thanks.

Darren Harris
Staten Island, New York.
snip
That slot will be easy. You can probably get away with just an air
blast to remove the chips and keep things cool. To insure a good
finish and accurate size use an undersized endmill, 5/32 would be
good, and climb cut both sides of the slot instead of just plunging in
with a 3/16 cutter. But at such a shallow depth you might get away
with 1 pass with a 3/16 cutter. Just make sure you use a sharp cutter.
To help with getting a good finish on the bottom of the slot stone a
small radius on the sharp corners of a new endmill. .005 radius is
adequate. Can your slots have a small radius in the corners? If you
use a brand new cutter with sharp corners the bottom of the slot may
end up kind of furry.

Rather than an air blast, use a vacuum cleaner with a small nozzle to get
a good velocity. It will help keep the cutter a little cooler, and it
also keeps the stringy chips from piling up.

Doug White

Its possible. But for best results, there are optimum cutter angles that are
different for plastics than for metal. Drill bits, for example, have a
somewhat sharper point than those for steel.

If you want to pick nits, there are optimum cutter angles for different
kinds of metals as well as different plastics.

--
Paul Hovnanian
------------------------------------------------------------------
You can discover what your enemy fears most by observing the
means he uses to frighten you. -- Eric Hoffer

On Nov 15, 12:24*am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

* * * * [ ... ]

Thanks everyone.

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

* * * * O.K.

* * * * If you were working with high frequency RF, Teflon makes a
wonderful insulator, but is probably overkill for the machines you are
working-with/modifying/making.

I'll be running minor voltages (+3.3, +5, +12, +24 -5, -12) through
the contacts.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

* * * * You probably want the grooves slightly oversized to give the
fingers room to spring.

Yes. I may lay a 1/16" Nitrile or Styrene Butadiene/Natural Rubber
blend pad in between the block and contacts to keep the contact
consistent between all of contacts of two opposing blocks during heavy
vibration.

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

* * * * O.K. *Just two contacts per, then. *Sort of like this as an end
view?

* +---------------+
* | * * * * * * * |
* *| * * * * * * |
* *| * * * * * * |
* *| * * * * * * |
* | * * * * * * * |
* +---------------+

I'm not sure I get the ASCII above, but here a drawing of the flat
surface of a contact block and a contact block with the strips laid
across and bent down into it's grooves:
http://i290.photobucket.com/albums/l...ntactBlock.jpg

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

* * * * I would suggest that would be preferred, since that will let you
go a little too thick and make a nicer finish with the mill before you
turn it to mill the grooves.

I figure I can use a hand file to clean up if needed.

I guess my mini mill(with sharp 3/8" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).

* * * * Yes -- that makes a difference.

* * * * You might, if you clamp the plastic to the mill's table with the
two sides to be grooved on front and back edges, try a 1/4" woodruff key
cutter (if you can find one that big) which would be closer to the
horizontal mill cutter which I said I would use by preference.

I can't seem to picture what you're saying, but I assume a woodruff
key cutter would create a flat bottom groove. (Since these blocks will
only be 4-1/2" long, it looks as though I will definitely go with the
1/16" spacing between grooves in order to fit all 16 on each block.
(The blocks will be clamped by the grooved sides anyway).

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

* * * * Understood. *Compare it to Teflon. :-)

I had some opportunities to pick some up relatively cheap, but didn't
foresee any use for it at the time. :-)

Thanks.

Darren Harris
Staten Island, New York.

"Paul Hovnanian P.E." fired this volley in
diainc:

Drill bits, for example, have a
somewhat sharper point than those for steel.

and often a zero or slightly negative rake to prevent hogging and self-
feeding.

Lloyd

Searcher7 wrote:

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).
....

In that case, I would look into using a table saw. For cuts that
shallow, heating should not be a problem. Accuracy should be enough.
WAY faster than any metalworking approach.

Bob

On Nov 15, 2:58*pm, Bob Engelhardt wrote:
Searcher7 wrote:

To answer the questions, the grooves I have to make don't need to have
near perfect tolerances. I'm creating the grooves to place 3/16" wide
phosphor-Bronze strips in them for new contact blocks I'm making.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

...

In that case, I would look into using a table saw. *For cuts that
shallow, heating should not be a problem. *Accuracy should be enough.
WAY faster than any metalworking approach.

Bob

I don't see how that would be faster. Do you know of a jig that would
allow me to make a groove and then *quickly* shift the work over 1/4"
for the next groove until all 16 are done?

Thanks.

Darren Harris
Staten Island, New York.

DoN. Nichols wrote:
On 2011-11-14, Searcher7 wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

Yes.

I assume that as long as melting your way through the stock is not an
issue then it is ok.

Note that some materials will pinch down on a drilled hole, and
otherwise make things more difficult. The main trick is to use *very*
sharp tooling and tune the speed just right. Too fast and you will

I'm not a machinist by any measure, but I found that on a tiny lathe with
UMHW, just using the back of a 1/4" HSS cutter blank slighly sharpened to
the 15 degree angle they come at worked the best for what I was doing.
This left left a perfect finish on the plastic and the chip or whatever.

sharp pointed cutting surfaces left grooves and tended to pull the
material into the cutter. I made some tools that were curved, like a spoon
and they still didn't work at nice as the end of a blank. I was just
turning some rods down in diameter and facing off the ends.

Searcher7 wrote:
On Nov 15, 2:58 pm, Bob Engelhardt wrote:
In that case, I would look into using a table saw. ...

I don't see how that would be faster. Do you know of a jig that would
allow me to make a groove and then *quickly* shift the work over 1/4"
for the next groove until all 16 are done?

Sure, here's one that I made in 5 minutes:
http://home.comcast.net/~bobengelhardt/CuttingJig.jpg

The arrowed blob is a screw stub 1/4" o.c. from the kerf.
To use, make a first cut anywhere. For the 2nd cut, register the 1st
cut on the screw stub & cut. Repeat. The jig would be screwed to your
mitre guage. A couple of seconds per cut.

As you can see, this prototype didn't keep the spacing very accurately.
That was because the screw had very little bite in the 1/4" plywood
base and wobbled. Better would be to replace the screw with a glued
strip of wood, or something.

Bob

On Tue, 15 Nov 2011 23:10:00 +0000 (UTC), Cydrome Leader
wrote:

DoN. Nichols wrote:
On 2011-11-14, Searcher7 wrote:
I was wondering if it was common to use powered metalworking tools on
plastic.(Nylon, Delrin, ABS, UHMW, PVC, etc.).

Yes.

I assume that as long as melting your way through the stock is not an
issue then it is ok.

Note that some materials will pinch down on a drilled hole, and
otherwise make things more difficult. The main trick is to use *very*
sharp tooling and tune the speed just right. Too fast and you will

I'm not a machinist by any measure, but I found that on a tiny lathe with
UMHW, just using the back of a 1/4" HSS cutter blank slighly sharpened to
the 15 degree angle they come at worked the best for what I was doing.
This left left a perfect finish on the plastic and the chip or whatever.

sharp pointed cutting surfaces left grooves and tended to pull the
material into the cutter. I made some tools that were curved, like a spoon
and they still didn't work at nice as the end of a blank. I was just
turning some rods down in diameter and facing off the ends.

Also for plastics...the flutes on a 2 flute endmill are marvelous for
turning tools. Either run it backwards..or find some lefthanded endmills

The spiral makes it very easy to move the stringers.


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On 2011-11-15, Searcher7 wrote:
On Nov 15, 12:24*am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

[ ... ]

* * * * O.K.

* * * * If you were working with high frequency RF, Teflon makes a
wonderful insulator, but is probably overkill for the machines you are
working-with/modifying/making.

I'll be running minor voltages (+3.3, +5, +12, +24 -5, -12) through
the contacts.

Certainly not enough to justify using Teflon.

Making the grooves over-sized wouldn't be a problem because the 1/8"
distance between them is flexible. (In fact I may just go with 1/16"
between each groove).

* * * * You probably want the grooves slightly oversized to give the
fingers room to spring.

Yes. I may lay a 1/16" Nitrile or Styrene Butadiene/Natural Rubber
blend pad in between the block and contacts to keep the contact
consistent between all of contacts of two opposing blocks during heavy
vibration.

That -- or bend the contacts so they bow up in the middle of
their length.

The grooves, are just to make sure the strips don't shift. The
finished nylon pieces will be 4-1/2" long, 3/4" wide, and 1/4" thick,
and the grooves will be on the opposite 1/4" sides. Each strip will
wrap around into it's own groove.(Which will probably be the toughest
part of this project).

* * * * O.K. *Just two contacts per, then. *Sort of like this as an end
view?

* +---------------+
* | * * * * * * * |
* *| * * * * * * |
* *| * * * * * * |
* *| * * * * * * |
* | * * * * * * * |
* +---------------+

I'm not sure I get the ASCII above, but here a drawing of the flat
surface of a contact block and a contact block with the strips laid
across and bent down into it's grooves:
http://i290.photobucket.com/albums/l...ntactBlock.jpg

O.K. Very different from what I was interpreting your text as
saying. Be sure to view this with a fixed pitch font (like Courier) to
keep the drawing from being distorted

/ / /
/ / / //
/ / / ///
* +---------------+ / ///
* | * * * * * * * |/ ///
* *| * * * * * * | ///
* *| * * * * * * | ///
* *| * * * * * * |///
* | * * * * * * * |/
* +---------------+

As I was drawing it, the (now added) diagonal lines would go
along the 4.5" length, the 3/4" width would be the horizontal dimension,
and the 1/4" would be the vertical dimension -- giving only room for a
single strip on each side.

Obviously not what you intended to say.

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

* * * * I would suggest that would be preferred, since that will let you
go a little too thick and make a nicer finish with the mill before you
turn it to mill the grooves.

I figure I can use a hand file to clean up if needed.

You may want to make something too thick and finish with the
mill (or a metalworking shaper if you had one).

I guess my mini mill(with sharp 3/8" end mills) is the best machine
for the grooving job, out of the what I have. (I just have to get it
fixed first).

* * * * Yes -- that makes a difference.

* * * * You might, if you clamp the plastic to the mill's table with the
two sides to be grooved on front and back edges, try a 1/4" woodruff key
cutter (if you can find one that big) which would be closer to the
horizontal mill cutter which I said I would use by preference.

I can't seem to picture what you're saying, but I assume a woodruff
key cutter would create a flat bottom groove. (Since these blocks will
only be 4-1/2" long, it looks as though I will definitely go with the
1/16" spacing between grooves in order to fit all 16 on each block.
(The blocks will be clamped by the grooved sides anyway).

A Woodruff key cutter is normally used to make a cut in the side
of a shaft which is like a ')' in profile, into which a Woodruff key
(like a slice off the edge of a coin) is placed, and part of it projects
above the shaft to engage a groove in the pulley or gear on the shaft to
prevent them slipping around the shaft.

However -- the cutter is *not* right for cutting the grooves in
the direction you want. It does not have a long enough shank to reach
along your shaft in the 4-1/2" dimension. I was assuming that the
groove was parallel to the 4-1/2" dimension, in which case a Woodruff
key cutter could do a nice job on either side of a piece of plastic
clamped down to the table -- *not* in a vise.

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

* * * * Understood. *Compare it to Teflon. :-)

I had some opportunities to pick some up relatively cheap, but didn't
foresee any use for it at the time. :-)

Too good for your task, unless you need the low friction
features of it. You aren't working with high frequencies, and certainly
not with high voltages (2 kV to maybe 60 kV. :-)

Nylon should be fine for what you are doing.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote:

Searcher7 wrote:

Yes. I may lay a 1/16" Nitrile or Styrene Butadiene/Natural Rubber
blend pad in between the block and contacts to keep the contact
consistent between all of contacts of two opposing blocks during heavy
vibration.

That -- or bend the contacts so they bow up in the middle of
their length.


How about using pieces of 'phosphor bronze finger stock' or 'pogo
pins'?


--
You can't have a sense of humor, if you have no sense.

On Nov 15, 7:40*pm, Bob Engelhardt wrote:
Searcher7 wrote:
On Nov 15, 2:58 pm, Bob Engelhardt wrote:
In that case, I would look into using a table saw. *...
I don't see how that would be faster. Do you know of a jig that would
allow me to make a groove and then *quickly* shift the work over 1/4"
for the next groove until all 16 are done?

Sure, here's one that I made in 5 minutes:http://home.comcast.net/~bobengelhardt/CuttingJig.jpg

The arrowed blob is a screw stub 1/4" o.c. from the kerf.
To use, make a first cut anywhere. *For the 2nd cut, register the 1st
cut on the screw stub & cut. *Repeat. *The jig would be screwed to your
mitre guage. *A couple of seconds per cut.

As you can see, this prototype didn't keep the spacing very accurately.
* That was because the screw had very little bite in the 1/4" plywood
base and wobbled. *Better would be to replace the screw with a glued
strip of wood, or something.

Bob

Ok, thanks.

I wasn't think in terms of using my woodworking equipment also. :-)

Unfortunately, my table saw sounds like a Jumbo jet and my window of
opportunity closed when new neighbors moved in below me at the
beginning of the month.

But perhaps my router table will suffice. Unlike the cheap Delta table
saw I have, I have a miter gauge for it. (The table saw has unorthodox
miter gauge slot dimensions and therefore I'd have to make some
runners for it).

I do have a mini table saw that is about half the size of a bread
box. :-) But I doubt I'd find a blade thick enough to make 3/16"
grooves.

Thanks.

Darren Harris
Staten Island, New York.

On Nov 16, 12:11 am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

On Nov 15, 12:24 am, "DoN. Nichols" wrote:
On 2011-11-15, Searcher7 wrote:

Yes. I may lay a 1/16" Nitrile or Styrene Butadiene/Natural Rubber
blend pad in between the block and contacts to keep the contact
consistent between all of contacts of two opposing blocks during heavy
vibration.

That -- or bend the contacts so they bow up in the middle of
their length.

Well, if the contacts were to be secured by only one end, then I'd
just let them bounce like a diving board, resulting in less metal
fatigue. But, the wiping action I'm incorporating must allow for both
directions across the contacts, which is why both ends of each contact
has to be secured.

The *structure* the contact blocks will be permanently attached to
will be wood, which must come together tightly and locked into place.
Something like rubber will account for any expansion/contraction of
the structure under conditions of varying humidity.

O.K. Very different from what I was interpreting your text as
saying. Be sure to view this with a fixed pitch font (like Courier) to
keep the drawing from being distorted

/ / /
/ / / //
/ / / ///
+---------------+ / ///
| |/ ///
| | ///
| | ///
| |///
| |/
+---------------+

As I was drawing it, the (now added) diagonal lines would go
along the 4.5" length, the 3/4" width would be the horizontal dimension,
and the 1/4" would be the vertical dimension -- giving only room for a
single strip on each side.

Obviously not what you intended to say.

Ok. The 3-D image makes things clearer.

I was hoping that cooling would not be an issue because I'll basically
be making a 4-1/2" long grooves, moving over about 1/8", and then
repeating for a total of 16 of these grooves. I can then cut off 1/4"
thick slices with my band saw. (The other alternative is to cut off
the 1/4" thick slices first and make the grooves in each piece). :-)

I would suggest that would be preferred, since that will let you
go a little too thick and make a nicer finish with the mill before you
turn it to mill the grooves.

I figure I can use a hand file to clean up if needed.

You may want to make something too thick and finish with the
mill (or a metalworking shaper if you had one).

I'm not averse to hand tools. :-) (Which is preferable considering my
present living environment). :-)

A Woodruff key cutter is normally used to make a cut in the side
of a shaft which is like a ')' in profile, into which a Woodruff key
(like a slice off the edge of a coin) is placed, and part of it projects
above the shaft to engage a groove in the pulley or gear on the shaft to
prevent them slipping around the shaft.

However -- the cutter is *not* right for cutting the grooves in
the direction you want. It does not have a long enough shank to reach
along your shaft in the 4-1/2" dimension. I was assuming that the
groove was parallel to the 4-1/2" dimension, in which case a Woodruff
key cutter could do a nice job on either side of a piece of plastic
clamped down to the table -- *not* in a vise.

Ok. But I'll keep those in mind when I have to make a keyway in
something like a motor shaft.

I have a lot of Delrin, which is also my favorite, but I like to save
it for the critical stuff, since it is not cheap. :-)

Understood. Compare it to Teflon. :-)

I had some opportunities to pick some up relatively cheap, but didn't
foresee any use for it at the time. :-)

Too good for your task, unless you need the low friction
features of it. You aren't working with high frequencies, and certainly
not with high voltages (2 kV to maybe 60 kV. :-)

Nylon should be fine for what you are doing.

Yes. And Delrin has always been good enough for those low friction
needs or for when dimensional stability is needed.

Thanks a lot.

Darren Harris
Staten Island, New York.

On Thu, 17 Nov 2011 14:21:09 -0800 (PST), Searcher7
wrote:

On Nov 15, 7:40*pm, Bob Engelhardt wrote:
Searcher7 wrote:
On Nov 15, 2:58 pm, Bob Engelhardt wrote:
In that case, I would look into using a table saw. *...
I don't see how that would be faster. Do you know of a jig that would
allow me to make a groove and then *quickly* shift the work over 1/4"
for the next groove until all 16 are done?

Sure, here's one that I made in 5 minutes:http://home.comcast.net/~bobengelhardt/CuttingJig.jpg

The arrowed blob is a screw stub 1/4" o.c. from the kerf.
To use, make a first cut anywhere. *For the 2nd cut, register the 1st
cut on the screw stub & cut. *Repeat. *The jig would be screwed to your
mitre guage. *A couple of seconds per cut.

As you can see, this prototype didn't keep the spacing very accurately.
* That was because the screw had very little bite in the 1/4" plywood
base and wobbled. *Better would be to replace the screw with a glued
strip of wood, or something.

Bob

Ok, thanks.

I wasn't think in terms of using my woodworking equipment also. :-)

Unfortunately, my table saw sounds like a Jumbo jet and my window of
opportunity closed when new neighbors moved in below me at the
beginning of the month.

But perhaps my router table will suffice. Unlike the cheap Delta table
saw I have, I have a miter gauge for it. (The table saw has unorthodox
miter gauge slot dimensions and therefore I'd have to make some
runners for it).

I do have a mini table saw that is about half the size of a bread
box. :-) But I doubt I'd find a blade thick enough to make 3/16"
grooves.

Thanks.

Darren Harris
Staten Island, New York.
Put 2 blades together?
Gerry :-)}
London, Canada

On Thu, 17 Nov 2011 20:27:17 -0500, Gerald Miller
wrote:

On Thu, 17 Nov 2011 14:21:09 -0800 (PST), Searcher7
wrote:
I do have a mini table saw that is about half the size of a bread
box. :-) But I doubt I'd find a blade thick enough to make 3/16"
grooves.

Build a jig for that, Darren. A 1/8" piece of lauan ply made into a
crosscut sled, with runners on the bottom to guide it over the mini
saw table top. Glue a tall strip on the far side, perpendicular to the
blade. The first cut puts the slot in the strip (fence) and sled. Now
mount a t-slot into the top of the fence and run a flip stop on it,
perhaps with flippable shims to allow the dado width.


Put 2 blades together?

Or, if he can find a really good glue...

[Disclaimer: Kids, don't try this at home!]

--
Most powerful is he who has himself in his own power.
-- Seneca