Main Page | Report Page

 

  Hobby Forum Index » Models - Scale » drilling holes in soft open-cell foam

Author Message
Guest
Posted: Mon Feb 18, 2008 11:06 am
 
Does anyone have an advice on how to drill neat round holes in soft
open-cell foam/sponge (polyurethane)? I am trying to make ~1/4" holes
in a ~2 inch thick sponge. I tried regular drills (very ugly-looking
results, or the foam just gets wrapped around the drill) and an old
cork bore (the foam just gets squished). I need the holes to be neat
and see-through. Do they make hole saws with razor-sharp teeth?
 
Guest
Posted: Mon Feb 18, 2008 11:45 am
 
On Feb 18, 4:06�pm, runcyclexc...@gmail.com wrote:
Quote:
Does anyone have an advice on how to drill neat round holes in soft
open-cell foam/sponge (polyurethane)? I am trying to make ~1/4" holes
in a ~2 inch thick sponge. I tried regular drills (very ugly-looking
results, or the foam just gets wrapped around the drill) and an old
cork bore (the foam just gets squished). I need the holes to be neat
and see-through. Do they make hole saws with razor-sharp teeth?

Sounds as if you will need either a punch or you will have to burn
them through the sponge (as with a heated probe, not flame!). The
former method (IF you can find some good steel punches -- the kind
with hollow centers and a sharp beveled ring) will probably be the
best as the other tends to leave melted detrius around the holes.

Cookie Sewell
 
Guest
Posted: Mon Feb 18, 2008 12:34 pm
 
Quote:
I think they use hollow punches with a sharp edge, compress the foam,
then punch it.

I think this is the way to go

Quote:
If you don't mind the mess (and the smell, which is really bad with
polyurethane) you could heat up something metal of the diameter of the
hole size you want you want and melt it through, although this will
leave some goo

Yes, and I want to keep the cells open, while the burning, I imagine,
would seal at least some of the cells.

Thank you for the ideas!
 
Drew Hill
Posted: Mon Feb 18, 2008 12:51 pm
 
On Feb 18, 3:06 pm, runcyclexc...@gmail.com wrote:
Quote:
Does anyone have an advice on how to drill neat round holes in soft
open-cell foam/sponge (polyurethane)? I am trying to make ~1/4" holes
in a ~2 inch thick sponge. I tried regular drills (very ugly-looking
results, or the foam just gets wrapped around the drill) and an old
cork bore (the foam just gets squished). I need the holes to be neat
and see-through. Do they make hole saws with razor-sharp teeth?

Here's another idea: My dad says that he used to make holes in
foam rubber by soaking it in water (getting it full of water like a
sponge
does), freeze it, then drill a hole fairly quick right out of the
freezer.

You'll have to wait a heckuva long time for the water to drain and for
the foam to dry out afterwards

Hope this helps!


-andyh
 
Guest
Posted: Mon Feb 18, 2008 12:53 pm
 
Quote:
Here's another idea: My dad says that he used to make holes in
foam rubber by soaking it in water (getting it full of water like a
sponge
does), freeze it, then drill a hole fairly quick right out of the
freezer.


This is a really cool idea. I have access to liquid nitrogen and to a
-80C kelvinator - so it should be a piece of cake... I guess.
 
Pat Flannery
Posted: Mon Feb 18, 2008 6:23 pm
 
runcyclexcski@gmail.com wrote:
Quote:
Does anyone have an advice on how to drill neat round holes in soft
open-cell foam/sponge (polyurethane)? I am trying to make ~1/4" holes
in a ~2 inch thick sponge. I tried regular drills (very ugly-looking
results, or the foam just gets wrapped around the drill) and an old
cork bore (the foam just gets squished). I need the holes to be neat
and see-through. Do they make hole saws with razor-sharp teeth?


I think they use hollow punches with a sharp edge, compress the foam,
then punch it.
If you don't mind the mess (and the smell, which is really bad with
polyurethane) you could heat up something metal of the diameter of the
hole size you want you want and melt it through, although this will
leave some goo on the inside of the foam.
Don't get it too hot though; polyurethane will ignite and burn, and
emits toxic smoke when it does.

Pat
 
Pat Flannery
Posted: Mon Feb 18, 2008 6:35 pm
 
AMPSOne@aol.com wrote:
Quote:
The
former method (IF you can find some good steel punches -- the kind
with hollow centers and a sharp beveled ring)


Leather working shop; they have them.

Pat
 
Pat Flannery
Posted: Mon Feb 18, 2008 7:54 pm
 
runcyclexcski@gmail.com wrote:
Quote:
I think they use hollow punches with a sharp edge, compress the foam,
then punch it.


I think this is the way to go


If you don't mind the mess (and the smell, which is really bad with
polyurethane) you could heat up something metal of the diameter of the
hole size you want you want and melt it through, although this will
leave some goo


Yes, and I want to keep the cells open, while the burning, I imagine,
would seal at least some of the cells.


It also leaves a nasty oily residue as the chemicals in the foam break down.
You should be able to find a 1/4" punch fairly easily at a leather
working shop, and possibly at a good-sized fabric or hobby store also.
When you punch it, you probably want to do it on a piece of wood, so as
not to dull the punch after it cuts through the foam.


Pat
 
Pat Flannery
Posted: Mon Feb 18, 2008 7:58 pm
 
Drew Hill wrote:
Quote:
On Feb 18, 3:06 pm, runcyclexc...@gmail.com wrote:

Does anyone have an advice on how to drill neat round holes in soft
open-cell foam/sponge (polyurethane)? I am trying to make ~1/4" holes
in a ~2 inch thick sponge. I tried regular drills (very ugly-looking
results, or the foam just gets wrapped around the drill) and an old
cork bore (the foam just gets squished). I need the holes to be neat
and see-through. Do they make hole saws with razor-sharp teeth?


Here's another idea: My dad says that he used to make holes in
foam rubber by soaking it in water (getting it full of water like a
sponge
does), freeze it, then drill a hole fairly quick right out of the
freezer.


Boy! Now that's a clever idea...somebody was thinking outside the box on
that one.

Quote:
You'll have to wait a heckuva long time for the water to drain and for
the foam to dry out afterwards


You can dunk it in hot water after drilling it. That will melt out the ice.
After that, just squeeze out the water like a sponge.

Pat
 
Pat Flannery
Posted: Mon Feb 18, 2008 8:09 pm
 
runcyclexcski@gmail.com wrote:

Quote:

This is a really cool idea. I have access to liquid nitrogen

Watch out if you stick it in that; the warm water will make the liquid
nitrogen boil, and you don't want to get splashed with that.
I think the Kelvinator sounds a lot safer.
I imagine you could dip the foam with no water in it into the liquid
nitrogen and drill it after it was frozen, but something way in the back
of my mind keeps saying that some odd chemical reactions may result from
that... something associated with explosives.
Quote:
and to a
-80C kelvinator - so it should be a piece of cake... I guess.

You might want to take a piece of the dry foam and chill it down to -80

and see if that's drillable.

Pat
 
PaPaPeng
Posted: Mon Feb 18, 2008 8:33 pm
 
On Mon, 18 Feb 2008 14:53:50 -0800 (PST), runcyclexcski@gmail.com
wrote:

Quote:

Here's another idea: My dad says that he used to make holes in
foam rubber by soaking it in water (getting it full of water like a
sponge
does), freeze it, then drill a hole fairly quick right out of the
freezer.


This is a really cool idea. I have access to liquid nitrogen and to a
-80C kelvinator - so it should be a piece of cake... I guess.


Use a triangular corundum drill attachment bit to sharpen the inside
rim of a 1/4 inch tube. Use that as your foam drill bit. It might
help to notch the rim first (with a Dremel cutoff disc) to create
teeth before sharpening.
 
Guest
Posted: Tue Feb 19, 2008 12:35 pm
 
Freezing in a block of water and then milling is how aircraft
honeycomb panels are shaped. The honeycomb structure is very fragile
before it is skinned and this is the best way to create the required
shape.
 
Guest
Posted: Wed Feb 20, 2008 8:18 am
 
Quote:
Freezing in a block of water and then milling

I tried the freeze-and-drill method, and it worked.
 
z
Posted: Fri Feb 22, 2008 8:52 am
 
On Feb 18, 6:54pm, Pat Flannery <flan...@daktel.com> wrote:

Quote:
Yes, and I want to keep the cells open, while the burning, I imagine,
would seal at least some of the cells.

It also leaves a nasty oily residue as the chemicals in the foam break down.

ummm..... and emits cyanide gas.....
 
z
Posted: Fri Feb 22, 2008 8:54 am
 
On Feb 20, 1:18pm, runcyclexc...@gmail.com wrote:
Quote:
Freezing in a block of water and then milling

I tried the freeze-and-drill method, and it worked.

wow. always cool to learn a new technique. now i gotta think of what i
need it for.....
 
 
Page 1 of 2    Goto page 1, 2  Next
All times are GMT - 5 Hours
The time now is Thu Aug 21, 2014 3:06 pm