Today, I had to make some grippers for a machine that grasps a round part and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.

On Dec 2, 4:02*pm, Wes wrote:
Today, I had to make some grippers for a machine that grasps a round part and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. *I learned that drill bits don't make
on size holes nor do end mills. *Obviously, clamping forces have an effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.

That's an awfully small hole. If it was any larger, I would make a
hollow punch, like a leather or gasket punch,punch, and press it
through the rubber.

Paul

Wes wrote:
Today, I had to make some grippers for a machine that grasps a round part and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.



Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.

John

When I was in industrial research, the strategy was to freeze it in
liquid nitrogen. Then we could grind it. We were making drive pucks
for experimental tape recorders. You had to work fast!

"Wes" wrote in message
...
Today, I had to make some grippers for a machine that grasps a round part
and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill
bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect
on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.


I've cut thinner sheet goods on the lathe using two sided tape, a round wood
block in the chuck, and a blade in the tool post. The last time I had to
size smaller holes I made a hollow punch and a carrier for the blank. The
punch went in the tailstock chuck, slowly advanced it with the blank
turning. Went well..

"Wes" wrote in message
...
Today, I had to make some grippers for a machine that grasps a round part
and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill
bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect
on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.

Grind your bit so it looks like a wood bit. I used to drill larger holes in
rubber conveyor belt with a modified drill bit that looked like this.
http://www.highlandwoodworking.com/P...ing/077914.jpg
Steve

Any tips on machining rubber?

LN2 comes to mind as the ideal "fixative". Cheap, too.

LLoyd

At the tire factory they machine rubber at room temperature by grinding.
The "cutters" are like the carbide grit edge type, looks a metal
grinding/sanding wheel. Try an abrasive type bit in a high speed spindle,
like a Dremel tool or similar. The finish of a white wall and white letter
tires is one of the results of this type of grinding. You do have to
control the feed, perhaps some air to get the rubber dust clear. Our white
sidewall buffers blow air while the grinders are down.

RogerN

"Wes" wrote in message
...
Today, I had to make some grippers for a machine that grasps a round part
and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill
bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect
on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.

"John" wrote in message
...
Wes wrote:
Today, I had to make some grippers for a machine that grasps a round part
and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill
bits don't make
on size holes nor do end mills. Obviously, clamping forces have an
effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.



Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.

John

Not with all that rampant Global Warming out there!

I have successfully machined rubber on the lathe by grinding with the
tool post grinder. That's about the only thing that has worked
reliably for me. For your application, how about putting a small
grinding point in the Dremel?

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

Wes wrote:

Today, I had to make some grippers for a machine that grasps a round part and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.

On Dec 2, 7:15*pm, " wrote:
That's an awfully small hole. If it was any larger, I would make a
hollow punch, like a leather or gasket punch,punch, and press it
through the rubber.

Paul

This is the punch set chemists used to punch holes in cork and then
rubber stoppers:
http://www.boekelsci.com/pages/produ...ro_lab_06.html

The bevel is on the outside so the cut plug doesn't jam. The conical
handled tool with the swinging steel blade sharpens the cutters. Soap
is a good cutting lubricant.

jsw

" wrote:

That's an awfully small hole. If it was any larger, I would make a
hollow punch, like a leather or gasket punch,punch, and press it
through the rubber.


I needed to make a counter sink for a 8-32 SHCS in 1/2" thick material.


Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

John wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

"Up North" wrote:

Grind your bit so it looks like a wood bit. I used to drill larger holes in
rubber conveyor belt with a modified drill bit that looked like this.
http://www.highlandwoodworking.com/P...ing/077914.jpg
Steve

McMaster has some of those bits. Sadly, only by 16ths but I did order a few in my size
range to try. Thanks.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Wes wrote:
wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller


I guess you never chilled a six pack of beer with a co2 fire
extinguisher.

John

Wes wrote:
Today, I had to make some grippers for a machine that grasps a round part and then drives
6 bolts in to 50 lb/ft.

I was using some rubber with fabric re-inforcement. I learned that drill bits don't make
on size holes nor do end mills. Obviously, clamping forces have an effect on hole
diameter.

I ended up moving up in size until the 8-32 shcs fit.

This was one of those close enough applications.

Any tips on machining rubber?

Wes
--

The only thing Obama has fixed is Carter's reputation.






A piece of stainless steel tubing used as a drill bit should work too.
Sharpen the end by using a conical grinding burr on the inside of the
tubing. This will work if the material is not too thick.

John

Your local Gas supplier can have it to you via truck in a day or two.
The local one has done it regularly for a local machine shop.
I don't know the application - maybe metal working - rapid shrinkage
but might be various rubber product like items needing machining or pre-chilling.
Martin

Wes wrote:
John wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

John wrote:
Wes wrote:
wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design
to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for
welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller


I guess you never chilled a six pack of beer with a co2 fire
extinguisher.

John

I'm guessing you never have either.
It takes more like a six pack of extinguishers to cool one beer.

cavelamb wrote:
John wrote:
Wes wrote:
wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try
just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a
design to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for
welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller


I guess you never chilled a six pack of beer with a co2 fire
extinguisher.

John

I'm guessing you never have either.
It takes more like a six pack of extinguishers to cool one beer.

Not if it is a true co2 unit. A 20 pounder will take a 6 pack down to
about 40 degrees on an 80 plus day without a fuss. BTDT with units we
were taking out of service. Of course it was soda but hey it did the
job. I wouldn't use it as the method of choice though since that can get
VERY expensive real quick.




--
Steve W.

On Sat, 05 Dec 2009 21:39:38 -0600, cavelamb
wrote:

John wrote:
Wes wrote:
wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design
to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for
welding that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller


I guess you never chilled a six pack of beer with a co2 fire
extinguisher.

John

I'm guessing you never have either.
It takes more like a six pack of extinguishers to cool one beer.


Not if you put it in a 5 gallon bucket and hose down the inside of the
bucket.

Gunner, who has done this with soda as well.



"First Law of Leftist Debate
The more you present a leftist with factual evidence
that is counter to his preconceived world view and the
more difficult it becomes for him to refute it without
losing face the chance of him calling you a racist, bigot,
homophobe approaches infinity.

This is despite the thread you are in having not mentioned
race or sexual preference in any way that is relevant to
the subject." Grey Ghost

I was Chief Engineer of a brewing company in The Fiji Islands in the late
70's.
We always had at least 20 tonnes of CO2 on hand as it is collected from the
fermenters and re-injected later.
We often made dry ice by taking liquid CO2 from the storage tanks and
bleeding it through a fitting that had a number of mesh screens in it. It
came out as snow ( the commercial stuff is pressed into blocks) which we
would put into denatured alcohal. This would cool the alcohal down to about
minus 80 F, if I recall correctly. we used it several times to turn a few
thou off the rubber coated cylinders used in labelling machines. They were
set up on mandrels and replaced in the cold alcohal every few minutes as
they warmed up pretty quick. It wasn't an ideal solution as the finish
wasn't as good as I would have liked, but it kept us running until a new one
could be sent from Melbourne.

We used it a quite few times to shrink shafts so we could get bearings off.
Dip the lot in the cold pot,heat the bearing quickly with an oxy torch, hit
with a big hammer, and Bob's you uncle.

It also made a hell of a bang if you put a bit of it in a plastic Coke
bottle and sealed it up well.



"Wes" wrote in message
news
John wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design to
make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for welding
that I could
tap.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On Mon, 07 Dec 2009 10:59:41 +1100, Grumpy wrote:

On Mon, 07 Dec 2009 10:59:41 +1100, Grumpy top-posted:

I was Chief Engineer of a brewing company in The Fiji Islands in the late
70's.
We always had at least 20 tonnes of CO2 on hand as it is collected from
the fermenters and re-injected later.
We often made dry ice by taking liquid CO2 from the storage tanks and
bleeding it through a fitting that had a number of mesh screens in it. It
came out as snow ( the commercial stuff is pressed into blocks) which we
would put into denatured alcohal. This would cool the alcohal down to
about minus 80 F, if I recall correctly. we used it several times to turn
a few thou off the rubber coated cylinders used in labelling machines.
They were set up on mandrels and replaced in the cold alcohal every few
minutes as they warmed up pretty quick. It wasn't an ideal solution as the
finish wasn't as good as I would have liked, but it kept us running until
a new one could be sent from Melbourne.

We used it a quite few times to shrink shafts so we could get bearings
off.
Dip the lot in the cold pot,heat the bearing quickly with an oxy torch,
hit with a big hammer, and Bob's you uncle.

Freeze it with liquid nitrogen, then drill the holes. You could try just
putting it in the freeze depending on the type of rubber compound. or
just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a design
to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for
welding that I could
tap.

I once did this with some steel pins that had to be put in an aluminum
block, but I just put the pins in the company's freezer (a household
fridge in the kitchen), and heated up the aluminum block with a torch.

That worked well, too! :-)

Cheers!
Rich

Snip.

I once did this with some steel pins that had to be put in an aluminum
block, but I just put the pins in the company's freezer (a household
fridge in the kitchen), and heated up the aluminum block with a torch.

That worked well, too! :-)

Cheers!
Rich

Yep ! if they were a snug fit when you put them in, they'll be there fore
ever.

"Wes" wrote in message
news
John wrote:

Freeze it with liquid nitrogen, then drill the holes. You could try
just putting it in the freeze depending on the type of rubber
compound. or just wait a couple of weeks and put it outside.


I'm curious if dry ice would be good enough? Somewhere I saw a
design to make dry ice
using compressed CO2. Wish I could find it now. We have CO2 for
welding that I could
tap.

For small one-off jobs, I suspect spray freeze (electronic freon coolant
for checking for thermal problems) would work. You can get the same
effect by turning a can of "duster" freon upside down.

Doug White