I'd like to machine a few (2 or 3) teflon gasket rings out of quarter
inch sheet stock. The ID needs to be roughly 50 mm, the OD about 60 mm
and thickness that of the stock. The only critical dimension is the OD,
which has to be a snug fit in the groove where it'll live.

The sheet stock is what I happen to have. Likely most people would start
with bar stock then turn, bore and part off.

It's been a couple decades since I last did this, and all I can remember was that fixturing was a bit of a pain. I think I turned the OD first, with the stock pinched between chuck jaw tips and tailstock, but I can't remember how
I held the resulting disk to bore the ID. It's way too soft to hold in a chuck.

Everything I can think of involves making at least one faceplace fixture and probably two. Can anybody point me to simpler methods? I'm not looking to save time so much as material; I'm retired, so time is cheap but it looks like any reasonable teflon stock will cost at least $100. And, it's good mental exercise.

Thanks for reading,

bob prohaska

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/11/2023 10:54 AM, Jim Wilkins wrote:

"bob prohaska"  wrote in message news:ul7ets$382no$1@dont-email.me...

I'd like to machine a few (2 or 3) teflon gasket rings out of quarter
inch sheet stock. The ID needs to be roughly 50 mm, the OD about 60 mm
and thickness that of the stock. The only critical dimension is the OD,
which has to be a snug fit in the groove where it'll live.

The sheet stock is what I happen to have. Likely most people would start
with bar stock then turn, bore and part off.

It's been a couple decades since I last did this, and all I can remember
was
that fixturing was a bit of a pain. I think I turned the OD first, with the stock pinched between chuck jaw tips and tailstock, but I can't remember
how
I held the resulting disk to bore the ID. It's way too soft to hold in a chuck.

Everything I can think of involves making at least one faceplace fixture
and
probably two. Can anybody point me to simpler methods? I'm not looking
to save
time so much as material; I'm retired, so time is cheap but it looks
like any
reasonable teflon stock will cost at least $100. And, it's good mental exercise.

Thanks for reading,

bob prohaska
----------------------
Holtzapffel's lathe book suggests turning ivory rings on a custom wood
plug or cup chuck. He claimed it would hold size for one day, perhaps
two unless the weather changed.

The plug chuck could be a snug fitting shouldered stub with the work
held on by tubing pressed against it by the tailstock, avoiding
expansion. If you don't have suitable tubing or don't need to check the
final fit repeatedly it could be held by screws and washers.

The outside chuck he suggests is a cup slotted into fingers and closed
with a ring sliding on an external taper. A simpler version could be a shallow locating recess surrounded by screws and washers that catch the
edge of the work.

Both ID and OD can be turned by screwing the blank to plywood on a
faceplate. Fender washers can be bent into low profile step clamps.
The lathe bit will cut its own clearance in the wood. This is simpler
but provides less radial support.

If the only critical dimension is the OD, I suggest punch a hole in it,
rough cut it round by any means, and then bolt it to the end of a
mandrel with a support washer/cap on the outside. Turn to size. Glues
won't stick to any significant degree, but they may mechanically hold it
just enough to help you take light passes while holding it lightly with
your cap. PTFE will distort if you reef down on the bolt.
--
Bob La Londe
CNC Molds N Stuff


--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Mon, 11 Dec 2023 16:55:24 -0000 (UTC)
bob prohaska <bp@www.zefox.net> wrote:

I'd like to machine a few (2 or 3) teflon gasket rings out of quarter
inch sheet stock. The ID needs to be roughly 50 mm, the OD about 60 mm
and thickness that of the stock. The only critical dimension is the OD, >which has to be a snug fit in the groove where it'll live.

<snip>

You can buy "gasket cutters" that can work on PTFE up to 1/4 inch. See
for an assortment:

https://www.mcmaster.com/products/gasket-cutters/

This one isn't priced too bad and might do the job🤷

https://www.mcmaster.com/36795A11

--
Leon Fisk
Grand Rapids MI

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Mon, 11 Dec 2023 14:36:12 -0500
"Jim Wilkins" <muratlanne@gmail.com> wrote:

"Leon Fisk" wrote in message news:ul7nf1$38ra1$1@dont-email.me...

You can buy "gasket cutters" that can work on PTFE up to 1/4 inch. See
for an assortment:

https://www.mcmaster.com/products/gasket-cutters/

This one isn't priced too bad and might do the job🤷

https://www.mcmaster.com/36795A11
Leon Fisk

----------------------------

If you've used one, how easy was it?

I haven't used one. Just know they exist🤷

I have used the "Hole Saw" which is built in a similar style:

https://www.mcmaster.com/products/hole-cutters/adjustable-diameter-hole-saws-for-sheet-metal-10/

They work pretty well in a drill press. I've cut parts from 1/4 inch
steel using one. That's probably close to their limit. Using them in
a hand drill is highly dependent on the operators degree of finesse and material being cut...

--
Leon Fisk
Grand Rapids MI

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/11/2023 10:55 AM, bob prohaska wrote:

I'd like to machine a few (2 or 3) teflon gasket rings out of quarter
inch sheet stock. The ID needs to be roughly 50 mm, the OD about 60 mm
and thickness that of the stock. The only critical dimension is the OD,
which has to be a snug fit in the groove where it'll live.

The sheet stock is what I happen to have. Likely most people would start
with bar stock then turn, bore and part off.

It's been a couple decades since I last did this, and all I can remember was that fixturing was a bit of a pain. I think I turned the OD first, with the stock pinched between chuck jaw tips and tailstock, but I can't remember how I held the resulting disk to bore the ID. It's way too soft to hold in a chuck.

Everything I can think of involves making at least one faceplace fixture and probably two. Can anybody point me to simpler methods? I'm not looking to save
time so much as material; I'm retired, so time is cheap but it looks like any reasonable teflon stock will cost at least $100. And, it's good mental exercise.

Thanks for reading,

bob prohaska

I haven't seen anyone suggest this . If you can cut an accurate
center hole in the material (maybe screw a square piece to a wood block
held in your chuck) , machine a mandrel with a stub a half inch long
sized to fit that hole just snug and a cup that fits over the stub that
will clamp your gasket ring in place . Cut your center hole , clamp the
piece to the stub mandrel with the cup and tailstock ram , machine the OD .
--
Snag
Men don't protect women because they're weak .
We protect them because they're important .

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/11/2023 9:55 AM, bob prohaska wrote:

I'd like to machine a few (2 or 3) teflon gasket rings out of quarter
inch sheet stock. The ID needs to be roughly 50 mm, the OD about 60 mm
and thickness that of the stock. The only critical dimension is the OD,
which has to be a snug fit in the groove where it'll live.

The sheet stock is what I happen to have. Likely most people would start
with bar stock then turn, bore and part off.

It's been a couple decades since I last did this, and all I can remember was that fixturing was a bit of a pain. I think I turned the OD first, with the stock pinched between chuck jaw tips and tailstock, but I can't remember how I held the resulting disk to bore the ID. It's way too soft to hold in a chuck.

Everything I can think of involves making at least one faceplace fixture and probably two. Can anybody point me to simpler methods? I'm not looking to save
time so much as material; I'm retired, so time is cheap but it looks like any reasonable teflon stock will cost at least $100. And, it's good mental exercise.

Thanks for reading,

bob prohaska

Wait. Are you the one that doesn't have machine tools like a mill or
lathe? Might be able to use a drill press, or even a hand held drill
motor, and bring it in a little at a time.

If this is the gasket for a compressor check valve, it might be that the
front and back faces are the sealing surfaces. I've used PTFE to make a
check valve gasket before, but it didn't last long for me. Maybe I did
a bad job, but the gasket wasn't the only thing flaky with it.


--
Bob La Londe
CNC Molds N Stuff


--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Bob La Londe <none@none.com99> wrote:

Wait. Are you the one that doesn't have machine tools like a mill or
lathe?

No mill or drill press. I do have a lathe, old South Bend 10k and
some limited tooling (3&4 jaw chucks, drill chuck for tailstock,
faceplates, boring tools, bits and random small extras like a steadyrest.
Oh, and a pedestal grinder the shaping bits.

Might be able to use a drill press, or even a hand held drill
motor, and bring it in a little at a time.

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

If this is the gasket for a compressor check valve, it might be that the front and back faces are the sealing surfaces. I've used PTFE to make a check valve gasket before, but it didn't last long for me. Maybe I did
a bad job, but the gasket wasn't the only thing flaky with it.

This is a group gasket for an old espresso machine, an Olympia Maximatic.
It seals on the faces, or one face and the OD depending on how tight it
fits in the groove. The face that seals against the basket needs to be flat. For that reason a molded o-ring isn't satisfactory (I tried it).

The dimensions are rather odd. The groove ID is very close to 1.875", but
the OD is 2.293", which isn't anything I recognize as a common size.
The depth is about 5 mm, but the gasket normally sticks out another two
or 3 mm, there's quite a bit of freedom. I've been using a thin o-ring
to shim the gasket thickness, and that's worked surprisingly well. The
first gasket of this type that I made lasted close to twenty years, thus
my lack of recall in how I made it.

Thanks for reading and replying!

bob prohaska

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/12/2023 7:38 AM, Jim Wilkins wrote:

"Snag"  wrote in message news:ul8p8p$3hs8o$1@dont-email.me...

  I haven't seen anyone suggest this . If you can cut an accurate
center  hole in the material (maybe screw a square piece to a wood block held in your chuck) , machine a mandrel with a stub a half inch long
sized to fit that hole just snug and a cup that fits over the stub that
will clamp your gasket ring in place . Cut your center hole , clamp the
piece to the stub mandrel with the cup and tailstock ram , machine the OD . Snag

------------------------
Searching in the shed I found a 1-1/2" PVC pipe cap which has an ID of
about 48mm and OD about 57mm.

Robert's your mother's brother ... so all he has to do is machine the
stub arbor .
--
Snag
Men don't protect women because they're weak .
We protect them because they're important .

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tue, 12 Dec 2023 19:54:22 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Bob La Londe <none@none.com99> wrote:

Wait. Are you the one that doesn't have machine tools like a mill or
lathe?

No mill or drill press. I do have a lathe, old South Bend 10k and
some limited tooling (3&4 jaw chucks, drill chuck for tailstock,
faceplates, boring tools, bits and random small extras like a steadyrest.
Oh, and a pedestal grinder the shaping bits.

Might be able to use a drill press, or even a hand held drill
motor, and bring it in a little at a time.

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

If this is the gasket for a compressor check valve, it might be that the
front and back faces are the sealing surfaces. I've used PTFE to make a
check valve gasket before, but it didn't last long for me. Maybe I did
a bad job, but the gasket wasn't the only thing flaky with it.

This is a group gasket for an old espresso machine, an Olympia Maximatic.
It seals on the faces, or one face and the OD depending on how tight it
fits in the groove. The face that seals against the basket needs to be flat. >For that reason a molded o-ring isn't satisfactory (I tried it).

The dimensions are rather odd. The groove ID is very close to 1.875", but
the OD is 2.293", which isn't anything I recognize as a common size.
The depth is about 5 mm, but the gasket normally sticks out another two
or 3 mm, there's quite a bit of freedom. I've been using a thin o-ring
to shim the gasket thickness, and that's worked surprisingly well. The
first gasket of this type that I made lasted close to twenty years, thus
my lack of recall in how I made it.

I'd be tempted to make the arbor section that the O-ring ID rests on
slightly undersize and machine the O-ring OD to the claimed dimension,
using a very sharp HSS cutting bit. Finding the right angle may
require some experimentation.

Then, when the new O-ring is installed, the ID part will force the
ring to expand against the OD component, sealing it.

This may be helpful:

.<https://www.quandaplastic.com/brief-introduction-of-turning-processing-method-of-teflon-ptfe-film/#:~:text=The%20cutting%20edge%20should%20be,be%2020%20~30%C2%B0%20above.>

Joe Gwinn

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/12/2023 1:54 PM, bob prohaska wrote:

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

bob prohaska

Mount a wood block in your 4 jaw chuck (and face it off) . Tack or
screw a square piece of your material to the wood block . Machine the ID
. See my other posts in this thread to proceed from there .
--
Snag
Men don't protect women because they're weak .
We protect them because they're important .

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/12/2023 3:19 PM, Snag wrote:

On 12/12/2023 1:54 PM, bob prohaska wrote:

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

bob prohaska

  Mount a wood block in your 4 jaw chuck (and face it off) . Tack or
screw a square piece of your material to the wood block . Machine the ID
. See my other posts in this thread to proceed from there .

Wood block with a fender washer or similar large cap would work for
turning the outside. Then a large ring on the outside with screws, and
trepan and/or bore the ID.


--
Bob La Londe
CNC Molds N Stuff


--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/12/2023 23:48, Jim Wilkins wrote:

"bob prohaska"  wrote in message news:uladpe$3pjus$1@dont-email.me...

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

-------------------------

The proper chuck is a "pot collet" bored slightly larger than the work
OD with pins or shims in the slots to hold it open. When tightened the
collet clamps the work in place with full support all around.

This shows one with the chucked work being indicated, and empty, and
also compares and gives advantages of 5C vs ER such as square and hex collets, which I have and use. https://thecogwheel.net/2018/04/16/5c-collet-chuck/

I totally agree with the comments there regarding pros and cons of 5C
and ER collets as I have both and have encountered some of those
limitations. For short items I have some 5C emergency collets machined
to suit and they work great except the Chinese makers substituted the
wrong sized pins, like 3.5mm instead of 1/8" but drilled the holes to
1/8" near enough. For the collet chuck I had considered buying a Bison
of that style which in my experience would have been top notch kit but
went for the Kalamazoo. I watched this video the other day about such 5C closers https://www.youtube.com/watch?v=jQ3JutSejU4 and very little
runout but not built to last, but in the comments indications that other similar 5C closers are better made at not that much extra price,
research required.

This is the new URL for Metal Lathe Accessories, the collet chuck is
MLA-21.
https://www.metallatheaccessories.com/

Interesting to look at the accessories, one of my favourite  mods to my
lathe in recent years was to acquire a 2nd tailstock and modify it for
lever operation which I find I prefer for what I do over the standard
screw feed tailstock.

The quick and dirty substitute is the wooden cup chuck I mentioned. If
you need to turn only the ID and not the face of the ring it can be
clamped with screws and washers.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Jim Wilkins <muratlanne@gmail.com> wrote:

"bob prohaska" wrote in message news:uladpe$3pjus$1@dont-email.me...

My problem (at least the one I recognize) is holding the workpiece
while finishing the ID. No problem making it spin 8-)

-------------------------

The proper chuck is a "pot collet" bored slightly larger than the work OD with pins or shims in the slots to hold it open. When tightened the collet clamps the work in place with full support all around.

After some rumination, I think the original sequence of operations was
1. Hold the work blank by the outside scrap, finish the ID
2. Center the work by the ID, hold it by the face and finish the OD.

Initially I didn't like that sequence, because it required two accurate operations of which only the second mattered, doubling the risk of error.

Looking at the tooling required for my preferred sequence, the original
method looks a bit simpler for only three parts. The idea of using pipe
caps for mandrels never crossed my mind and seems a good idea. They
can be run between centers, making them reproducible.

This shows one with the chucked work being indicated, and empty, and also compares and gives advantages of 5C vs ER such as square and hex collets, which I have and use.
https://thecogwheel.net/2018/04/16/5c-collet-chuck/

This is the new URL for Metal Lathe Accessories, the collet chuck is MLA-21. https://www.metallatheaccessories.com/

Alas, my lathe uses 6k collets 8-(

Those are interesting links, thanks for posting!

Thanks to everyone!

bob prohaska

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 14/12/2023 14:21, Jim Wilkins wrote:

"David Billington"  wrote in message news:ulb6kd$rmg$1@dont-email.me...
I totally agree with the comments there regarding pros and cons of 5C
and ER collets as I have both and have encountered some of those
limitations.
----------------------

What do you think of this, which puts ER collets on a 5C indexer? https://www.amazon.com/Accusize-Tools-Shank-Collet-0223-0302/dp/B07CT53WMC

That looks like it might come in handy as I have a 5C indexer and a full
set of ER40 metric collets, my 5C collet set only contains some common
metric and inch round sizes acquired as needed or some common sizes to
have on hand just in case. I have a 5C 3 jaw self centring chuck for
dealing with hex stock. The ER40 full set was bought later and now sees
more use than the 5C and I have an ER40 square and hex block for 3,4,
and 6 but I can see the temptation to treat myself to one of those in
time for Christmas. Thanks for the heads up.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Here's a YouTube video of an alternative holding scheme for thin rings:

https://www.youtube.com/watch?v=7g_GtSpo5-A

It relies on a three jaw chuck for clamping a simple right
circular cylinder collet with a single split. Wish I'd seen
it sooner.

It's not clear I could have used it, as my three jaw chuck
didn't come with reversible jaws, but I'm still slightly
embarrassed that nothing like it ever crossed my mind.

Thanks for reading,

bob prohaska

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)