The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree, but
I'm not the machinist - I just draw the pretty pictures) is too wide and
the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich

In article ,
Rich Grise wrote:

The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree, but
I'm not the machinist - I just draw the pretty pictures) is too wide and
the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich

Well, this is the cheat sheet I've been using for decades for inch-sized
o-rings on vacuum systems. Since it clearly doesn't match any of what
you posted, perhaps our inch-sized o-rings were really the size they
claimed to be...

Anyway, you don't need (or want) to confine the ring 4 ways. You need
the ring to squish and seal (in the "depth" dimension), and you need to
give it room to squish (in the "width" dimension.)

All measurements are in inches. Measurements in brackets [] are -0.000,
my preferred end of the scale on these.
1/16"
width .085 + or - .003 [.082 +.006]
depth .052 + or - .002 [.050 +.004]
3/32"
width .120 + or - .003 [.117 +.006]
depth .077 + or - .003 [.074 +.006]
1/8"
width .160 + or - .003 [.157 +.006]
depth .104 + or - .003 [.101 +.006]
1/4"
width .325 + or - .003 [.322 +.006]
depth .206 + or - .005 [.201 +.010]

--
Cats, coffee, chocolate...vices to live by

"Rich Grise" wrote in message
...
The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland
depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree, but
I'm not the machinist - I just draw the pretty pictures) is too wide and
the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich


Roughly speaking, the o-ring will increase in width by the inverse of the
fraction it is compressed. In other words if it is compressed by a factor
of 0.8, the width will expand by a factor of 1.25 .

In your case the maximum diameter is .281 and the minimum compressed height
is .226, So the maximum width is .281(.281/.226) = .349 so a groove of
..375 makes sense.

On Tue, 18 Jan 2011 12:30:02 -0800, Rich Grise
wrote:

The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree, but
I'm not the machinist - I just draw the pretty pictures) is too wide and
the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich

You're not working at TCFNA Morton-Thiokol are you?

I think the number is about right. The O-ring squishes out sideways,
and you have to consider the tolerances of all dimensions and the
O-ring itself. A maximum size O-ring has to fit a minimum size groove
and gap.

Not much bad will happen if the groove is a bit wider than required
for the particular O-ring, but bad things will happen if the depth is
out of tolerance or the groove is too narrow.

Here's another source with exactly the same numbers for radial squeeze
applications (see page 9). Smaller numbers for axial and smaller again
for vacuum axial.

http://o-ring.info/en/technical%20ma...nformation.pdf

Spehro Pefhany wrote:
You're not working at TCFNA Morton-Thiokol are you?

You wouldn't happen to know anything about a frozen o-ring back in the early
80's , would you ?
I'm pretty sure I was involved with the standardization mixes for the
propellant on that one ...
And I know for sure I was on the crew that poured STS1A and 1B .
--
Snag
Learning keeps
you young !

Ecnerwal wrote:

In article ,
Rich Grise wrote:

The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland
depth (dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree,
but I'm not the machinist - I just draw the pretty pictures) is too wide
and the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich

Well, this is the cheat sheet I've been using for decades for inch-sized
o-rings on vacuum systems. Since it clearly doesn't match any of what
you posted, perhaps our inch-sized o-rings were really the size they
claimed to be...

Anyway, you don't need (or want) to confine the ring 4 ways. You need
the ring to squish and seal (in the "depth" dimension), and you need to
give it room to squish (in the "width" dimension.)

All measurements are in inches. Measurements in brackets [] are -0.000,
my preferred end of the scale on these.
1/16"
width .085 + or - .003 [.082 +.006]
depth .052 + or - .002 [.050 +.004]
3/32"
width .120 + or - .003 [.117 +.006]
depth .077 + or - .003 [.074 +.006]
1/8"
width .160 + or - .003 [.157 +.006]
depth .104 + or - .003 [.101 +.006]
1/4"
width .325 + or - .003 [.322 +.006]
depth .206 + or - .005 [.201 +.010]

Thanks!
Rich

Spehro Pefhany wrote:


http://o-ring.info/en/technical%20ma...nformation.pdf

Thanks!
Rich

anorton wrote:


"Rich Grise" wrote in message
...
The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland
depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree,
but I'm not the machinist - I just draw the pretty pictures) is too wide
and the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich


Roughly speaking, the o-ring will increase in width by the inverse of the
fraction it is compressed. In other words if it is compressed by a factor
of 0.8, the width will expand by a factor of 1.25 .

In your case the maximum diameter is .281 and the minimum compressed
height
is .226, So the maximum width is .281(.281/.226) = .349 so a groove of
.375 makes sense.

Thanks!
Rich

Rich Grise wrote:

Got my answer, so I guess we can retire the thread.

Thanks again to all!
Rich

"Ecnerwal" wrote in message
...
In article ,
Rich Grise wrote:

The machinist called me over and asked me to help him design an o-ring
groove. We looked up a chart at
http://www.parker.com/literature/ORD...g_Handbook.pdf

and on page 89 of the above PDF, there's a chart: Design guide 4-2.

It's clear that for nominal 1/4" (actual width .275 ± .006) the gland
depth
(dim. L) is .226-.229.

But on the chart, it seems to indicate that the groove width, G, for a
nominal 1/4 width, is .375-.380, which he thinks (and I tend to agree,
but
I'm not the machinist - I just draw the pretty pictures) is too wide and
the o-ring would flop around or something. He thinks the groove width
should come from the line above, and be .281-.286.

Anyone got the definitive answer for that?

Thanks 10E9 in advance!
Rich

Well, this is the cheat sheet I've been using for decades for inch-sized
o-rings on vacuum systems. Since it clearly doesn't match any of what
you posted, perhaps our inch-sized o-rings were really the size they
claimed to be...

Anyway, you don't need (or want) to confine the ring 4 ways. You need
the ring to squish and seal (in the "depth" dimension), and you need to
give it room to squish (in the "width" dimension.)

All measurements are in inches. Measurements in brackets [] are -0.000,
my preferred end of the scale on these.
1/16"
width .085 + or - .003 [.082 +.006]
depth .052 + or - .002 [.050 +.004]
3/32"
width .120 + or - .003 [.117 +.006]
depth .077 + or - .003 [.074 +.006]
1/8"
width .160 + or - .003 [.157 +.006]
depth .104 + or - .003 [.101 +.006]
1/4"
width .325 + or - .003 [.322 +.006]
depth .206 + or - .005 [.201 +.010]

--
Cats, coffee, chocolate...vices to live by

PURE GOLD! Thanks, I wish I had this years ago!