All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric

On Thursday, April 16, 2015 at 11:00:16 AM UTC-7, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool ...
... to find out what radii to grind the sides of the tool
can be determined by drawing the screw head...directly measure with the cad
program

Dude, coffee isn't enough, you need sleep.
To seat an o-ring, you get the groove dimensions from the manufacturer of
the o-ring.
And to seal a 304 stainless screw head, a soft copper gasket makes more sense.

On Thu, 16 Apr 2015 12:44:38 -0700 (PDT), whit3rd
wrote:

On Thursday, April 16, 2015 at 11:00:16 AM UTC-7, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool ...
... to find out what radii to grind the sides of the tool
can be determined by drawing the screw head...directly measure with the cad
program

Dude, coffee isn't enough, you need sleep.
To seat an o-ring, you get the groove dimensions from the manufacturer of
the o-ring.
And to seal a 304 stainless screw head, a soft copper gasket makes more sense.
I guess I wasn't clear in my first post. The o-ring groove is going
into an angled face and the groove is normal to that face.
The customer wants an o-ring. We discussed this. The screw bears
against aluminum. And his customer needs to be able to replace the
o-ring at will. Soft copper washers are not as near as common as
o-rings.
Eric

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric

On Thu, 16 Apr 2015 13:25:17 -0700, wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric
I know, I know, replying to a post that is a reply to my own post is
really bad form. Makes me look weird, like jon banquer. Anyway, after
looking at the groove drawing I know I am correct. But please feel
free to correct me if I am wrong. And don't tell banquer that I am
replying to my own posts, he might think I'm like him.
Eric

On Thursday, April 16, 2015 at 1:18:27 PM UTC-7, wrote:
On Thu, 16 Apr 2015 12:44:38 -0700 (PDT), whit3rd
wrote:

On Thursday, April 16, 2015 at 11:00:16 AM UTC-7, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool ...

To seat an o-ring, you get the groove dimensions from the manufacturer of
the o-ring.
And to seal a 304 stainless screw head, a soft copper gasket makes more sense.

I guess I wasn't clear in my first post. The o-ring groove is going
into an angled face and the groove is normal to that face.
The customer wants an o-ring. We discussed this. The screw bears
against aluminum.

I wouldn't do it the hard way, with a groove in the head. I'd make a square
tool cut in the head, and another (end-mill) square cut in the seat,
to make the correct size 'box' for the as-compressed O-ring.
It might be best to use an O-ring that seals against its inner and outer
circumference, those are the easiest dimensions to control.

Holding the screw while making the cut can be ... challenging. Maybe
you'll be threading a soft collet?

"whit3rd" wrote in message
...
On Thursday, April 16, 2015 at 11:00:16 AM UTC-7,
wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool ...
... to find out what radii to grind the sides of the tool
can be determined by drawing the screw head...directly measure with
the cad
program

Dude, coffee isn't enough, you need sleep.
To seat an o-ring, you get the groove dimensions from the
manufacturer of
the o-ring.
And to seal a 304 stainless screw head, a soft copper gasket makes
more sense.

Figure 5 shows how O-rings seal hydraulic fittings.
http://www.webtec.com/en/tech/connections

-jsw

On Thu, 16 Apr 2015 14:00:53 -0700 (PDT), whit3rd
wrote:

On Thursday, April 16, 2015 at 1:18:27 PM UTC-7, wrote:
On Thu, 16 Apr 2015 12:44:38 -0700 (PDT), whit3rd
wrote:

On Thursday, April 16, 2015 at 11:00:16 AM UTC-7, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool ...

To seat an o-ring, you get the groove dimensions from the manufacturer of
the o-ring.
And to seal a 304 stainless screw head, a soft copper gasket makes more sense.

I guess I wasn't clear in my first post. The o-ring groove is going
into an angled face and the groove is normal to that face.
The customer wants an o-ring. We discussed this. The screw bears
against aluminum.

I wouldn't do it the hard way, with a groove in the head. I'd make a square
tool cut in the head, and another (end-mill) square cut in the seat,
to make the correct size 'box' for the as-compressed O-ring.
It might be best to use an O-ring that seals against its inner and outer
circumference, those are the easiest dimensions to control.

Holding the screw while making the cut can be ... challenging. Maybe
you'll be threading a soft collet?
I need to make these for about 25 cents each in quantities of 500. I
can do that with only cutting a groove in the lathe. I can't cut the
seats econimically. Besides, cutting a groove normal to the angled
face is an accepted way of using O-rings, I have done it before, just
not on the underside of the part. I am not sure if I will be using a
soft collet. I may end up having to face the whole underside of the
screw head, but I really want to avoid that because of accelerated
tool wear and I don't want to use two tools. I may be able to come up
with a horseshoe shaped device that lets me locate off the angled
surface and then I remove the device and press start. I will most
likely use a dead length collet closer in the lathe.
Eric

On Thu, 16 Apr 2015 13:29:50 -0700, etpm wrote:

On Thu, 16 Apr 2015 13:25:17 -0700, wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool once.
So I think to find out what radii to grind the sides of the tool can be
determined by drawing the screw head with the groove in it. Then extend
the sides of the head until they meet. Then mirror the drawing around
that point. Then I can directly measure with the cad program the two
different radii of the sides of the groove. Am I correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and is
normal to that surface, not to either the axis of the screw or the top
face of the screw. I alread know I need a 5/16" dia o-ring. But since
the groove is normal to the angled face the sides of the groove will
have larger radii than the radius of 5/16".
Eric
I know, I know, replying to a post that is a reply to my own post is
really bad form. Makes me look weird, like jon banquer. Anyway, after
looking at the groove drawing I know I am correct. But please feel free
to correct me if I am wrong. And don't tell banquer that I am replying
to my own posts, he might think I'm like him.
Eric

Here, let me break up your string of self-replies (I don't know if you
resemble Jon or not -- I've had him plonked for years).

Man, this is so damned confusing. Can you post a picture someplace? So
you're making a grove in the angled part of a flathead screw, so you can
slap an O-ring on there and seal to aluminum -- yes?

And the grove will go in normal to the face, which means that as the
groove gets deeper, the radius of the grove gets smaller -- yes?

And you want to make a tool with JUST ONE TRY, to make it all work -- yes?

Dayum -- you're a brave man.

Why can't you just turn a straight section in the screw head, a hair
larger in diameter than the ID of the O-ring, and just the right depth to
accommodate the thing when the screw is tightened? Then you can just use
a standard insert. It'll look like a shoulder on the screw head. Unless
you have some compelling reason for the screw head to capture the O-ring
(and **** off anyone trying to get one out without damaging it), wouldn't
this meet your stated goals?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section? Grooves
are usually rectangular to allow the o-ring to squish in compression.

"Bob Engelhardt" wrote in message
...
On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved.
I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the
tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section?
Grooves are usually rectangular to allow the o-ring to squish in
compression.

I think he's trying to translate the theoretically conical circular
relief below the outer cutting edge into a cylindrical relief he can
more easily grind.

-jsw

On Thu, 16 Apr 2015 20:50:32 -0400, "Jim Wilkins"
wrote:


"Bob Engelhardt" wrote in message
...
On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved.
I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the
tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section?
Grooves are usually rectangular to allow the o-ring to squish in
compression.

I think he's trying to translate the theoretically conical circular
relief below the outer cutting edge into a cylindrical relief he can
more easily grind.

-jsw

I haven't tried very hard to follow all of this, but is he talking
about grinding a circular or conical side relief on the tool? Because
face-grooving tools typically are ground with a straight relief all
around.

Unless he really can exploit some extremely small advantage by making
the reliefs as compliant to the grooved shape as possible, there
doesn't seem to be much of an advantage to making it so complicated.

Or maybe I'm missing the point -- no pun intended.

--
Ed Huntress

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric

Firstly, you don't need to use carbide to machine 304, you can do it
with hi-speed tooling. Just slow the cutting speed down.
--
Cheers,

John B.

Jim Wilkins wrote:
"Bob Engelhardt" wrote in message
...
On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved.
I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the
tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section?
Grooves are usually rectangular to allow the o-ring to squish in
compression.

I think he's trying to translate the theoretically conical circular
relief below the outer cutting edge into a cylindrical relief he can
more easily grind.

-jsw

That's what I thought too . Like clearancing the trailing edge of trepanning
cutter , but for a cone . IMO the easiest way to do this cut is with the
compound angled to let you feed the cutter perpendicular to the underside of
the screw head . If you're careful grinding that tool , the cutter can
deburr the cut just as it comes to depth .

--
Snag

wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric

ACME thread cutting insert?

--
Steve W.

On Thu, 16 Apr 2015 12:44:38 -0700 (PDT), whit3rd
wrote:

On Thursday, April 16, 2015 at 11:00:16 AM UTC-7, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool ...
... to find out what radii to grind the sides of the tool
can be determined by drawing the screw head...directly measure with the cad
program

Dude, coffee isn't enough, you need sleep.
To seat an o-ring, you get the groove dimensions from the manufacturer of
the o-ring.

Ayup.

And to seal a 304 stainless screw head, a soft copper gasket makes more sense.

Ayup again.


"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke

On Thursday, April 16, 2015 at 2:59:21 PM UTC-7, Jim Wilkins wrote:
"whit3rd" wrote in message
...
On Thursday, April 16, 2015 at 11:00:16 AM UTC-7,
wrote:

I need to put an o-ring groove in the underside of 500 1/4-20
flathead screws. So I need to make a groove tool ...
... what radii to grind the sides of the tool

[recommend shoulder cut and seat cut to make square-section
toroidal space for O-ring]

Figure 5 shows how O-rings seal hydraulic fittings.
http://www.webtec.com/en/tech/connections

Yes, that illustrates the alternative perfectly.

As for cutting the aluminum seat, a piloted counterbore, with a stop, could be
chucked in a hand drill; this size of counterbore might be a standard item.
Clearing the chips, though, might be a problem.

Making soft jaws, or machining a soft collet, to hold the screw
by the head, seems advisable. That way, if something slips, it
doesn't ruin the cut (and flex of the workpiece is lower)

If one wants to do a square groove with sidewalls perpendicular to the
cone screwhead, the 'radius' of minimum clearance is the radius of
the deepest penetration of the upslope (shallowest) corner (and the axis is
the rotation axis of the spindle). It's a bit tricky.

"whit3rd" wrote in message
...
On Thursday, April 16, 2015 at 2:59:21 PM UTC-7, Jim Wilkins wrote:
"whit3rd" wrote in message
...
On Thursday, April 16, 2015 at 11:00:16 AM UTC-7,

wrote:

I need to put an o-ring groove in the underside of 500 1/4-20
flathead screws. So I need to make a groove tool ...
... what radii to grind the sides of the tool

[recommend shoulder cut and seat cut to make square-section
toroidal space for O-ring]

Figure 5 shows how O-rings seal hydraulic fittings.
http://www.webtec.com/en/tech/connections

Yes, that illustrates the alternative perfectly.

As for cutting the aluminum seat, a piloted counterbore, with a
stop, could be
chucked in a hand drill; this size of counterbore might be a
standard item.
Clearing the chips, though, might be a problem.

Making soft jaws, or machining a soft collet, to hold the screw
by the head, seems advisable. That way, if something slips, it
doesn't ruin the cut (and flex of the workpiece is lower)

If one wants to do a square groove with sidewalls perpendicular to
the
cone screwhead, the 'radius' of minimum clearance is the radius of
the deepest penetration of the upslope (shallowest) corner (and the
axis is
the rotation axis of the spindle). It's a bit tricky.

The ID at the groove's bottom has the tightest radius but it curves
away from the cutting tool. The OD at the bottom had an effective
radius larger than it would be for a cylindrical groove because of the
angle.

If the groove were in a flat face the clearance would be the same as
the groove radius, but as the angle tightens the necessary outer
clearance radius increases, becoming very large as the cone approaches
cylindrical and then infinite, a straight line like a parting tool. I
didn't learn the trigonometry of conic sections to calculate this, the
ellipse generated by a plane cutting a cone at an angle.
http://en.wikipedia.org/wiki/Conic_section

I think this means grinding for 5/16" would work but I'd make a
quickie test bit from HSS to check this, and also that the O ring
seals, stays in and can be replaced.

What's the maximum clearance angle a carbide bit can have without
being too weak? I just use 5 degrees of surface-ground flat clearance
for everything, leaving enough to support the edge and freehand
grinding boring and grooving bits to more than enough circular relief
below that. Perhaps a small carbide boring bit could be ground narrow
enough on the ID side which needs only flat clearance?

-jsw

wrote:
On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric


I think its a poor idea to make a round groove normal
to the surface. A square cut like the crude profile drawing
below will perform better. O-rings are not all that precise.
cutting a groove that tries to match the shape of the o-ring
invites trouble and won't work better than a square groove.

_______
_/
|
/
|
|
|

On Fri, 17 Apr 2015 08:53:27 -0500, jim "
wrote:

wrote:
On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric


I think its a poor idea to make a round groove normal
to the surface. A square cut like the crude profile drawing
below will perform better. O-rings are not all that precise.
cutting a groove that tries to match the shape of the o-ring
invites trouble and won't work better than a square groove.


When O-rings are under pressure, a possible key to shaping the grooves
is the way the pressure will be applied. In the job shop I worked in,
we made ball-and-socket fittings for electron-beam guns that were used
in vacuum chambers, and the O-ring grooves had to be a tapered wedge,
from one side to the other. The vacuum sucked the O-ring into the
shallower side of the wedge.

--
Ed Huntress

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:


I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws.
snip
Might be overkill. What sort of pressures are involved?
What are you sealing? Was a flat rubber/elastomer
(urethane?) washer evaluated? How about a combination seal
and retaining compound like RTV or Loctite?

If the O-ring groove is mandatory, how about a hollow mill?
with the correct geometry? Given the problems in holding/
handling you might be better off making the complete screw
from bar stock, although slotting the head may be a
challenge. Do you have a CNC with a bar puller? How long is
the thread? Style of head/drive?




--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn

On Thu, 16 Apr 2015 19:24:27 -0500, Tim Wescott
wrote:

On Thu, 16 Apr 2015 13:29:50 -0700, etpm wrote:

On Thu, 16 Apr 2015 13:25:17 -0700, wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool once.
So I think to find out what radii to grind the sides of the tool can be
determined by drawing the screw head with the groove in it. Then extend
the sides of the head until they meet. Then mirror the drawing around
that point. Then I can directly measure with the cad program the two
different radii of the sides of the groove. Am I correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and is
normal to that surface, not to either the axis of the screw or the top
face of the screw. I alread know I need a 5/16" dia o-ring. But since
the groove is normal to the angled face the sides of the groove will
have larger radii than the radius of 5/16".
Eric
I know, I know, replying to a post that is a reply to my own post is
really bad form. Makes me look weird, like jon banquer. Anyway, after
looking at the groove drawing I know I am correct. But please feel free
to correct me if I am wrong. And don't tell banquer that I am replying
to my own posts, he might think I'm like him.
Eric

Here, let me break up your string of self-replies (I don't know if you
resemble Jon or not -- I've had him plonked for years).

Man, this is so damned confusing. Can you post a picture someplace? So
you're making a grove in the angled part of a flathead screw, so you can
slap an O-ring on there and seal to aluminum -- yes?

And the grove will go in normal to the face, which means that as the
groove gets deeper, the radius of the grove gets smaller -- yes?

And you want to make a tool with JUST ONE TRY, to make it all work -- yes?

Dayum -- you're a brave man.

Why can't you just turn a straight section in the screw head, a hair
larger in diameter than the ID of the O-ring, and just the right depth to
accommodate the thing when the screw is tightened? Then you can just use
a standard insert. It'll look like a shoulder on the screw head. Unless
you have some compelling reason for the screw head to capture the O-ring
(and **** off anyone trying to get one out without damaging it), wouldn't
this meet your stated goals?
The customer wants the O-ring to seat high up the taper. He wants the
groove normal to the angled surface. I think though that I may be able
to talk him into a groove that is normal to the screw axis.
Eric

On Fri, 17 Apr 2015 09:58:38 -0400, Ed Huntress
wrote:

On Fri, 17 Apr 2015 08:53:27 -0500, jim "
wrote:

wrote:
On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric


I think its a poor idea to make a round groove normal
to the surface. A square cut like the crude profile drawing
below will perform better. O-rings are not all that precise.
cutting a groove that tries to match the shape of the o-ring
invites trouble and won't work better than a square groove.


When O-rings are under pressure, a possible key to shaping the grooves
is the way the pressure will be applied. In the job shop I worked in,
we made ball-and-socket fittings for electron-beam guns that were used
in vacuum chambers, and the O-ring grooves had to be a tapered wedge,
from one side to the other. The vacuum sucked the O-ring into the
shallower side of the wedge.
The o-ring will be sealing against low pressure-basically water a few
inches deep. So the sealing cannot be helped by pressure or vacuum and
instead must rely solely on compression. The customer would rather use
stock o-rings that are available everywhere.
Eric

On Thu, 16 Apr 2015 20:35:10 -0400, Bob Engelhardt
wrote:

On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section? Grooves
are usually rectangular to allow the o-ring to squish in compression.
The groove is square cross section.

On Thu, 16 Apr 2015 20:54:59 -0400, Ed Huntress
wrote:

On Thu, 16 Apr 2015 20:50:32 -0400, "Jim Wilkins"
wrote:


"Bob Engelhardt" wrote in message
...
On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved.
I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the
tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section?
Grooves are usually rectangular to allow the o-ring to squish in
compression.

I think he's trying to translate the theoretically conical circular
relief below the outer cutting edge into a cylindrical relief he can
more easily grind.

-jsw

I haven't tried very hard to follow all of this, but is he talking
about grinding a circular or conical side relief on the tool? Because
face-grooving tools typically are ground with a straight relief all
around.

Unless he really can exploit some extremely small advantage by making
the reliefs as compliant to the grooved shape as possible, there
doesn't seem to be much of an advantage to making it so complicated.

Or maybe I'm missing the point -- no pun intended.
Greetings Ed,
The tool is only .06 wide and the groove radius is small so I need
circular contours for strength. Remember, I have made tools like this
before just because of the needed strength.
Eric

On Fri, 17 Apr 2015 07:57:21 +0700, John B. Slocomb
wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric

Firstly, you don't need to use carbide to machine 304, you can do it
with hi-speed tooling. Just slow the cutting speed down.
Greetings John,
I know I can use HSS. I need to do 500 of these at a time and need to
do them fast.
Eric

On Fri, 17 Apr 2015 09:30:48 -0500, F. George McDuffee
wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:


I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws.
snip
Might be overkill. What sort of pressures are involved?
What are you sealing? Was a flat rubber/elastomer
(urethane?) washer evaluated? How about a combination seal
and retaining compound like RTV or Loctite?

If the O-ring groove is mandatory, how about a hollow mill?
with the correct geometry? Given the problems in holding/
handling you might be better off making the complete screw
from bar stock, although slotting the head may be a
challenge. Do you have a CNC with a bar puller? How long is
the thread? Style of head/drive?
Greetings George,
I already know how to hold and locate the screw. It will take
approximately 4 seconds to remove one screw and put another in the
collet. What I really want to know is if my way of finding the radii
of the walls of the groove is one correct way.
Eric

On Fri, 17 Apr 2015 10:40:37 -0400, Joe Gwinn
wrote:

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn
Greetings Joe,
Zago does indeed sell those screws. $2.90 each in quantity. I need to
be able to make these for about 25 cents. And I will. Thinbit does not
make the groove tool I need. They will though, for about &175.00. I
have been through this before.
Eric

On Fri, 17 Apr 2015 09:24:09 -0700, wrote:

snip
The o-ring will be sealing against low pressure-basically water a few
inches deep. So the sealing cannot be helped by pressure or vacuum and
instead must rely solely on compression. The customer would rather use
stock o-rings that are available everywhere.
/snip
o-ring is overkill -- use flat rubber washer for face
compression seal.


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"

wrote in message ...

On Thu, 16 Apr 2015 20:35:10 -0400, Bob Engelhardt
wrote:

On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section? Grooves
are usually rectangular to allow the o-ring to squish in compression.
The groove is square cross section.
================================================== ============

I hope you meant rectangular, not square. The oring is deformable but not
compressible, so the cross-sectional area of the groove needs to be bigger
than the cross-sectional area of the oring else you extrude and cut it on
tightening. As for the geometry you could do it with a sketch and trig but
I would prefer to just draw it in a cad program. Being a lover of run-on
sentences here's how I would do it in autocad. Draw an angled line to
represent the angled side of the flat head, draw a line perpendicular to
that for the end of the oring groove closest to the threads, make an offset
copy of the first line offsetting by 80% (or 75% or whatever you choose from
the Parker oring handbook for your oring and pressure and oring life but it
almost always works out to be between 75 and 80%) to be the bottom of the
groove, draw a circle for the oring tangent to the side and bottom of the
groove, and finally an offset copy of the first side line offset by 125-150%
of the oring diameter to be the second side of the groove (this creates the
extra cross-sectional area for the oring to deform into, and isn't critical
so long as it is large enough). Draw a line parallel to the screw axis
offset from the center of the oring by the radius of the ring (which also be
the centerline axis of the screw), trim all the original groove lines to
just leave the rectangular groove, then reflect everything around the
centerline axis. Now add the top of the flat head and the threaded section,
trim the excess from the angled lines, and you can pick off the dimensions
you need. That's the stuff I'm sure off, the actual machining I'm less help
with. On a manual lathe the way to do this would be to use a tool with a
squared-off end like a parting tool and rotate the compound to the right
angle and just plunge the compound. On a cnc couldn't you grind the end of
a boring bar to the parting tool shape at the angle you need, and then make
the angled plunge cut to simulate the straight plunge of a compound link you
were turning a taper? Either way I don't see where you need any kind of a
radius on the cutting tool, except a tiny break on the two front corners to
leave a rounded chamfer at the bottom corners of the groove for stress
relief. Hope this helps some :-).

Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net

Ed Huntress wrote:
On Fri, 17 Apr 2015 08:53:27 -0500, jim "
wrote:

wrote:
On Thu, 16 Apr 2015 11:04:10 -0700, wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I know it's bad form to reply to your own post but I obviously need to
make a clarification. The groove is going into an angled surface and
is normal to that surface, not to either the axis of the screw or the
top face of the screw. I alread know I need a 5/16" dia o-ring. But
since the groove is normal to the angled face the sides of the groove
will have larger radii than the radius of 5/16".
Eric


I think its a poor idea to make a round groove normal
to the surface. A square cut like the crude profile drawing
below will perform better. O-rings are not all that precise.
cutting a groove that tries to match the shape of the o-ring
invites trouble and won't work better than a square groove.


When O-rings are under pressure, a possible key to shaping the grooves
is the way the pressure will be applied. In the job shop I worked in,
we made ball-and-socket fittings for electron-beam guns that were used
in vacuum chambers, and the O-ring grooves had to be a tapered wedge,
from one side to the other. The vacuum sucked the O-ring into the
shallower side of the wedge.


I'm assuming the screws are going to be tightened,
which means you can get much much more than enough
compression of the oring. The trick will be to
have the right amount of compression and
design it so it doesn't tear, cut into or shred
the oring when the screw is tightened all the way.

On Friday, April 17, 2015 at 12:50:11 PM UTC-4, wrote:
On Fri, 17 Apr 2015 10:40:37 -0400, Joe Gwinn
wrote:

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn
Greetings Joe,
Zago does indeed sell those screws. $2.90 each in quantity. I need to
be able to make these for about 25 cents. And I will. Thinbit does not
make the groove tool I need. They will though, for about &175.00. I
have been through this before.
Eric

Not for nothin', but it seems to me that for $125 total project income (500 pieces at $0.25 each), you're going to have a tough time making a profit on this. You've probably spent more than $125 worth of time just thinking about the tooling.

After 30+ years in business, I've learned that there are some jobs you just ought to walk away from. Tell the customer he can buy the parts for $2.90 from Zago.

Just sayin'

In article ,
wrote:

On Fri, 17 Apr 2015 10:40:37 -0400, Joe Gwinn
wrote:

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn
Greetings Joe,
Zago does indeed sell those screws. $2.90 each in quantity. I need to
be able to make these for about 25 cents. And I will. Thinbit does not
make the groove tool I need. They will though, for about &175.00. I
have been through this before.

I assume that Zago has competitors by now. Given competition and low
the production volume, this may be a good price.

One can mine thinbit's catalog for ideas. I've made face grooving
tools by grinding HSS. The hard part may be holding the screw to be
machined.

And, maybe the better approach is to have special screws made, complete
with groove, instead of trying to modify existing screws.* A Swiss
screw machine would make short work of this. The minimum order may be
10,000 screws.

Joe Gwinn

On 16/04/15 19:04, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric
I wonder if you could use a rotabroach type cutter as used in magnetic
drills, I have quite a few and they go down to 10mm hole size in metric,
maybe 3/8" in inch as that is close. The pilots are 1/4" IIRC so they
may be ideal if the end geometry is suitable and you can control the
depth. They are available in carbide but the only ones I've used are
HSS. I cut 304 with my HSS ones frequently and they go fine but I
haven't cut anywhere near 500 so couldn't comment on longevity. I
suspect a maker of the cutters could comment on the likely lifetime
before re-sharpening if required.

On Friday, April 17, 2015 at 3:00:29 PM UTC-4, rangerssuck wrote:
On Friday, April 17, 2015 at 12:50:11 PM UTC-4, wrote:
On Fri, 17 Apr 2015 10:40:37 -0400, Joe Gwinn
wrote:

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn
Greetings Joe,
Zago does indeed sell those screws. $2.90 each in quantity. I need to
be able to make these for about 25 cents. And I will. Thinbit does not
make the groove tool I need. They will though, for about &175.00. I
have been through this before.
Eric

Not for nothin', but it seems to me that for $125 total project income (500 pieces at $0.25 each), you're going to have a tough time making a profit on this. You've probably spent more than $125 worth of time just thinking about the tooling.

After 30+ years in business, I've learned that there are some jobs you just ought to walk away from. Tell the customer he can buy the parts for $2.90 from Zago.

Just sayin'

And yes, I would definitely consult with the o-ring manufacturer on this. Then you have so real, informed backup for your decision, other than Gunner's "Ayup."

On Fri, 17 Apr 2015 13:55:38 -0400, "Carl Ijames"
wrote:

wrote in message ...

On Thu, 16 Apr 2015 20:35:10 -0400, Bob Engelhardt
wrote:

On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section? Grooves
are usually rectangular to allow the o-ring to squish in compression.
The groove is square cross section.
================================================= =============

I hope you meant rectangular, not square. The oring is deformable but not
compressible, so the cross-sectional area of the groove needs to be bigger
than the cross-sectional area of the oring else you extrude and cut it on
tightening. As for the geometry you could do it with a sketch and trig but
I would prefer to just draw it in a cad program. Being a lover of run-on
sentences here's how I would do it in autocad. Draw an angled line to
represent the angled side of the flat head, draw a line perpendicular to
that for the end of the oring groove closest to the threads, make an offset
copy of the first line offsetting by 80% (or 75% or whatever you choose from
the Parker oring handbook for your oring and pressure and oring life but it
almost always works out to be between 75 and 80%) to be the bottom of the
groove, draw a circle for the oring tangent to the side and bottom of the
groove, and finally an offset copy of the first side line offset by 125-150%
of the oring diameter to be the second side of the groove (this creates the
extra cross-sectional area for the oring to deform into, and isn't critical
so long as it is large enough). Draw a line parallel to the screw axis
offset from the center of the oring by the radius of the ring (which also be
the centerline axis of the screw), trim all the original groove lines to
just leave the rectangular groove, then reflect everything around the
centerline axis. Now add the top of the flat head and the threaded section,
trim the excess from the angled lines, and you can pick off the dimensions
you need. That's the stuff I'm sure off, the actual machining I'm less help
with. On a manual lathe the way to do this would be to use a tool with a
squared-off end like a parting tool and rotate the compound to the right
angle and just plunge the compound. On a cnc couldn't you grind the end of
a boring bar to the parting tool shape at the angle you need, and then make
the angled plunge cut to simulate the straight plunge of a compound link you
were turning a taper? Either way I don't see where you need any kind of a
radius on the cutting tool, except a tiny break on the two front corners to
leave a rounded chamfer at the bottom corners of the groove for stress
relief. Hope this helps some :-).

Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net

Greetings Carl,
I think you described in more word what I said in my first post.
Eric

On Fri, 17 Apr 2015 12:12:48 -0500, F. George McDuffee
wrote:

On Fri, 17 Apr 2015 09:24:09 -0700, wrote:

snip
The o-ring will be sealing against low pressure-basically water a few
inches deep. So the sealing cannot be helped by pressure or vacuum and
instead must rely solely on compression. The customer would rather use
stock o-rings that are available everywhere.
/snip
o-ring is overkill -- use flat rubber washer for face
compression seal.
George-The customer wants an o-ring. I said this. Plus a rubber washer
won't work because the screw needs to bear against the aluminum. If
there is a washer in between then the countersink needs to be changed.
And all the parts out in the field would need to be returned to be
re-machined. If just the screw is modified then my customer can offer
this screw to his customers if they want an upgrade. Look, I
appreciate all the advice about how an o-ring is not the best solution
but it is what my customer wants and in this case I agree. What I
really wanted to know is if my method for finding the radii of the
sides of the o-ring groove will work.
Thanks,
Eric

On Fri, 17 Apr 2015 12:00:26 -0700 (PDT), rangerssuck
wrote:

On Friday, April 17, 2015 at 12:50:11 PM UTC-4, wrote:
On Fri, 17 Apr 2015 10:40:37 -0400, Joe Gwinn
wrote:

In article ,
wrote:

All-
I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved. I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?

From the rest of the thread, a picture or sketch would be very helpful.

People already make screws with O-ring seals: http://www.zago.com/.

And, Kaiser Tool Company makes lathe tool bits for cutting circular
grooves at various angles. I think that their ThinBit line is what you
seek. http://www.thinbit.com/

Joe Gwinn
Greetings Joe,
Zago does indeed sell those screws. $2.90 each in quantity. I need to
be able to make these for about 25 cents. And I will. Thinbit does not
make the groove tool I need. They will though, for about &175.00. I
have been through this before.
Eric

Not for nothin', but it seems to me that for $125 total project income (500 pieces at $0.25 each), you're going to have a tough time making a profit on this. You've probably spent more than $125 worth of time just thinking about the tooling.

After 30+ years in business, I've learned that there are some jobs you just ought to walk away from. Tell the customer he can buy the parts for $2.90 from Zago.

Just sayin'
I get paid for tooling and setup and programming and engineering. Then
I get paid per piece. The job will come up several times a year. Each
time it does I get paid for setup and tool attrition.
Eric

Greetings Carl,
I think you described in more word what I said in my first post.
Eric

So my post should have just been "yes"? :-) :-) :-)

Regards,
Carl Ijames carl.ijames aat deletethis verizon dott net