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O-rings sealing.......

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sandman001

Just Freeze It
Joined
Mar 11, 2003
Basically my question is, why would you need an O-ring groove?

Seems to me if you just put an O-ring in there and put enough pressure down on it that it couldn't move, and would then be compressed between the top and bottom of the block.

Seems to me it would work just as well as with a groove?
 

CrashOveride

Member
Joined
Jun 22, 2002
Location
Beijing, China
It might movea round though, don't want that. I think it is better to just be sure it won't move at all and put a little grove in, after all the extra machine time is marginal for somthing like that. But if I were making a block I wouldn't both with a groove.
 
OP
S

sandman001

Just Freeze It
Joined
Mar 11, 2003
While I agree that a groove is better, it's hard to machine a good groove.
 

ILikeMy240sx

Member
Joined
Sep 28, 2003
Location
University of Michigan
Yes groove is necessary as it is difficult to get an optimal contact between the top and bottom plates without it... It provides a "niche" for the oring to sit and not warp or anything like that...

As for the difficult to maching part... yes thats very true and for the groove to be successful (you prob are aware of this...) it needs to be very precise...
 

CrashOveride

Member
Joined
Jun 22, 2002
Location
Beijing, China
sandman001 said:
While I agree that a groove is better, it's hard to machine a good groove.

Is it really? I mean it's just a smoothed indentation in the shape of a circle. When you consider what the waterblock manufacturers are doing for their waterblock allready I doubt that the little groove is hard to do... I have worked with CAD stuff and it wouldn't seem hard at all...
 

Pyros

Member
Joined
Oct 6, 2002
Location
Lost in life
How hard the groove is depends on the design of the block and what kind of milling machine you are using. I endmill various types of grooves everyday at work on a HAAS Mill and as long as you know how to write the program, its nothing. Of course not evertone has access to $90,000 mills and mastercam. ;)

If your wanting to "sandwich" a o-ring between 2 pieces of the block, the less square the groove is, the easier it will be to use the o-ring IMO.
BTW, on my homemade block, I found it was easier not to use a o-ring because of the small size of the block which would cause the groove to have near 45* angles.
 

Diggrr

Underwater Senior Member
Joined
Nov 29, 2001
I believe the groove is handy if your design needs it to be other than it's origional round shape. My slitedge's hold it into an almost square shape, which would be near impossible to do while trying to put the top and bottom together.

Also, the seal is more reproducable, because in a production setting, one scratch in the copper might let the block leak. A groove gives it 3 sides to seal against.

For a one-off block, there's no real rule that you have to use a groove, if your design is round or your patience allows you to hold the bottom and top together while fidgeting with an o-ring on four sides (each time you open it).

Hand tooling would be a pain to make a groove, and some mills I've seen aren't that good at matching up the cuts when you come around to the beginning, but with patience and a good memory of the crank markings where you begin can help.

Have a good one!
 

VballCoach

Member
Joined
Oct 16, 2003
Location
5min from Philly Airport
I tried using a rotozip to make an oval groove...it almost worked but the pressure on the o-ring was uneven and the plastic top bowed and leaked at the center barb.
I ended up soldering a 1/8" top instead of the cool looking 1/4" see-thru plastic. Better to be safe than sorry. Also, the copper can be polished to a mirror shine.
 

JFettig

Hey! I showered! Senior
Joined
Jan 5, 2002
Location
MN
The O-ring needs more sealing area, and putting a groove in there allows the top to fit flush with the bottom, An O-ring also needs to be supported, its not suposed to be streached either.

Pyros: It doesnt take a 90,000 mill to make an O-ring groove, I made one on my $500 manual mill, will be a aprox $1500-2000 cnc mill with almost as good as your haas acuracy.
Btw, it doesnt take mastercam to make a groove, all it really takes is knowledge of G-Code and a little drafting.

Jon