Machining slots for toric joints (o-ring)...

[Externet]

I think they are called 'glands' when on a flat surface.

What is a proper tool to machine the 'nesting' for o-rings on bronze ? Would hole saws like these work : ?

 

----> http://g02.a.alicdn.com/kf/HTB1GC9kIVXXXXX5aXXXq6xXFXXX1/6MM-8MM-10MM-12MM-15MM-16MM-18MM-20MM-22MM-30MM-Diamond-Coated-Tool-Drill-Bits-Hole.jpg

 

----> http://img0.ph.126.net/YOwISOkx75ndkvzu3D3Dnw==/6619241418630639771.jpg

 

Or something else ?

[Enthalpy]

Hi Externet,

 

It depends on where your O-ring shall seat, and unfortunately I lack English vocabulary here.

 

If you have freedom in the way you split the parts, it may be possible to have only shoulders in all parts, which is easy to machine. Better solution, even if this needs more parts or more O-rings.

 

When you need a groove and the parts are in an other, the proper tool does it if the part fits in a turning machine; noncylindrical parts instead are machined by milling, but usually not with a milling cutter: a fitting holds an eccentric single-tooth tool like this

https://en.wikipedia.org/wiki/File:Universal_Plan-_und_Ausdrehkopf_von_Wohlhaupter.jpg

I didn't find the eccentric adapter's English name. Wohlhaupter in French like the name of a company, and Ausschlagfutter in German. Maybe a boring head.

 

If the parts are butt and you need a groove, you may still try the eccentric tool holder, but the working conditions are horrible for the cutting tool. It's better to use just a usual narrow milling cutter moved in a circle by a CNC milling machine. Though, an O-ring demands smooth surfaces, which isn't automatic with CNC machines. As well, too narrow milling cutters are fragile.

 

With a narrow milling cutter and without CNC, one would have hold the part in rotating vices (approximate name) in the milling machine's table. One hour to half a day adjustment time.

 

Don't forget to specify the tolerances and the smoothness of the groove in a drawing, because O-rings have special needs, indicated by their manufacturer in the catalogue.

 

Catalogues of O-ring manufacturers often propose design variants for the grooves, and experts at the manufacturer can check you design and give advice. Exactly this point in a design can cost one minute machining and work properly, or cost half a day and fail, so invest the necessary engineering time.

[Externet]

Thanks again for your permanent good assistance.

 

Just an image, single tooth...----> http://www.centroidcnc.com/images/cnc_block/oring_groove_600.jpg

[Enthalpy]

Yes, that's it. This is difficult for the tool because

- It must fit in the curved groove it cuts

- The chip must come out despite the groove is curved.

 

If you can make a shoulder at the cylinder instead of a groove, and then an other shoulder at the head instead of making it flat, this step of machining is easier. The O-ring then fits between both shoulders.

 

Whatever the design you choose, mind at what side of the ring the sitting plane of both parts is: it must retain the ring pushed by the pressure.

 

And of course, don't forget the proper screws and pre-tensioning. The screws must press the head stronger than the fluid will: it's not just a matter of resistance, but really of pre-stressing - or else the O-ring gets extruded. At a past employer, we had 24mm screws all around a cylinder, but bigger is often necessary. One practical limit is 16mm (100kN), the maximum possible to tighten with a simple wrench.