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Autofeed boring/facing head; short-term rental wanted, Minneapolis area (or ship from US address)

MZ

Aluminum
Joined
Dec 31, 2005
Location
Providence, RI
Vendor asked me for leads to rent an autofeed boring/facing head that's on, or adaptable to, CAT50 taper. They are reworking four 11.5" diameter flat o-ring seats for us and don't otherwise use this type of tooling. We require circumferential surface lay (UHV application), and the feature is in a large 304L plate that's too large for them to spin. PM or post here and I will put you in touch offline. I'm the customer, not the shop.
 
Just how wide is this o-ring seat? My first thought would be a plunge cut with a form tool would be the way to go.
 
Just how wide is this o-ring seat? My first thought would be a plunge cut with a form tool would be the way to go.
Thanks for your suggestion. The seal area extends .875" radially, ID is 8.00" but it must be single-pointed, with constrained tip radius and feed. It cannot be 'smooth', circumferential surface finish lay is an engineered feature.

We have several of these in service, last production was in 2011. Our current vendor just briefly needs this "traditional" tool to rework a few.

Thanks in advance,

Mike
 
What is the required feed rate? May eliminate some boring heads. For curiosity, what is the depth? I've never done vacuum service work.
 
Feed and tool tip radius are coupled; the finish spec is 32 +/- 8 microinch RMS (i.e., 24 to 40). So a range of combinations are suitable.

The part is actually a 68" circular flat plate and the seal is effectively flush (there is a shallow relief outside the o-ring zone just to ensure the mating part, which carries the o-ring in a conventional groove, bottoms out). This feature is off-center in the plate.

Ours is a non-standard vacuum application, using a dry Flourel o-ring as it is highly sensitive to contamination. The seal must resist atmospheric pressure from either the OD or ID direction, or neither (both sides at vacuum or atmosphere), depending on instrument state.

The "tooth" created by the spiral single point finish increases the effective local compression of the Flourel, improving reliability. It also evidently resists the tendency of the seal to "shift" radially when the direction of pressurization reverses. We think this helps it withstand cycles without developing leakage.

The overall system's operating base pressure is in the 1e-9 millibar range (often called "ultrahigh vacuum"). Total volume is about 20 million liters.
 
That 32 ( I'm guessing is actually a "tpi" rate?) would kick any boring/facing heads I'm aware of out of the running for your application. It's not a standard facing speed but more of a threading speed.
If however you could apply concentric rings rather than continuous, any boring head could work by making a cut, back out the tool, adjust, then plunge the next groove.


Otherwise you're going to need to rent a portable "Flange facing machine" to get continuous feed rates like that.

It sounds like you are describing a oil/gas flange face finish, which is what those are designed for.


Just curious,

Your vendor isn't looking for a boring/facing head for a Horizontal Boring mill??? Is he?
Those are much different than what I'm thinking about. And don't really align with your description. But may be capable of the task but since I don't have one yet I can't say for sure.
 
It's a 32μin RMS finish, not a feedrate. We used to have to make similar gasket surface finishes on stainless valve bodies. I'm not familiar with "circumferential" surface lay. Ours were always either "phonographic" (continuous spiral) or "concentric" (series of plunge cut concentric rings with specific geometry into a finer finished surface).
 
Correct, it is microinch RMS. I never heard "phonographic" but that and "concentric" are the same idea. Here is the drawing callout if anyone's interested. Really just needs an autofeed head, again we have made these before and current vendor is just short of a fairly standard tool.
 

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Correct, it is microinch RMS. I never heard "phonographic" but that and "concentric" are the same idea. Here is the drawing callout if anyone's interested. Really just needs an autofeed head, again we have made these before and current vendor is just short of a fairly standard tool.

No, not the same. Phonographic is a continuous spiral, like you'd find on a record or a normal faced finish on a lathe.

Concentric is a dip cut that forms a single round concentric ring, then retract the tool, move over, do it again; retract the tool, move over and do it again, etc.

These terms are usually used for flange gasket sealing surfaces though. You're just looking for what basically amounts to an o-ring groove bottom, yes?

It may be difficult to find someone willing to rent a boring/facing head. I sure wouldn't send one out to anyone I didn't know very well. They are extremely expensive.
 
You're just looking for what basically amounts to an o-ring groove bottom, yes?
Nah, he said the O-ring is in the mating surface. He needs to make or rework the plain flat surface with a specified finish. On a job like this I would not be trying to distinguish between spiral phonographic and concentric face grooves, because the surface finish is sufficiently fine you can't catch your fingernail on them. What the specifying engineer did not want was any radial leakage paths, and if they were originally made with a facing head, then spiral grooves were functionally satisfactory.
 








 
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