Surface finish for sealing flange face - How to machine?

R

robert123

Stainless

Joined

Apr 8, 2012

Location

AR, USA

• Apr 19, 2018

• #1

I have a part we are getting ready to machine on a lathe. It says to machine the flange face with a circular lay (concentric of 500-1000 RA or spiral 125-250 RA) produced by machining 30 to 80 cuts of uniform depth per inch of face width.

This sounds like instead of facing the part, we should move the tool into the face (Z move), back out, move down, and repeat about 50 times per inch. This would certainly give a concentric pattern, but how could you get a spiral doing this? Or am I reading this wrong?

 

N

NodecoMachine

Cast Iron

Joined

Sep 7, 2011

Location

NJ, USA, Lebanon

• Apr 19, 2018

• #2

Think more like a face tread. They spec it like this so the crests of the surface finish get crushed against the mating surface to create a seal. And just to be clear I do not mean that they want an actual face tread, just the general spiral pattern with specced surface roughness...

 

A

adama

Diamond

Joined

Dec 28, 2004

Location

uk

• Apr 19, 2018

• #3

NodecoMachine said:

Think more like a face tread. They spec it like this so the crests of the surface finish get crushed against the mating surface to create a seal. And just to be clear I do not mean that they want an actual face tread, just the general spiral pattern with specced surface roughness...

Click to expand...

Not realy crushed, more bite into and capture the gasket so the gasket does not extrude at high line pressures

 

JRIowa

Diamond

Joined

May 27, 2003

Location

Marshalltown, Iowa, USA

• Apr 19, 2018

• #4

NodecoMachine said:

Think more like a face tread.

Click to expand...

That would be phonographic serrations. The OP said circular which to me means concentric.
Just do a Google on "Flange Serrations"
We did millions so we had special tooling. We even had written proceedures for machining and inspection.
JR

 

R

Red James

Stainless

Joined

Jan 26, 2013

Location

Plainfield, Indiana, USA

• Apr 19, 2018

• #5

To the OP ... the 'or' is significant in the instructions, meaning 'not both'.

 

N

NodecoMachine

Cast Iron

Joined

Sep 7, 2011

Location

NJ, USA, Lebanon

• Apr 19, 2018

• #6

I have a part we are getting ready to machine on a lathe. It says to machine the flange face with a circular lay (concentric of 500-1000 RA or spiral 125-250 RA) produced by machining 30 to 80 cuts of uniform depth per inch of face width.

Click to expand...

I guess it could be either? It is a bit confusing after reading it a couple times.

Not realy crushed, more bite into and capture the gasket so the gasket does not extrude at high line pressures

Click to expand...

Sorry.

 

Bobw

Diamond

Joined

Feb 8, 2005

Location

Hatch, NM Chile capital of the WORLD

• Apr 19, 2018

• #7

The OR makes it a simple facing operation..

You just need to crunch the #'s to find your nose
radius and feed rate.

 

B

Booze Daily

Titanium

Joined

Sep 18, 2015

Location

Ohio

• Apr 19, 2018

• #8

For concentric grooves I think I would just use a roughing canned cycle feeding to Z0. DOC for 50 grooves would be .020

For spiral grooves, just make a facing cut at F.02 (again for 50 grooves per inch).

You'll have to experiment with the number of grooves and TNR to get the Ra specified.

 

eKretz

Diamond; Mod Squad

Joined

Mar 27, 2005

Location

Northwest Indiana, USA

• Apr 19, 2018

• #9

Not confusing. It seems to be a pretty clear spec of EITHER 500-1000 Ra concentric grooves OR a faced (phonographic/spiral style) 125-250 Ra finish. We used to make these gasket surface all the time for one customer in the valve industry. They had specs for tool shape, groove depth etc. Might have been JR's company being that he's in Iowa and so is the HQ of this customer.

 

T

Triaged

Aluminum

Joined

Dec 31, 2016

• Apr 19, 2018

• #10

Kennametal.com had a surface finish calculator that will come in handy.

R.0156, F.0096, gives 188uin. Mess around with it and see what it takes
https://www.kennametal.com/en/resources/engineering-calculators/turning-calculators/surface-finish.html

 

JRIowa

Diamond

Joined

May 27, 2003

Location

Marshalltown, Iowa, USA

• Apr 19, 2018

• #11

It's not a simple facing operation. It's a very specific proceedure for making a gasket surface. It sounds like they are referencing ANSI/AMSE 16.5. The size and class of the flange designate what style serration is to be used. Like I said, done millions. Kretz probably did a few for us. You'd also better have some protection for them after they are cut. A scratch across the grooves would reject them at our facility. We used to make our own inserts for the concentric grooves. We cut so many serrations that at one time, we ran a TWEDM 3 shifts just to make the inserts.
JR

 

9100

Diamond

Joined

Nov 1, 2004

Location

Webster Groves, MO

• Apr 19, 2018

• #12

It depends on the material carried in the pipe. The "phonographic" spiral will have a tiny and long leakage path. For many applications it wouldn't matter but if it is carrying hydrogen or helium, small molecules, or a very high vacuum, it could cause trouble.

Bill