Achieving A Phonographic Finish

allloutmx · May 3, 2017

Im quoting a job that spells out a 500-1000 phonographic finish on two sides(round part with two flats). I would like to stand the finished turned blanks upright in the vice and use radial chip thinning to remove the bulk of the material. Part is 1.00" in dia and the flat finished at .500" centered. Im not sure how I will achieve the finish requirements by side milling. Are there special cutters to serve the purpose? Would ramping down the wall suffice? Material is 17-4. qty 2000pcs. Only other idea is to lay them down in the vice and do half at a time with a face mill.

Thanks In Advance! :cheers:

Booze Daily · May 3, 2017

I've never heard of a phonographic finish, but in one situation where my customer wanted a coarse looking lined finish I used a HSS corncob to finish a wall by side milling.

Mtndew · May 3, 2017

allloutmx said:
Im quoting a job that spells out a 500-1000 phonographic finish on two sides(round part with two flats). I would like to stand the finished turned blanks upright in the vice and use radial chip thinning to remove the bulk of the material. Part is 1.00" in dia and the flat finished at .500" centered. Im not sure how I will achieve the finish requirements by side milling. Are there special cutters to serve the purpose? Would ramping down the wall suffice? Material is 17-4. qty 2000pcs. Only other idea is to lay them down in the vice and do half at a time with a face mill.

Thanks In Advance!

I've never heard of that term to be honest. Is it supposed to resemble a record? can they be faced in a lathe to achieve this finish?

allloutmx · May 3, 2017

Mtndew said:
I've never heard of that term to be honest. Is it supposed to resemble a record? can they be faced in a lathe to achieve this finish?

Exactly..like a record. The ends will be finish turned by customer with the desired finish as well. The flats need to be milled in. imagine a soda can 1" in dia and you take .25" off per side leaving a .5" lug in the middle.

Larry Dickman · May 3, 2017

I though maybe with a phonographic finish, if you ran your thumbnail across it you could faintly hear Thomas Edison reciting Mary had a Little Lamb.

Never done it myself, but I've seen people use a threadmill to lightly groove up a surface to increase the roughness.

dstryr · May 3, 2017

Use a corn cob rougher style tool side milling. Should work.

ghost_rider · May 3, 2017

I would get in contact with the customer. A phonographic finish is usually meant for sealing gaskets on a flanged surface. If he needs just a rough surface I would show him some surfaces that are created using roughing cutter. if he truly needs a phonographic finish you might need to use a key cutter with a 60deg included angle.

KilrB · May 3, 2017

A "phonographic finish" has a spiral groove and will have to be done in a lathe or with a boring/facing head in the mill if that's truly what they want..

EPAIII · May 3, 2017

I also never heard the term but it seems to be fairly well known in gasket sealing circles.

phonographic finish - Bing

In reading some of the sites returned by that search, it would appear that a 90 degree tool is the most popular for this kind of work. Also a spiral nature appears to be common but I don't know if that is necessary. It would be automatically produced with a lathe and power feed on a facing cut. There are also frequent references to having this finish to rise a bit above the area where the flanges are bolted to assure a proper seal.

dgfoster · May 3, 2017

It's really quite simple---just turn at 78, 45, or 33 1/3 RPM. Groovy results guaranteed.

Denis

Hazzert · May 3, 2017

dgfoster said:
It's really quite simple---just turn at 78, 45, or 33 1/3 RPM. Groovy results guaranteed.

Denis

Just adjust rpm to musical tastes?

An indexable engraving tool taking a light cut would probably be my choice if I wanted that surface finish on floor a surface.

Forrest Addy · May 3, 2017

If you've ever worked on steam valves and pipe flanges you had to contend with phonographic finishes. This was a finishing technique for steam gasket finishes where flexitalic or spiral wound metal/asbestos (or present day replacement) gaskets were employed. In this a long chevron shaped stainless ribbon is spiral wound with a thin layer of mineral fiber to make the sealing element retained in a washer intended to be held centered by the flange bolts. .The chevrons buckle under compression of the flange bolts biting into the phonographic finish and the mineral fiber interleaving compresses to form a leak proof seal. It's a very efficient and effective gasket tolerant of mis-alignment.

In a phonographic finish the final pass is made with with a 90 degree v shaped tool using a 0.032 radial feed with one cut 0.010" deep. The finish looks rough and crude but when lightly dressed with a smooth file to remove snaggles the finished flange boss is ready for service. There's a standard on it. Here's a Google search result:

https://www.google.com/?gws_rd=ssl#q=phonographic+finish+flange

I'm told the same finish is used in chemical and oil refinery connections and other services where piping connections are subjected to high pressure and high temperature.

The OP text suggests to me the work he's quoting for a "phonographic finish is rectangular. Strictly speaking a simple coarse finish will not qualify. The finish has to feature shallow V grooves intended to grip gaskets oer sealant. If the phono finish is intended to seal against pressure the pattern should probably lay at right anges tot he pressure.

redlee · May 3, 2017

Ive cut thousands of Phonographic finishes. Valve industry.
The spec we had was a .06 rad tool set at .023 -.030 crosslide feed to achieve a 125-250 rms finish.As Forrest said its to hold the gasket in place and make a seal.
Flanges General - Flange Face Finish - Stock Finish, Spiral Serrated Finish, Concentric Serrated Finish, Smooth Finish
Something like this. (Stock Finish)

Cole2534 · May 3, 2017

Exactly. And if you skip it, the gasket may turn into a projectile.

Philabuster · May 3, 2017

allloutmx said:
Im quoting a job that spells out a 500-1000 phonographic finish on two sides(round part with two flats).

Exactly..like a record. The ends will be finish turned by customer with the desired finish as well. The flats need to be milled in. imagine a soda can 1" in dia and you take .25" off per side leaving a .5" lug in the middle.

Sounds like they just want the same "average roughness value" on the milled flats as the ends that will be finished turned by the customer. No way to achieve the phonograph finish on a milled surface.

allloutmx · May 3, 2017

Good reads.. I learned a lot...again. Met with the customer this afternoon, and the function of the surface finish is for the epoxy to adhere too and the direction of the pattern is not critical.

Phil- maybe Im still a little miffed on the exact definition but if I were to take a 90dg double angle milling tool around the perimeter of the part cutting at any specified pitch, would that not be a Phonographic finish?

Ron Hofer · May 3, 2017

A phonographic finish doesn't have to look good; it only has to sound good.

JRIowa · May 4, 2017

allloutmx said:
the function of the surface finish is for the epoxy to adhere too and the direction of the pattern is not critical

Your customer doesn't even know what a phonographic finish is! As others have said, it's a flange finish for pressure retaining fittings. It's one of the 3 major types: Flat, Concentric, and Phonographic. Flat is used for low pressure only, less than class 100. Concentric will take more pressure than phonographic because it doesn't have a built in leak path.

It sounds very much like you customer just needs a 125 finish. I think I'd Blanchard grind both side and then sandblast. Seriously, get or make a rear vise jaw with 2 Vees in it. Lay the parts down and blast across them with a facemill, turn over and come back. It doesn't sound like rocket science, but you never know.
JR

DDoug · May 4, 2017

Ron Hofer said:
A phonographic finish doesn't have to look good; it only has to sound good.

Doug Sax's (posted in an interview) mastering lathe would vary the pitch, to make room for the louder passages..... :crazy:

DDoug · May 4, 2017

JRIowa said:
It sounds very much like you customer just needs a 125 finish. I think I'd Blanchard grind both side and then sandblast.
JR

I think you'd have to be using fractured steel grit to get that finish, and have a means to grade and maintain the grit size/sharpness for repeatability.

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