Unknown Drawing Symbol 1

[resjsu]

Hello All,
Please refer to attached PDF for circled symbol in question. I have tried googling a description of this symbol but have had no luck. Does anyone know what the symbol means and what the value next to it represents?

Thank you,
Aure

 

[ctopher]

That's a first for me. Whatever it means, it's too close to the dim lines to be clear.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[resjsu]

Yes, it is actually on the extension line. I was assuming it had something to do with surface finish but there is already a surface finish callout. Thinking it may be an older symbol, since the drawing is a little older, I have been tyring to get my hands on an older "Machinist Handbook" but have had no luck.

 

[dhengr]

Resjsu:
The “italic f” is a surface finish mark, the cross mark, hash mark is on/intersects the line (surface) to which it applies. The “italic f” preceded the newer 60̊ V as the std. finish mark. I’m not sure what the 3.0 means, you have to study the drawing and the full indication with the V to the left. Take a look at some older Mechanical Drawing textbooks.

 

[resjsu]

Dhengr,
Thank you, this gives me a bit more to go off of. I will try to locate an older machinist handbook and check there for more info.

Thank again,
Aure

 

[dgallup]

Googling that came up with this in Wikipedia:

An italic f (Latin small letter f) written on a line representing a surface was an old way of indicating that the surface was to be machined rather than left in the as-cast or as-forged state. The "f" came from "finish" in the sense of "machine finish" as opposed to raw stock/casting/forging. Later the ASA convened upon a letter V (specifically a sans-serif V) touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value (RMS, microinches or micrometres) for the machined finish, to be measured with a profilometer.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[tbuelna]

Very interesting. I have made many drawings for machining of castings or forgings over the past 25+ years, but I have always used a system of coordinated datum target points to define the initial orientation of the cast/forged part.

If what others state is correct, this would seem to indicate the initial machined surface must have a profile tolerance within 0.35mm of datums A,B,C, a max surface roughness of 3.2 micrometer, and a max stock removal of 3.0mm. Normally, this machined surface would serve as the basis of all subsequently machined features. But since there is no dependent datum attached to the profile tolerance, this would not seem to be the case.

 

[Occupant]

By itself it only means machine finish, permissible roughness 3 microinch and you have to go back maybe 40 years to have used it. But now I am dating myself (not that anybody else would - yes, I know my "Dilbert".

 

[chicopee]

I managed to find my old Engineering Drawing textbook by Thomas French and an excerpt is attached confirming above responder about an italic f for surface roughness. On drawing prints, surface roughness would be indicated in the titleblocks, however, that value 3 appears to be an exception. That value 3 as mentioned above is in micro inches. You will also note that the roughness symbol has changed over the years to a V shape and then to a lazy J shape. I would say that you should maintain a library of older reference books which you can purchase relatively cheap from used bookstores around colleges and universities. When I say older reference books, I am taking about editions of the 40's, 50', 60's.

 

[racookpe1978]

Then, is the datum (for all future measurements and surfaces) the "after-finished" 3.5 m surface? Not the 3mm machined margin from the casting?

 

[tbuelna]

The italic f does not indicate surface roughness. Surface roughness is indicated by the value with the check mark. And since the drawing dimensions are metric, the surface roughness value is in micrometers and not microinches.

 

[Occupant]

If this was a metric drawing the surfaces finish 50 years ago would have been entirely specified by a series of triangles (1 to four) that are related to micrometers. There never was a italic f in any metric drawing that I have ever worked with and I go way back.

 

[resjsu]

Lots of good information and I appreciate all insight. Can someone translate what the symbol and value mean into a sentence?

 

[Jboggs]

resjsu: Unfortunately since the symbol is not part of any current standard, the most accurate way of interpreting it is this: "It means what the designer/draftsman intended it to mean." If that person is not available for you to ask go to Plan B: get clarification from your customer or final end user of your part. After all, they are the only true source to tell you what they want, regardless of ANY comments on this forum. And if that isn't an option, then go to Plan C: the symbol simply means the surface is to be machined. Period. If there is some standard finish comment elsewhere on the drawing that might help you to determine the final finish, but other than that your best judgment is your only guide.

 

[robyengIT]

in metric system (many years ago, at least 35)see attached table

 

[tbuelna]

resjsu-

As Jboggs noted, there is no standard meaning for this symbol. Since the image you provided appears to use a current system of GD&T for all of the other dimensions, you should refer to a standard like ASME Y14.5-2009.