What does 'Benching of Welds' mean? 1

[KirbyWan]

Howdy all,

I work on aircraft and ran across the follwing term that stumped me and I was wondering if the community could enlighten me.

In GE SPM 70-24-00 "Etching procedures for fluorescent penetrant inspection" it states: "Smeared surface material, caused by operations such as benching of welds, can mask cracks and flaws in metal parts preventing identification during the inspection process." I asked our two most experienced welders and one thought it was similar to a peening process, the other was thinking it just meant grinding, as in using a bench grinder, but both were unfamiliar with the term as if it was no longer commonly used or at least not used for what we work on.

A quick google search showed that some people are using the term to indicated a surface finishing technique, without actually describing what is being done, commonly done to molds apparently. It also gives a wikipediea link to sawfiler where it seems to be a peening/coldworking process to relieve stresses in the large circular saw blades of lumber mills.

Could someone please provide a definitive definition of benching with repsect to welds so I can be sure to understand GE's requirements?

Thanks all,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[gtaw]

It typically means sanding, grinding, etc. which has a tendency to smear soft metals like copper, aluminum, etc. It tends to obscure small or narrow surface breaking discontinuities such as cracks, porosity, etc. Etching removes the smeared metal so liquid penetrant can be drawn into the now open discontinuity.

Once the etching process is completed, the part must be flushed with clear water to remove any etchants from the discontinuities and dried completely. The etchant can "poison" the penetrant so that it is not as visible. Acids tend to destroy the fluorescence of the penetrant so that it does not "glow" when exposed to ultraviolet (black) light.

Best regards - Al

 

[KirbyWan]

gtaw,

Thanks for the response. I'm fairly well read about the FPI process, and I understood where they were going from context, other specs say don't grind on welds before FPI, but I wanted to make sure I understood exactly what the phrase "benching of welds" meant. Can it include peening processes? Wire brushing? Is it related to the surface finishing process on the websites that talk about benching of molds? How broad or narrow can the process be? If it was just 'don't grind on welds' I would think they were using a far too obscure term. Is this term used more in other industries?

Thanks,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[MintJulep]

"Bench work" is the term used when the machinist works at the bench with hand tools rather than with machine tools, and involves such operations as ... filing, hand sawing, chipping, deburring, ... scraping, hand tapping, ... hand honing and polishing...

 

[berkshire]

Part of AC 43 13 in the welding section frowns on the practice of "Benching " welds.

The section is listed under , Practices to guard against, and starts off by saying " Do not file welds in an effort to make a smooth appearing job".
However having said that, I have worked in aircraft shops where a part of the overburden on a weld has been removed to make a part fit another one.
B.E.

 

[KirbyWan]

Thanks MintJulep, and berkshire.

I looked up the reference in AC-43-13 and Cpt 4 Section 81 "Practices to guard against" indicates to not file or grind welds and don't fill welds with braze or solder metal. It doesn't use the term benching but from the three repsones I have so far it seems like benching refers to filing and grinding of a weld. I assume wire brushing is included in this and maybe peening process as well.

Still not as clearly defined as I would like, it appears to be a catch all phrase along the lines of MintJuleps reference for touch up using hand tools and the benching of molds is referencing the hand sanding/polishing of molds to remove tool marks from where the mold was CNC machined. If anyone else has more to add please feel free to chime in.

Thanks all for your repsones,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[Guest102023]

I've never heard of it, and I am surprised such a large and sophisticated company would use such a non-standard term.

The term benching should be benched, I might say. But I won't.