TOLERANCE STANDARD FOR SHEET METAL FEATURES

[K.P.M.]

Hello everyone,

We normally provide features like holes size, corner radius, chamfer, bending radius with nominal value only in sheet metal drawing. Now our vendor is asking for tolerance or any specific tolerance standard for those features.

Please suggest standard.

Thanks,
KPM

 

[ctopher]

All drawings should have tolerancing for dimensions.

Chris, CSWP
SolidWorks
ctophers home

 

[powerhound]

The first fundamental rule in ASME Y14.5-2018 states that each feature shall be toleranced. The word shall in that version of the standard establishes a requirement.

John Acosta, GDTP Senior Level

 

[3DDave]

I think ISO has a volume for "we don't care what the variation is but here are some numbers to make the vendor happy."

General ISO Geometrical Tolerances Per ISO 2768

"ISO 2768 Part 1 is intended to simplify drawing indications and it specifies general tolerances for linear and angular dimensions without individual tolerance indications in four tolerance classes. It applies to the dimensions of parts that are produced by metal removal or parts that are formed with sheet metal fabrication." from

https://www.cnclathing.com/guide/ge...sions-iso-2768-tolerance-chart-pdf-cnclathing

You do need to specify the class of tolerance, from Fine to Very Coarse, but it is just a note on the drawing.

Good luck on getting what you expect.

 

[supergee]

K.P.MISTRY

The way you used to work is dangerous but often found in sheet metal industries. A lot of companies do not use tolerancing when the machines used to manufature the part are much more precice than the design requirement.

Example : if my design can accept a ±.031inch error on a part which is made with laser cutter with a precision of .005. Realistically, I will probably never have any problems.

This been said I do not recommand such practice, especially when outsourcing, because if a conflit occures, you have no recourse against the manufacturer. Your vendor probably knows about that, and wants to protect itself too. Also, as I say to my students, why though away money on an expensive laser CNC when a less expensive turret punching cnc can do the job?

I would at least put a note saying unless otherwise specify tolerance of a profile all over. see ASME y14.5 2018 figure 11-10 or ASME y14 2009 figure 8-8 for more detail.

Gee