Tolerance Block "Crossout" - Per what std?

[SolidWorksGuru]

Our company has always crossed out (big "x" from corner to corner) the Tolerance Block on our std sheet formats whenever it didn't apply to the drawing. For example, if it's a control drawing of a WASHER, we will specify a size of 0.094"ID x 0.250"OD x 0.032"THK. Those are parameters that purchasing uses to order the right size, but I don't want inspection to be checking the washer dimensions within .005. So, we cross out the Tol Block to indicate that it does not apply.

This practice is now being chalanged by our new director of QA!!!

Does anyone know what standard this comes from?

Chris Wilson
CAD Administrator
CSWP

 

[SolidWorksGuru]

So your suggesting to put roughly +/- 1/16" tolerance on the 1/8" dimension, right? I guess thats ok since anything out of that tolerance would make it a differant variation number.


Chris Wilson
CAD Administrator
CSWP

 

[KENAT]

drawoh, that was my point, hence option A is not to have a drawing, option B if you must have a drawing is essentially just a drawing invoking the spec and providing a reference illustration. To me the drawing in this situation is superfluos but I'm not going to lose my job by refusing to create one, though I'd suggest we could do without.

SolidWorksGuru, your pdf example definitely needs some kind of tolerance on the 1/8" incremements. No I don't think +-1/16" tolerance is necessarily what was being proposed, though if functionally that's what works then fine.

You want to spec the losest tolerance that ensures function, if that's +-1/16 great, if it's +-1/8 great, if it's -0 +1/8 great. Think about how the parts are used, the fit/function involved and tolerance accordingly.

(On another issue that came up, Just because it's a purchased part, doesn't necessarily mean no drawing is required, in fact that's specifically what some of the 'control drawings' are for.)

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[MechNorth]

If you're dealing with industry-standard purchased components, reference the standard on the drawing. The industry standard thus overrides anything on the drawing. For common washers, look into ASME B18.21.1 & B18.22.1 for inch-series, and ASME B18.21.2M and B18.22M for metric. For specialized washers, look into ASME F436, F436M and IFI 534. There other standards applicable to ISO, DIN, JIS, and many other national standards, depending on where you are sourcing and using the parts.

I don't know of any standard that says anything X'd-out is to be ignored, though it is common practice. Of course, common practice isn't defensible in a legal context.



Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fcsuper]

I personally wouldn't cross out the block. It would edit the information to make it apply to the drawing. Cross outs are pretty clear, but any unused specifications left on the drawing can come back to haunt you.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

I'd disagree with fcsuper, I wouldn't edit the block. People can get used to what the block usually says and don't always notice if you've changed it. Having different blocks for things like cables or castings can make sense but just changing the block willy nilly can cause errors.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[ewh]

I agree with KENAT for the same reasons. True, the fabricator should read the title block of every drawing, but in reality assumptions are often made which could result in rejected parts if the title block information has been changed.
We treat drawing format as a form and control it as such. The title block is pretty much boiler plate, and any information that differs from that in the title block is clearly noted elsewhere on the drawing.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[drawoh]

KENAT,

I will give you an example. I specify a fan. I provide a drawing showing the dimensions. In notes on the drawing, I state that the fan is 12VDC, and that it delivers 60CFM at 0.1"H₂O. I try to provide more than one manufacturer and part number.

If there are problems getting the specified fan, purchasing can find a similar fan that meets the requirement. If necessary, they can send my specification out to a vendor to see if they have anything.

If there are issues with the cooling, engineering can see what kind of fan I selected, and have some clue as to why I selected it.

Fans are standard, manufactured parts. I cannot see why someone would do a dimension inspection on it. My dimensions are for reference, only.

JHG

 

[KENAT]

Drawoh, there must be something in my grammar or something that's misleading as I'm not sure what we're going back & forth on.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[ewh]

Could it be the accent?;-)

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[drawoh]

KENAT,

I was responding to your comment further up about option[ ]A. If nothing else, I would like MRP stock codes to be based on a document somebody can locate and read.

I set up the title blocks here. Our title block is minimal, with boxes for the company logo, the title the drawing size, number, revision and pages, and a signature block. We add blocks on to it, depending on what we need. We have fabrication blocks for English and metric dimensions, we have an assembly block, and a drawing projection (third-angle) block.

On an A-sized fabrication drawing, I do not apply the fabrication block. I just type in a note stating that dimensions are in millimeters, and that dimensioning and tolerancing are as per ASME Y14.5M-1994. Obviously, in the absence of standard tolerances, I have to be careful to apply complete dimensions.

Given that ASME Y14.5M-1994 requires you to remove trailing zeros on millimeter dimensions, you have to tolerance everything manually anyway. The standard tolerances are not much use.

JHG

 

[KENAT]

For my option A, I was thinking of how standard hardware was called up, based on the washer example, not necessarily things like your fan example. By 'to a standard' I meant something to a recognized industry or national standard such as ISO, ASME, ANSI, MIL-STD...

For your Fan example you could either go whole hog standards compliance with a control drawing or something simpler if it fits your needs. I agree that just having a vendor part number isn't always adequate.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[drawoh]

KENAT,

On second thought, it was the accent. Yeah, it was the accent.

JHG

 

[fcsuper]

KENAT,

I know where you are coming from regarding editing title blocks. I instinctly had the same impression. However, after implementing the modifiable title block at my company, no issues have arise, and there's even been some grateful comments from various parties.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

I've actually encountered the issue of errors being caused by the changed title block tolerance, so hence I'm generally a'gin it.;-)

Back in the UK though where, being mostly metric we only had a single value block tolerance, not varying by decimal places, we just put whatever value was most appropriate for the drawing.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?