Inch marks or no inch marks??

Date 03-28-2008 20:08

Hello rework, and welcome. That is a good question. I am no engineer, just an inspector, but i pulled some training materials for blueprint reading and briefly glanced through a few manuals and nowhere did I see an " mark. I can not say that I recall ever seeing one used. In my opinion the " mark is unnecessary as I do not know what else 1/4, for example, would be interpreted as, other than a 1/4 inch . This does not mean squat when it comes to answering your question. However, I am quite sure that somewhere in the vast resources of knowledge accumulated in this forum you will get an answer.

By jwright650 (*****)

Date 03-28-2008 20:35

To take this a step further, I quickly breezed through AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination.

All fillet welds were shown without the " marks. also noted that even the intermittent welding is shown as 2-12 meaning it gets 2" of weld every 12"...never did I see any dimensions showing the " marks as I skimmed through the Standard.

By Jim12

Date 03-28-2008 20:46

does your firm utilize both metric and standard measurements like heavy equipment, that could be the only reason I would think.

By 803056

Date 03-28-2008 21:47

I believe it is industry practice to note the units of measure in the title box. Once it is established, units are not repeated on the drawing itself.

A2.4 does not include units of measure in any of their examples.

The can create a minor problem if you are working with some military standards. For example:

2 1/2 means 2 and 1/2 inches to me. In MIL-STD-22 they use the convention 2-1/2 as meaning 2 and 1/2 inches.

It drives my students crazy because they always ask, "Why does the symbols say 2 minus 1/2 inch, why don't they list it as 1 1/2 inch?"

Best regards - Al

By eekpod

Date 03-28-2008 23:12

Just remember, the object of the game is to make it clear, consice and easy for the USER of the drawings. If it takes away ANY question, I would advise you to add the ", if there is no question, and your people never worked with metric , you'll most likely be ok w/out them. Remeber it's for the shop personnel to understand, not you guys in the office to make yourselfs happy. Chris

By jrw159

Date 03-29-2008 02:30 Edited 03-29-2008 02:33

I have to agree with you on this. I have had more trouble in the past just getting engineering,they are busy, to put the neccessary information on the print, IE proper weld symbol, size, location, and God forbid if I need information on a groove weld that would require weld size, root opening, bevel %, finish contour and pertinant tail information. If they have the time AFTER the essential information is in place, then by all means use it. But is it manditory? I don't know.

By jrw159

Date 03-29-2008 02:23

Al,
did I miss somthing or are there some word missing in your reply?

"2 1/2 means 2 and 1/2 inches to me. In MIL-STD-22 they use the convention 2-1/2 as meaning 2 and 1/2 inches.

It drives my students crazy because they always ask, "Why does the symbols say 2 minus 1/2 inch, why don't they list it as 1 1/2 inch?""

Please clarify.

By 803056

Date 03-29-2008 13:56 Edited 03-31-2008 03:28

Let me try to clarify:

In one case the 2 inches and 1/2 inch is separated by a space. In the case of the military standard cited a "-" is used to separate the 2 inches from the 1/2 inch.

2 1/2 as compared to 2-1/2, both meaning the same thing. However, because most drawings (other than military) do not use the "-" separator, the students mistakenly interpret the "-" as a minus sign.

This can be confusing to someone unfamiliar with military nomenclature. For example, when the weld size is specified as a function of the wall thickness of pipe: 1-3/4T. The proper interpretation is 1.75 times the wall thickness (T). However, many students interpret the example 1-3/4T as 1 inch minus 3/4 the wall thickness.

Most drawings that use ANSI as the basis use the "-" separator to distinguish between feet and inches, for example: 1-2 1/2 typically is interpreted as meaning 1 foot, two and 1/2 inches. The symbol for feet (') and inches (") are not used on architectural or structural drawings. Another method used is to eliminate the "/" when writing fractions; 1/2 is written by placing the 1 over the 2 (which I can't do with the limitations of the program used by the "forum). However, I have attached a sketch that shows the differences between the systems commonly used. In each of the four examples shown, the interpretation of the dimension is the same.

Companies seem to have developed internal conventions for dimensioning their drawings that are not always the same as the company across the street from them. It can be confusing for all of us. We haven't even scratched the surface, consider geometric tolerance. Now you can get really confused.

Best regards - Al

Attachment: dimensions.dwg (25k)

Attachment: dimensions.wmf (13k)

By jrw159

Date 03-30-2008 18:09

OK, now I am following you. Bear with me I got lost for a minute.

By CHGuilford (****)

Date 03-29-2008 14:00

Speaking only for myself - I wouldn't care either way if the " is added to the fraction or not, as long as there is a dimension. If I see 1/4 or 1/4" I know one quarter of an inch is needed. If I see a 6 for a fillet size, then I look at other dimensions to assure myself I am dealing with metric.

One of my pet peeves is showing fillet dimensions on the arrow side but none on the other side. I have pointed out that we DO apply common sense when we see that but it often leads to questions that could be avoided - that it is NOT per A2.4. The response is often "Well that's what Autocad (or whatever)has in it's library and I'm not going to change it." So the drawing program is taking precedence over the specifications, and most detailers do not understand the difference.
I know it's a small 'thing' to some - as I said it is a pet peeve of mine.

By 803056

Date 03-29-2008 14:17

I agree with you on that issue Chet.

The designer that blames the problem on the computer program is taking the cowards way out.

The A2.4 standard for welding symbols haven't change that drastically since 1979 when the convention of dimensioning the weld on the arrow side separately from the weld on the other side was adopted. Likewise, I believe the system adopted for dimensioning groove welds changed about the same time. That's thirty years ago!

My experience is that about 85% of the drawings I see have welding symbol errors. The designer is responsible to make sure the information on the drawing is correct and complies with the conventions adopted by industry. Considering the fact that the designer usually has access to various reference books on the shelf above the computer monitor, there is no excuse for using incorrect welding and NDT symbols. It more likely a case where he or she is too lazy to get off their butt to look up the information.

I did a breakfast seminar last Tuesday for building officials, fabricators, and engineers. The first slide I presented was a symbol for a fillet weld on the arrow side of a joint. About 15% of the people in the group couldn't properly identify what side of the joint the weld was to be placed. I also made it a point to included a slide where a double fillet weld was properly dimensioned both above and below the reference line. I told the group that it has been required to include dimensions for both fillet welds since 1976.

We may be beating a dead horse, but what else can you do?

Best regards - Al

By eekpod

Date 03-29-2008 15:29

Anyone seen Spinal Tap????

"That says inches not feet!, Two marks means inches, one mark means feet, now Iv'e got a midget tripping over my Stonehenge" This is a classic example of the road crew building the wrong size stage prop and it's too small. It was supposed to be 24' not 24". anyway it's very funny.
But it points out a classic problem, things need to be clear. Especially for the end user who may not be an expert.

Our structural drawings are drawn with SDS-2 and they have both the foot ' symbol and the inch " symbol. It's very hard to get that wrong.

24' 2 1/2" = twenty four feet, two and one half inches.

Just my thoughts on a sunny sat AM
Chris

By 803056

Date 03-29-2008 16:03

Did I miss something?

I believe I did use ' for feet and " for inches.

Al

By DaveBoyer (*****)

Date 03-30-2008 05:02

Yes Chris, but can You turn Your wire feeder up to 11 ?

By eekpod

Date 03-30-2008 18:58

very nice :)

By jrw159

Date 03-31-2008 14:08

Proof positive that you can learn somthing new every day. I always thought, and I can not find any documentation to back it up, that if a fillet weld symbol has a weld size for arrow side and no size for the other side that the arrow side apply's. This was always referanced in the general welding notes so maybe that is where I got the idea that it is an acceptable practice. I guess I should review A2.4.

By mooseye (**)

Date 03-31-2008 14:50 Edited 03-31-2008 14:52

the ones I really don't like are those that will produce a drawing with measurements on one item in feet+inches and turn the page and the dimensions are in inches only. Talk about causing confusion and mistakes. This is especially true since most measuring tapes have inches and feet+inches described. 1-6 and 16 sometimes equal the same measurement, not.
And don't even get me started on metric.
We had a job for Mercedes-Benz that was dimensioned all in metric. Since most of the guys in the shop had no experience with metric dimensioning, hence no metric tape measure, the boss went out and bought all he could find. This consisted of one with millimeters, one with centimeters, one with standard and metric and another with millimeters and centimeters. What made it worse was that some guys would use a different one of these tapes during the day.
We had a large pile of scrap after that job.
And oh yeah, the PA had ordered the steel down to the inch. He wanted to know why we need to order more. ha ha

By rework Date 03-31-2008 15:37

Thanks for all the replies everyone...
Guess it basically doesnt matter all that much... which is a good thing.
Regards,
Chris R.