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Up Topic Welding Industry / Technical Discussions / Weld symbol Question
- - By jwright650 (*****) Date 12-14-2005 14:10
I have a groove weld symbol with a square(not rectangular) box on the opposite side, but the box has an "M" in it, what does the "M" stand for?

1)Is it a type of consumable insert that is being specified?

2)Is it mis-drawn and should indicate backing, but they intend for the backing to be removed?
John Wright
Parent - - By jon20013 (*****) Date 12-14-2005 15:17
John; in looking at A2.4, a SQUARE box would seem to indicate a consumable insert. I've never heard of an "M" type consumable insert however. If I were to speculate it sounds like the drawing might be indicating "M" for machining as in machining a backing bar away after use. Sorry I can't give you a better answer but there's my two cents!
Parent - - By tito (**) Date 12-14-2005 16:12
If the backing bar (rectangle) or the consumable insert (square) where to me machined, shouldn't there be a contour symbol (flat line) above the square or rectangle, and then the "M" above that? That's just what I thought it should look like. Could be wrong though.

Let us know when you find out.

Parent - By gsi (**) Date 12-14-2005 16:21
What we have seen in the past is the "M" is a non-standard term , in the world of engineers for METAL
Parent - - By gsi (**) Date 12-14-2005 16:22
However what other typs of consumable inserts are there ?
Parent - - By CHGuilford (****) Date 12-14-2005 17:20
John,
I know you must have looked at AWS A2.4 so I won't bother to look at mine. The last time I saw a symbol as you have described, the "M" meant metal backing. It usually means a metal that is weldable to the base metal, as opposed to using copper or aluminum for backing on steel welds.
We don't see that much any more because the welding codes pretty well describe what the backing material can be. Today, we either use a steel backing, backgouge, or use a non-fusing backing and backgouge the weld.
That symbol does not indicate whether to remove backing or not, to the best of my knowledge.


gsi,
I don't know of any consumable inserts in use that are not compatible with the base metal.

Chet
Parent - By swnorris (****) Date 12-14-2005 18:05
John,
I haven't seen it in a long time, but the square box indicates backing, and the M inside the square box indicates material as specified. It could be any type of qualified backing. If the backing is to be removed, the M is replaced with MR in the square box. Technically, the box is supposed to be rectangular, but you know how detailers are.........
Parent - By bmaas1 (***) Date 12-14-2005 18:14
John

In my opinion it would be an insert as drawn if it is square and not rectangle and to be machined after. If it is an insert the type should be stated as well. I would check with the detailer.

Brian
Parent - - By jwright650 (*****) Date 12-14-2005 18:19
This symbol was shown on the Engineer's drawings so, if the question still plagues our people here after I print out all of the forum responses, I will fire off an RFI to clear it up.
Thanks for all of the replies thus far,
John Wright
Parent - - By swnorris (****) Date 12-14-2005 18:35
John,

I don't know if the M and MR are part of the standard welding symbols anymore, because I don't have a current A2.4. As I said, it's been a long time since I saw it used. The only A2.4 I have is from 1979, and it shows the meaning of the M and MR. If they aren't shown in the current publication, I can scan the one I have and email it to you if you need it.
Parent - - By jwright650 (*****) Date 12-14-2005 18:38
If you don't mind....scan it and email. I'd like to have it for my files if nothing else. No, the A2.4 I have is a 98 and it is out of date now, there is a newer one out that I need for our AISC library collection. I figured I would order it when I order our new 2006 D1.1s.
John Wright
Parent - - By swnorris (****) Date 12-14-2005 19:31
jon20013,

Again, I don't have the current A2.4, so I don't know whether it's been changed, but the M you referred to in your post is to be shown outside the rectangle, not inside it. But, as you stated, it does indicate machining, and is used primarily for plug and slot welds. Also, a joint with a spacer, which I think Brian was referring to as an insert, is designated with, or used to be designated with an M inside a rectangular box as well, but the two different scenarios were/are easily distinguishable because of the differences in the two welding symbols.
I have a couple old A2.4's, one from 1979 and one from 1986 that I refer to from time to time. Keeping those old publications comes in handy sometimes.
Parent - By jon20013 (*****) Date 12-14-2005 19:58
Scott, you are correct. I am looking in a 1993 issue of A2.4 (not exactly current!) and there isn't a lot in it regarding consumable inserts, just has the square and some verbiage at para. 4.8 showing tail information as to the Class of Insert. After reading all the other posts, its my best guess the square was really meant to be a rectangle (as a backing bar). I also remember in yester-year when "M" indicated metal but don't believe that terminology is still with us. Likewise, just a guess but the original draftsperson may have intended the "M" to be outside the box....
Up Topic Welding Industry / Technical Discussions / Weld symbol Question

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