Fillet Weld Gauges

By jwright650 (*****)

Date 08-16-2010 18:52

Like this one?

By welderbrent (*****)

Date 08-16-2010 19:24

Chris,

I think you have to break that question down into two separate answers:

1) For the end of the gauge measuring Concave Fillet Welds, the end with a double curve relief, it would be the Theoretical Throat as it does not take into account or consideration the penetration of the weld in the root. If it did take the root into account then it would be both the Actual and the Effective Throats as defined by A3.0 and illustrated in A3.0 on p.83 Figure 25, A-D. They are the same in Concave Fillet Welds.

2) For the end of the gauge measuring Convex Fillet Welds, the end with the single curve relief, it would be none of the above. That measures the leg length which is how the majority of Fillet Welds are called out and while it is directly porportionate to the throat it is not any of those by definition though it would be mathimatically.

Have a Great Day, Brent

By jwright650 (*****)

Date 08-16-2010 19:36

Along with what has already been posted...the blade type gage won't give you actual or theoretical throat dimns because it doesn't take into consideration fillets with unequal legs nor can it assume that both leags are equal...the cam gage on the other hand does.

By Lawrence (*****)

Date 08-16-2010 19:45

I think it is a terminology thing.

Weld size measured via blade tools is a product of gauging leg length....

We are not talking about the various variaties of "throats" here so much..

Is each leg length sufficiant? go or no-go

By eekpod

Date 08-17-2010 10:27

Thanks for the input guys, I got an e-mail back from G.A.L gage company and they said the blade type gauges measure "theoretical" throat.

I guess I always assumed it was actual throat, since that is was I actually have in front of me.
So when I use my Bridge Cam Gauge I need to use the "actual" side of the throat scale and make sure no-one tinkered with it and reversed it to the theoretical side or my sizes will be off.

Chris

By welderbrent (*****)

Date 08-17-2010 14:16

Chris,

Personally, I would use the Theoritical measurements. You can not know, only estimate, the depth of root to come up with the actual and/or effective throat meausrements unless you are able to cut and etch a weld coupon. The same goes for the bridge cam. It is only an estimate of what COULD be the actual throat.

But for a welder who has used a particular process successfully in the past, you are pretty safe to say his weld is at least as deep as the theoritical root of the joint.

At the base of the question though would be rather this is for a particular job with specs that would call out the weld to be done to a specified measurement and then how it is to be inspected. Which scale of measuring you use depends upon how the engineer specified the size of the weld in the first place. Then you MUST use the proper tool with the appropriate scale to verify that the welder deposited the weld to the correct size. In my work, mainly D1.1 structural, almost all fillet welds are called out per leg size. And while John was correct in his above statement, even unequal size leg fillets can be easily checked with the blade fillet gages to make sure both legs are of the correct size. I have seldom had occassion to measure the throat of the weld. I have on occassion had to show welders the difference and show them the notes and/or code that make the leg measurement the critical factor, not the depth of throat. And on long runs of fillet weld it is much easier, IMHO, to measure with the blade than with the Bridge Cam rather I use it on the leg or the throat.

Just my two tin pennies worth.

Have a Great Day, Brent

By jwright650 (*****)

Date 08-17-2010 14:34

Reason I mentioned unequal leg sizes.....that messes up the throat dimns.....an extreme example: 1/8 x 5/16 fillet is not going to have much of a throat dimn. That is hard to determine from a blade style fillet weld gage without doing some math to know what to expect at the throat.

By welderbrent (*****)

Date 08-17-2010 14:40

Very true John and I wasn't being critical of what you said, only using it as an example. But thanks for that followup info.

Have a Great Day, Brent

By jwright650 (*****)

Date 08-17-2010 14:47

No worries, just clarifying my broad statement a bit for those who may not have caught what I was getting at.

By eekpod

Date 08-17-2010 19:13

well, maybe I'm doing something wrong then.
I use the either the blade or the bridge cam gauge to measure the legs, to make sure they meet whatever size is called out for on the drawings. I have not had a particular job call out anything specific like "theoretical". I make sure we have the minimum leg size.
But to make sure I have enough throat, I also use the gauge to make sure I have the minimum throat dimension. I find it easier to use the blade gauges than the bridge cam gauge.
Question; so should I not be checking the throat? If the drawing says 5/16"fillet weld only check the legs?
I check both on occasion to make sure my newer welders are putting in enough meat (Throat in this case) on their welds. Also I tell them not to make concave fillet welds, to reduce/ eliminate not enough throat situations. They should be "flat" or convex, but to stay away from concave unless noted on the drawing (which I have never seen).

This is how I originally got into this issue, I compared my bridge cam throat to my blade type throat and found a difference, then I got into the theoretical vs actual and realized their were two sides to the bridge cam throat gauge. Maybe I noticed this years ago and forgot, who knows but it woke me up.
Chris

By jwright650 (*****)

Date 08-17-2010 20:05

Chris,
If the leg sizes are what is called out, and if the fillet is concave, use the blade for concave fillets and make sure the middle touches.....that verifies that the min. throat.

If the middle of that gage does not touch, the welder will have to add more filler for that fillet to pass visual inspection.

By welderbrent (*****)

Date 08-19-2010 16:11 Edited 08-19-2010 16:13

Chris,

I had to run a little experiment and then I keep getting interrupted trying to get back to this.

1) I would, for the most part, only check the leg size it the drwg is calling for 5/16" fillet welds and they are convex. But, I said for the most part, if the weld looks flat or is DEFINITELY concave then I double check with the concave end of the blade gage.

2) Now as to your trying to see how the blade compares to which throat- actual or theoretical, I ran some various sized fillet welds and ran some tests. My personal opinion is that when I compare a weld of ANY size with the concave blade gage it matches the bridge cam's 'Theoretical' scale throat gage. The 'Actual' scale would require even more weld. Not necessarily bad. Especially with this consideration:

D1.1:2008, Clause 2.2.4 (1) States- "For fillet welds between parts with surfaces meeting at an angle between 80* and 100*, contract documents shall specify weld leg size."

From the 3.0 definition of a Fillet Weld and all applicable references it must be at least flat, and preferrably slightly convex, across the face to be the 'triangle' with the called out leg measurement.

From this I note: a) a 5/16" Fillet weld with a slightly convex surface will meet all requirements when examined with a blade Fillet Weld Gage for convex welds; b) when double checking the throat with the 5/16" concave blade it is really large enough, not even a question; c) When checking a Fillet Weld with the correct leg size BUT with a concave face the 5/16" concave blade will not touch; d) By the time the weld is large enough to touch with the 'Theoretical' throat Cam gage or the concave gage of the blade gage it will be about twice the leg measurement as was called out; e) when using the 'Actual' scale it would be even larger because even more throat is required to touch the point of the gage to get your measurement;

Thus: If I use the 'Theoretical' to measure a concave fillet, then compare it to the 'Actual' I can have a fair APPROXIMATION of the true size of the fillet weld including penetration. But, unless a concave fillet is called out, the most accurate and only meaningful measurement is rather the leg length is Acceptable and the face is at least flat so that the enclosed triangle is of the size required by the engineer in the contract documents/prints.

Do this, take a piece of paper, draw a 'T' joint, take your blade gage for any size weld, trace around the convex end, now trace in the same area around the concave end. Is the 1/2" concave fillet going to give you anywhere close to the right weld for a 1/2" convex/leg length fillet? A 3/4" concave fillet is just enough weld for a 1/2" convex weld. And that's equal to about a 7/8" leg. That's a lot of difference. Then if you go by the 'Actual' scale you would have them adding even more.

Bottom line, not sure why you would double check a true convex fillet with ANY concave scale gage. Don't think it really accomplishes the proper or desired end result and it doesn't really matter rather you use 'Actual' or 'Theoretical'.

Think I drug this out enough. Hope I made sense. Just my two tin pennies worth.

Have a Great Day, Brent

By eekpod

Date 08-19-2010 19:46

wow, thanks for all that effort and information. Tomorrow when I have time I'll try your little experiment.
Chris

By CWI555

Date 08-18-2010 00:03

gal gages video
Boring as hell but some good information.
http://www.youtube.com/watch?v=vzYj0qsLbVY&feature=player_embedded#!

By eekpod

Date 08-19-2010 19:56 Edited 08-19-2010 19:59

Interesting, the video says "the actual throat dimension" is measured, not theoretical.
Your right, dry and boring, but to the point, they need to pick up the pace and it woulnd't be too bad.

Also, I am mainly concerned with this issue with multi-pass fillet welds, that's why I check it to make sure they have enough.