Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Register Login
Up Topic Welding Industry / Welding Fundamentals / Soapstone Trick
- - By Cumminsguy71 (*****) Date 05-01-2015 02:36
I know that a lot of you probably know this trick but I was taught the other day by an awesome inspector, one of the cool ones, a little trick.

Flat soapstone, about a quarter inch on the thin side and the wide side is 1/2".

If you're doing a fillet weld, say a 1/4" take your soapstone, wide side and put it in the corner, drag it down. You will have two lines with the root in the center. If you weld to the lines you will have a 1/4" fillet weld. Maybe you need a 5/16" fillet instead. Consume the lines on either side and you will have a 5/16" fillet weld.

Not a high tech trick but after 8 years I never heard of this. A good little trick if you don't have fillet weld gauges handy.

Parent - - By aevald (*****) Date 05-01-2015 03:16
Actually Shawn, that's a great "trick", thanks for sharing. I hadn't come across that one yet and I'm sure that some of our students will certainly benefit from it, especially when they have a hard enough time just running a bead, let alone a correctly sized one. Thanks again and regards, Allan
Parent - By Cumminsguy71 (*****) Date 05-01-2015 11:29
That's why I wanted to share that tidbit Allan, passing along the knowledge! LoL!

A 5/16 weld in actuality is not a 5/16" weld, more like a 7/16" to 1/2" weld depending on how you look at it. Explain that to the kiddies in class because if you use a tape measure you will be wrong. :grin: Pythagorean Theorem comes into play on this one.

Why do they even mark the fillet gauges 5/16 when measured across the gauge is obviously not? Weld depth now, 5/16. Must be some sort of engineering logic behind this.
- - By welderbrent (*****) Date 05-02-2015 00:15 Edited 05-02-2015 00:19
FIRST, the bad news.  Soapstone is 3/16" X 1/2".  Not even close to 1/4" thick especially when using it for a guide for sizing welds.

Now, come on Shawn.  When a fillet weld is called for 1/4" that is the leg length which is exactly what you are trying to assure with your tip.  Any other measurement is up to the engineer.  He has calculated it for effective throat then adjusted it to leg length to make it simple for us non educated welders and inspectors.  

We are in no way interested in the dimension through the throat and especially not across the face.  Either of which can be calculated with 3/4/5 or Pythagorean Theorem. 

How can you accurately use a tape measure anyway but if I did, why wouldn't I get the right leg length? 

I'm having trouble with your argument Shawn, a 5/16" fillet weld is exactly that.  5/16 on each leg.  That is how it is called out according to every book out there.  The throat is actually only about 70% the length of the leg.  So it is shorter, not longer than the 5/16" or about 3/16".  Now, across the face would be a longer dimension (about 35% longer) but I don't see how that comes into play at all.  The face dimension isn't used for anything.  Totally useless number for strength of weld or size of weld.  The only thing that interests us about the face is the contour and the compliance with Table 6.1 and weld profile samples. 

Only thing coming to mind here is the concave gauge instead of the convex gauge.  Even then, one has to know all the ways that is calculated which does mean you are measuring the throat, about 20% of fillet welds may use this gauge.  And you would be correct, the throat will not be 5/16" if using my current example.  It will be about 3/16".  Smaller than the 5/16", not larger.  And it is possible to make the legs of a 5/16" concave fillet equal about 1/2" or even more.  But, in a concave fillet, the legs are of no consideration just as the throat is not of any consideration to the inspector when checking a convex fillet weld. 

Did I miss something?  Because I am just not seeing the topic as you appear to have expressed it.

BTW, FYI, look up posts by Al Moore explaining the measuring and use of fillet weld gauges for these welds.  I'll see if I can attach some of his illustrations. 

Using the image I attached, the white triangle would be our 5/16" fillet weld.  The legs must be at least 5/16".  The throat is less.  Even if it is a concave fillet weld. 

He Is In Control, Have a Great Day,  Brent
Parent - By 803056 (*****) Date 05-07-2015 19:58
Thanks for the credit Brent.

Best regards - Al
Parent - - By Cumminsguy71 (*****) Date 05-31-2015 14:25 Edited 05-31-2015 14:33
Maybe the soapstone I have is 1/4", know I measured it after the inspector that told me about this trick. Didn't put micrometers on it cause as Grandpa always said, "ain't building a church".

I assumed many years ago I guess, 5/16 was across the face of the weld but in what I do when they call out the 5/16" it is easier at times to run three stringers due to severe gaps between the new steel and existing steel. First pass is a fill, other two give the depth and width required.

I've used the soapstone on a joint, marked it and measured with the gauges and if I consume the lines on either side then I would have a 5/16" fillet weld as specified by the EOR.

A 5/16" weld is 5/16" on each leg, across the face it is not. That was my point. How to measure across the face with a tape measure, relatively easy actually. Perhaps my education at the state tech school wasn't very good on these particular things but considering 8 years ago I was a super technician in the auto and heavy equipment world with no prior welding experience or education I still have more to learn and claims of being a super welder have never left my mouth. I'm a humble doing my best welder and if inspectors and clients sing my praises so be it, in one ear out the other for me.

The throat of the weld isn't even my concern really as long as it is not to convex or concave, personally I go for the perfect 45, smooth across the face, not bulging out or sunk in like a 90 year mans cheeks. As long as I am within the guidelines of what is called out in AWS then I'm happy.

"FIRST, the bad news.  Soapstone is 3/16" X 1/2".  Not even close to 1/4" thick especially when using it for a guide for sizing welds."

If the soapstone is 3/16" then that would be a non issue as that is not even a measurement used in the soapstone trick. The width across the wide side is what is being used for your mark. Be it 3/16, 1/4 or 6 inches it's still the 1/2" you will be using as the guide to size your weld.

"How can you accurately use a tape measure anyway but if I did, why wouldn't I get the right leg length?"

Measuring across the face with a tape measure, which I know now is of no concern but in actuality it is. You can't make a 5/16" fillet weld, a 1/4" fillet weld, etcetera without the correct size across the face.

5/16" leg and another 5/16" leg on a triangle.

.3125 x .3125 = .09765625 + .09765625 = .1953125. Square root of that is .4419417 which is, 7/16" across the face which is not 5/16". That was the point I was making. Make a 7/16" weld as measured across the face or as is the width of the fillet gauge on the diagonal and that would be a 5/16" weld if you could measure the legs somehow.

Knowing this sort of stuff and the tape measure I typically have in my tool belt that cost $10 is safer than carrying the $30 fillet weld gauges when it comes to "oops, there they go" type of incidents. Already lost one set of gauges when they were "borrowed" to take pictures. Knowing the face and I don't need gauges. 3/8 fillet, then put in the appropriate weld size as measured across the face and I'll have a 3/8" weld on the legs just because of geometry.

The original topic was using the 1/2" wide soapstone as a guide for 1/4" and 5/16" fillet welds so my original post is spot on with the explanation. My tangent in my second post where I said a 5/16" weld is not a 5/16" weld, depending on how you look at it or point of view is where the thread skewed. 

Parent - By fschweighardt (***) Date 06-01-2015 17:51
If you have a nice flat weld that makes a nice right triangle in a 90 degree tee joint, and it is 1/2" across the face, the legs (fillet weld size) will be about  .3535

this is the result of 1/2" x .707 (sqrt2) = .3535" or about 11/32", which is not so far from 5/16"
Parent - By dick (**) Date 06-02-2015 02:34
Shawn, I use this several times each week in the aid to help young welders. It gives them something to shoot for in differant weld sizes.
Good trick!
Yes I use Fred's easy point also. Sweet!

Parent - - By welderbrent (*****) Date 06-02-2015 03:11

Sorry, I had the wrong view of how you were using the soapstone.  Realized after reading this post and re-reading the first one that I had misunderstood. 

But, as you mark and the edge of the soapstone wears down, won't the fillet get smaller and smaller as the soapstone fits down into the 'V' more?

Still not sure I understand how you are using the tape measure but if you have something that works for you, great.  It's all about getting yourself set up so you get the proper sized welds so the inspector doesn't ding you to fix a bunch of undersized welds.  Especially ones that are 500' in the air :eek: .

Won't bother to muddy the waters with how I thought you were using the soapstone to mark the edge.  But, I still think you will find that soapstone is only 3/16" and I didn't use a mic either  :lol: .

Just for clarification, I was not and would not challenge your skills as a welder.  I misunderstood how you were using the soapstone and still don't understand what you are doing with the tape measure.  Maybe you could post a pic for this old man.  I always did do better reading the picture books.  But your skills were not to be challenged and I know you don't make more of yourself than you are.  You are probably better than you realize.  Just don't let it go to your head. 

To explain myself some and show you a variation of this, while I was teaching my boys to weld I cut them a short piece of 5/16" square bar and had them mark down both sides of it in the 'T'/'V' of the joint for the fillet weld.  That gave them lines that were the size they wanted the legs to come to. (I thought you were laying the soapstone down flat and using a second one down the face to mark the leg for the fillet weld.  And, whichever thickness soapstone you have, would have been shy of 5/16" by either 1/16 or 1/8).

Parent - By Golden Arm (*) Date 08-13-2015 19:18
The lessening of the leg lengths. That was my first thought. I remember a BC cartoon several years ago. A guy walking along the beach dragging a forked stick behind him in the sand. Eventually the stick wore down and lines ran together and he said something to the effect that parallel lines do eventually meet.
Up Topic Welding Industry / Welding Fundamentals / Soapstone Trick

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill