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> How to measure a fillet weld
rotten_root
post Feb 23 2011, 07:27 PM
Joined: 19-Jan 08



Hi all,
Got into a discussion about fillet welds today and how to measure / weld them. The way I was trained was that if you were joining let’s say a 10mm plate to a 6mm plate in a " T " joint then this would require a 6mm fillet. 6mm being your throat thickness and then dividing your throat by 0.7 to give leg length which is in this case 8.6mm which would be deposited with three runs with 3.2mm electrodes. The “old skool “welder says this is nonsense and your fillet size is measured by leg length only. Help me out.

RR
Boilerbuster
post Feb 23 2011, 09:01 PM
Joined: 23-Aug 08



Leg length is "Old Skool", lol!!!
skaginn
post Feb 23 2011, 09:02 PM
Joined: 11-Mar 07




How it is measured depends how it is written on the weld spec or the relevant drawing.

JC
rotten_root
post Feb 23 2011, 09:11 PM
Joined: 19-Jan 08



well i was on the twi site and they say when its british its leg length and when its europe its throat!
but a 6mm leg is only going to give a 4 mm throat. Is this enough? its an asme 1x spec
cheesed off
post Feb 23 2011, 10:14 PM
Joined: 30-Jan 10



I wouldn't like to bump into you in the local boozer if that's your topic of conversation. Simply ask the gaffer what fillets size he wants, then blame him if its wrong. laugh.gif
douglas
post Feb 23 2011, 10:47 PM
Joined: 21-Jun 08



Looks like the TWI are anti EU too, guess they must have copies of the daily mail in the waiting room.

Get away with as much as you can is the best and most common ambition in my experience.

doug
try_some_welding
post Feb 23 2011, 11:30 PM
Joined: 14-Jan 07



QUOTE (rotten_root @ Feb 23 2011, 07:27 PM) *
... require a 6mm fillet. 6mm being your throat thickness and then dividing your throat by 0.7 to give leg length which is in this case 8.6mm ...


Hi rotten root

For any fillet with equal leg-lengths what you say is always correct.
That is "God's design" and anyone disputing it can take their "Standards" or other "word of man" and shove it where the sun don't shine biggrin.gif

This has been known for at least 2500 years and is demonstrated by the principle of Pythagoras.
Your "0.7" is "1 over square root of two".

So multiplying the throat thickness by square root of 2 gets you the leg-length.

If you wanted to know, look it up on the Internet.
This is the maths without explanation -
a^2+b^2=c^2
if a=b the 2a^2=c^2
therefore
c=(square-root-2)a

Some of the ideas you are working with about the relations between plate thickness and other dimensions - throat and fillet-face - are shown at the bottom of this page
http://www.weldsmith.co.uk/tech/welding/le...let_leglen.html

Try Some
Technic Al
post Feb 24 2011, 12:11 AM
Joined: 14-Oct 03



does weld shape play a part

measuring "a" or leg legth of a convex or concave fillet could produce very different weld strengths
try_some_welding
post Feb 24 2011, 08:16 AM
Joined: 14-Jan 07



QUOTE (Technic Al @ Feb 24 2011, 12:11 AM) *
does weld shape play a part
measuring "a" or leg legth of a convex or concave fillet could produce very different weld strengths

Thanks for being polite in introducing that! These things about "square root of 2" apply to a straight-sided 45deg-45deg-90deg triangle. It's being engineering-minded analysing these things - going from theoretical triangles to real weld shapes and how you economically get a weld that is "good enough".
Captain
post Feb 24 2011, 09:49 AM
Joined: 18-Nov 03



Hi lads,
I am from the "Old School" and I was always told that the fillet size was determined by the leg length.

Digressing a tad, but as I'm an "old schooler" (dinosaur maybe?), I still at times refer to rod sizes in the old S.W.G. (standard wire guage) size!!!-
2.5mm as 12's, 3.2mm as 10's, 4mm as 8's, 5mm as 6's. And it is a long long time since I have came across the old 1/4's - 6mm.

biggrin.gif

Captain
Technic Al
post Feb 24 2011, 11:10 AM
Joined: 14-Oct 03



Being pedantic 1/4's should 6.3mm and 6 guage should be 4.8mm (or was that US sizing) so to cater for everyone we used to make the lot
4.8, 5.0, 6.0, 6.3 and even 7.0, 8.0 and 10mm. The 10mm stainless were beasts, used for welding Centurion Tanks.

4.5mm and 5.6mm also cropped up occasionally

6mm are very rare these days. Replaced by MIG.

In an attempt to keep on topic. We used to produce an electrode sized by fillet size. So instead of 4mm or 5mm it was called "a4", "a5", "a6" etc which were the throat thicknesses produced if the weld length was 900mm (they were the 600mm long electrodes). That used to cause some confusion with the Inspectors on their WPSs. I had many a long conversation about that one.
Captain
post Feb 24 2011, 01:52 PM
Joined: 18-Nov 03



Thanks Al,
yes, I did realise that the mm to the old SWG sizes I quoted were not exact, but a generalisation of sizes we used amongst the old schoolers, and they would be as near as we could get.
I also remember using a 5.6mm rod when I worked in West Germany in the early 80's. It was a beast to use, and it was for stoving down overs on ships frames. The sparks & fumes were horrendous.

Captain blush.gif
Technic Al
post Feb 24 2011, 03:37 PM
Joined: 14-Oct 03



I wasnt putting you right, just commenting

Those stoving rods, wasnt Blohm & Voss Hamburg was it. If so, we made them, but the memory is failing me. I cant recall what they were called. Might have been NV26 or NB26
Captain
post Feb 24 2011, 03:42 PM
Joined: 18-Nov 03



Hi Al,
no problem.
The yards I used them were indeed Blohm & Voss in Hamburg, and I also used them in Rickmers Verft in Bremerhaven. Oh happy days! rolleyes.gif
Can't remember the name of the rods though, like your good self, the memory aint what it used to be.

Herr Capitan
chopout
post Feb 25 2011, 05:50 PM
Joined: 24-Jan 06



QUOTE (Technic Al @ Feb 24 2011, 11:10 AM) *
Being pedantic 1/4's should 6.3mm and 6 guage should be 4.8mm (or was that US sizing) so to cater for everyone we used to make the lot
4.8, 5.0, 6.0, 6.3 and even 7.0, 8.0 and 10mm. The 10mm stainless were beasts, used for welding Centurion Tanks.

4.5mm and 5.6mm also cropped up occasionally

6mm are very rare these days. Replaced by MIG.

In an attempt to keep on topic. We used to produce an electrode sized by fillet size. So instead of 4mm or 5mm it was called "a4", "a5", "a6" etc which were the throat thicknesses produced if the weld length was 900mm (they were the 600mm long electrodes). That used to cause some confusion with the Inspectors on their WPSs. I had many a long conversation about that one.



QUOTE (Captain @ Feb 24 2011, 01:52 PM) *
Thanks Al,
yes, I did realise that the mm to the old SWG sizes I quoted were not exact, but a generalisation of sizes we used amongst the old schoolers, and they would be as near as we could get.
I also remember using a 5.6mm rod when I worked in West Germany in the early 80's. It was a beast to use, and it was for stoving down overs on ships frames. The sparks & fumes were horrendous.

Captain blush.gif

Just been useing 4.5 rods Lincon Ferrod 165a 600 long Its a 7024 iron powder not seen them before ohmy.gif
Technic Al
post Feb 25 2011, 07:34 PM
Joined: 14-Oct 03



chopout

Really....Ferrod 165A...............I developed that product quite a few years ago now. We made the 4.5mm for one customer who wanted a specific fillet size using them on a Gravity Feeder (Ski). I cant remember who it was or what size they wanted.

I thought they had stopped making them . I think they are probably old stock.
chopout
post Feb 26 2011, 09:07 AM
Joined: 24-Jan 06



Yes sounds about right the box's have no polethene cover.
Our firm will by anything if its cheap blush.gif blush.gif
Not a bad rod though. Make a good Firecracker rod
philbird
post Feb 28 2011, 02:33 PM
Joined: 4-Feb 11



hi all

hope this is of some help:-
according to CSWIP
minimum leg length size is the plate thickness
maximum leg length size is the plate thickness + 3mm
minimum throat thickness is the plate thickness x 0.7
maximum throat thickness is the plate thickness + 0.5mm
LT welder
post Feb 28 2011, 11:02 PM
Joined: 28-Feb 11



Hi Philbird, This does not sound right to me (unless its general rule of the thumb stuff)

The weld size depends on the required strength although plate thickness is a limitation on overall weld size. e.g not advisable to put a 15mm leg length fillet on 6mm plate.

I have work on loads of structural jobs that ask for 6mm leg fillets on 8mm plate and also 8mm leg length on 10 or 12mm plate. There are suitbale for single passes with stick, MIG or flux cored (depending on filler diameter).

Therefore min leg can't be equal to plate t. (think of thick section like 40mm plate, that would be a big fillet, although a butt joint configuration would probably be used)
philbird
post Mar 1 2011, 12:27 PM
Joined: 4-Feb 11



hi L T WELDER
i think it is a rule of thumb as the information that i suplied was quoted from cswip 3.0 visual welding inspector documentation, it was an example taken from the acceptance sheet based on a 6mm fillet weld on 6mm plate. i can understand why it does not sound right as i also come from a structural background and most dimentions are stated on the drawings/wps, and 9 times out of 10 they say all fillet welds to be 6mm unless otherwise stated.
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