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Fillet Weld Size - Rule of Thumb

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Fillet Weld Size - Rule of Thumb

Fillet Weld Size - Rule of Thumb

swertel

(Mechanical)

(OP)

13 May 02 19:20

I recall somewhere that there is a rule-of-thumb for the size of fillet welds.  It is something along the lines of half the thickness of the thinnest member being welded.  Or was it twice the thickness of the thinnest member being welded?

Can anyone clarify this for me?

TIA,

--Scott

RE: Fillet Weld Size - Rule of Thumb

2

GRoberts

(Materials)

13 May 02 21:50

As with all rules-of thumb, there are a million exceptions, but the one you are probably looking for is that a double fillet weld, (of matching material strength) will be as strong as the base metal when the throat thickness is 1/2 the thickness of the thinner member.  This does not take into account stress risers, fatigue, etc, only strength of materials.

Further reading:
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RE: Fillet Weld Size - Rule of Thumb

3

pipewelder

(Industrial)

13 May 02 22:36

A reference is contained in Lincolns "Design Of Weldments" on Page 6.2-7. the paragraph states

"(a) for full strength welds, the leg of the fillet weld must be about 75% of the plate thickness."

Here is my take for double fillet welded joints

The effective throat of an equal leg fillet weld is .707 x leg size. .707 x .75t = about .53t. 2 equal leg fillet welds with leg sizes of 75% the thickness of the base metal would result in a fillet weld with an effective throat of 1.06t.

Good day

RE: Fillet Weld Size - Rule of Thumb

swertel

(Mechanical)

(OP)

14 May 02 09:50

Thanks all.

I'll look through Blodgett's (Lincoln Press') Design of Welded Structures again to verify this.  I figured this information was in there, but couldn't find it.

--Scott

RE: Fillet Weld Size - Rule of Thumb

atlarson

(Mechanical)

14 May 02 12:02

When a full strength welded joint isn't required, I use the following guideline.  These values are (mostly) from Bilichniansky's The Designers Manual.  It has been my experience that these size recommendations produce weldments that "look right" to most welders, engineers and managers.

Thinnest                     Fillet
Member                  Weld Size
----------------------
 1/8                            1/8
 3/16                          3/16
 1/4                            1/4
 3/8                            1/4
 1/2                            3/8
 5/8                            3/8
 3/4                            3/8
 7/8                            1/2
1                                1/2
1-1/4                          1/2
1-1/2                          3/4
2                                 3/4

RE: Fillet Weld Size - Rule of Thumb

apiguy

(Mechanical)

14 May 02 18:09
                         Table 5.8

   Base Metal Thickness                     Min. fillet size
       T= <1/4"                                 1/8"
       1/4"~1/2"                                3/16"
       <1/2"~3/4"                               1/4"
       3/4" plus                                5/16"
*** leg size need not be greater than the thinner of the two parts joined.

refer to 2.4.5 and find maximum fillet weld size...
   (1) for base materials 1/4" or less full plate thickness
   (2) 1/16" less than the base metal thickness, unless the weld is designated to be built out to obtain full throat thickness.

hope this helps....

According D1.1 the following minimum sizes apply:Table 5.8Base Metal Thickness Min. fillet sizeT= <1/4" 1/8"1/4"~1/2" 3/16"<1/2"~3/4" 1/4"3/4" plus 5/16"*** leg size need not be greater than the thinner of the two parts joined.refer to 2.4.5 and find maximum fillet weld size...(1) for base materials 1/4" or less full plate thickness(2) 1/16" less than the base metal thickness, unless the weld is designated to be built out to obtain full throat thickness.hope this helps....

Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico

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News

By

Date

07-02- 04:27

Edited

07-02- 21:17

07-02- 04:-02- 21:17

You need to consider the welding process when using table 3.7.

Consider the single pass vertical fillet weld made with SMAW. A 1/2 inch fillet leg translates into a face dimension larger than 5/8 of an inch. There goe the 3X the rod diameter restriction for low hydrogen electrodes. There are no restrictions on the width of the second layer, third layer, etc., for SMAW.

It is doubtful that the restictions of depth versus width limitations imposed would be  concern with SMAW. It would most likely be a concern with SAW.

Now, if notch toughness is an issue, I would be concerned with the width of the layers because of the implications on travel speed and heat input.

Best regards - Al

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