rules of thumb

By thermotek Date 11-10-2004 01:54

I have been searching for a rule of thumb to guide me in determining the correct size for a fillet weld when the fillet symbol is used without a size specification.
I would most appreciate a copy and paste response from a welding reference publication that is succinct and precise.
I suspect that most of the operators where I work are applying WAYYY to much bead on most of their joints.
Typically, they will apply a fillet weld that is .38" to join two pieces of 14ga. CRZC.
I don't think that the engineers had this in mind when they specified the weld, but I need to have documentation to back that up.
Regards,
Mark W.

By pipewelder_1999 (****)

Date 11-10-2004 03:19

For the effective throat of a double fillet welded joint to be equal to the base metal thickness, each weld should be about 3/4 of the material thickness.
See this http://www.weldinginspectionsvcs.com/relationship_of_fillet_weld_size.htm

That does not address the proper use of the fillet weld symbol. Somewhere the size should be specified.

Doubling the fillet weld size increases the abount of weld by a factor of 4.

Have a nice day

Gerald Austin

By TimGary (****)

Date 11-10-2004 12:35

If you are making welds in accordance with the AWS D1.1 code, then the minimum fillet weld sizes are detailed in Table 5.8. Based on this table, a good rule of thumb would be that the ideal fillet weld size equals half of the thickness of the thinner part joined. This way, you will be at or just above the minimum size acceptable for the required strength of the joint without overstressing the material or wasting time and filler metal.

Tim

By swnorris (****)

Date 11-10-2004 17:25

Hi thermotek,

In addition to what Tim mentions, on the other end of the spectrum, per the AISC, the maximum size of fillet welds that is permitted along edges of connected parts is as follows:
Material less than 1/4" thick, the weld size is not greater than the thickness of the material.
Material 1/4" or more in thickness, the weld size is not greater than the thickness of the material minus 1/16", unless the weld is especially designated on the drawings to be built out to obtain full throat thickness.
The minimum weld size is dependent on the thicker of the two parts joined, except that the weld size need not exceed the thickness of the thinner part. Weld sizes larger than the thinner part joined are permitted if required by calculated strength.

By pipewelder_1999 (****)

Date 11-10-2004 17:50

I would siggest contacting theparties responsible for the engineering and request clarification of what is required. General notes and sometime individual project specification will clarify items that are not "noted otherwise".

Have a nice day

Gerald Austin