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Thumb rule for fillet size

Thumb rule for fillet size

(OP)
Dear sir,

What will be the thumb rule for fillet size, if two different thickness has to be weld.

It may be given in AWS D1.1, but I want to know basic rule.

For example : I want to weld 32mm thick plate with 50mm thick plate., Then what will be the fillet size.

Pls help and guide me.

Regards
Prasad

RE: Thumb rule for fillet size

Hi Prasad,

The minimum fillet weld size, as shown in AWS D1.1 (2015) Table 5.7 as a function of base metal thickness has this note under MINIMUM SIZE OF FILLET WELD:

"(b) except that the weld size not exceed the thickness of the thinner part joined"

In your case, the minimum fillet weld size would be 8 mm, although you may want to go larger depending upon fitup, etc. to achieve an acceptable weld profile (See Figure 5.4).

RE: Thumb rule for fillet size

(OP)
Dear sir,

Thanks for response.

For 32mm and 50mm the plate, 8mm welding will be a minimum welding size.

I know welding itself is bad, as it leads to distortion and stress in material.

Only want know, what will be the maximum size, we would recommend to weld.

Pls help.

Regards
Prasad

RE: Thumb rule for fillet size


With the belief that you are using a prequalified joint, take a look at AWS D1.1 Table 3.6 for your specific application. If not, you can still use the information provided as your engineering rationle.

RE: Thumb rule for fillet size

32 mm plate to a 50 mm plate? Why would the minimum fillet be 8 mm?
Maximum for strength transfer is 32 mm, beyond that the weld is stronger (and thicker) than the plate, and so extra fillet weld material does not contribute to the joint strength. On the other hand, a v-prop for the 32 mm plate could all more useful joint area.

RE: Thumb rule for fillet size

If you are welding a T-joint using low carbon steel or a high strength low alloy steel using a matching filler metal, a double fillet weld (a weld on each side of the butting member), equal to 3/4 the thickness of the thinner member, you will have developed the full strength of the thinner member in both shear and tension.

Best regards - Al

RE: Thumb rule for fillet size

(OP)
Dear sir,

Thanks for your reply from nuclear and structural specially.

Sir, I only want to know that 3/4 i.e. 0.75 * minimum thickness (thinner part)will be consider as a basic thumb rule.

Or is any formula is there. (it is seems to be a good ) any logic behind considering of 0.75mm figure.

Pls help.

Regards
Prasad

RE: Thumb rule for fillet size

Again. Get your dimensions correct: 0.75 mm is NOT .75% of the minimum plate thickness. You owe yourself, your clients and your client's customer clear, unambiguous values and designs!

But, assuming you mean 75% of the thinner plate for two plates welded with two fillet welds in a T-shape, then you need to clarify if you are assuming the "Euro" convention" of designating fillet welds by the throat dimension of the weld?

RE: Thumb rule for fillet size

(OP)
Dear sir,
YEs, is for 75% of minimum thickness.
I assuming it as a leg length of fillet.

Regards
Prasad Rode

RE: Thumb rule for fillet size

If you're dealing with plate that thick then I assume you are talking about significant loads. You shouldn't be messing around with rules of thumb but size the weld based on the actual loads.

RE: Thumb rule for fillet size

spot on Dozer!!!

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