[TheForge] broken weld on mower deck

[jerry Frost]

I realized I should've mentioned size. For thin stock like a mower deck roughly the size of a playing card will do the job. There were calculations and rules in my welding books but last I read those was something like 45 years ago. Things change but rules of thumb  will usually do. If you're doing structural fabrication where getting it right is critical hire a pro.

Frosty

-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net] On Behalf Of jerry Frost
Sent: Wednesday, June 7, 2017 3:08 PM
To: 'Blacksmithing List Sponsored by ABANA'
Subject: Re: [TheForge] broken weld on mower deck

On a large area like a deck you want to fish plate the ends of the welds. Drilling stop holes is even more important. 

Another place to use fish plates is splicing structural steel like I beam. 

I believe trying to fish plate a large area like Terry's mower deck does more harm than good. 

Jer
-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Bruce .
Sent: Wednesday, June 7, 2017 3:36 AM
To: terry l. ridder; Blacksmithing List Sponsored by ABANA
Subject: Re: [TheForge] broken weld on mower deck

Jerry,
Was that ONE fish plate over the entire crack, or one over each drilled hole, or what?

Bruce
NJ

On Tue, Jun 6, 2017 at 8:48 PM, terry l. ridder <terrylr at blauedonau.com>
wrote:

> hello
> ​<snip>
>
> my paraphrase.
>
> drill a stop hole at the end of the weld.
> pull the broken weld together with gentle force.
> clean up the broken weld and remove any paint in the area.
> weld the broken weld.
> take a similar metal and weld diamond shaped pieces over the repair 
> weld.
> clean up welds.
> spray paint with kubota orange.
>
> repeat as necessary ;-)
>
> On Tue, 6 Jun 2017, jerry Frost wrote:
>
> No, don't try heat treating the welds. First thing to do is drill 
> stopper
>> holes at the ends of the cracks. After you weld it up, fish plate 
>> them it. A fish plate is a diamond shape piece of steel of the same 
>> or similar thickness as the piece being welded.
>>
>> NO! Do NOT use thicker steel it will defeat the purpose of fishplating.
>> You
>> want the fish plate to flex and spread the force over a distance. 
>> Slightly lighter weight steel is more effective. Fish plates are NOT 
>> reinforcements they distribute stress, two entirely different things, 
>> related but different.
>>
>> Fish plate the high stress or high flex zone. You lay the plate over 
>> the weld so none of the corners of the diamond line up with or fall 
>> on the weld.
>> Perimeter weld it over the weld. Mig it is good, the smoother the 
>> beads the lower the stress at the edges. Do NOT torch weld, the HAZ 
>> (Heat Affect
>> Zone)
>> is way too large.
>>
>> What a fish plate does is distribute the stress formed by the ends of 
>> a weld bead which is a stress riser. A final touch to maximize the 
>> effect is to run the beads towards each narrow end of the plate and 
>> carry the bead past the point in a J shaped finish. Called a "J 
>> tail."
>>
>> The "J tail" distributes any flexing stress over a distance in a 
>> curve leaving no stress riser.
>>
>> I hope this is clearer than it sounds.
>>
>> Frosty
>>
>>
> --
> terry l. ridder ><>
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