[TheForge] fish plates? just how big are they?

[jerry Frost]

I was hoping someone else who knew how to do this would speak up. Glad for
the input Jenifer. In the OP Terry expressed his in inexperience and doubt a
repair would work. I felt a little moderate overkill wouldn't hurt and give
him a little confidence. Like Dumbo's feather.

My only difference with your experience is to mention how badly the deck is
bent up effects how serious you have to get in the repair. But, yes an
experienced welder wouldn't need more than a stop hole in the break's ends.
Fish plating is for heavier repair or less skilled welders.

I don't have a Tig welder so it's GMAW or stick, making my beads heavier but
I have a needle scaler that does a wonderful job of stress relieving welds.
Then I grind them smooth and flush. 

Terry: No, that's way too small. The fish plate is there to distribute
stress and making a fish plate the size of or smaller than the weld bead
will only make it worse. You have to add up all the beads around the tiny
little fishplate you're thinking about. 

Do NOT put a fish plate on a mower deck smaller than a business card and
that's pushing it. 

Frosty

-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net] On Behalf Of J. Petrila
Sent: Wednesday, June 21, 2017 9:07 AM
To: terry l. ridder; Blacksmithing List Sponsored by ABANA
Subject: Re: [TheForge] fish plates? just how big are they?

while from a structural stand point fish plates are supposed to help shed
the load from the area that was damaged/joined and disperse it over a larger
area.. thus reinforcing the area and joint..

I personally only drill out the cracks once I have straightened out the
sheet metal as the cracks will propagate as the metal is pushed or hammered
back to where it belongs..

Ideally the thickness of the plate should be the same or slightly under the
parent material but it's a mower deck..   If welded properly even with no
fish plates it will hold up just fine..

I've done maybe 20 of them (fixed for money) and I've only had 2 come back
but not for anything where I fixed it.  The guys were prone on running into
stuff.. I think they were crashing the mowers on purpose..

I used to clean everything spotless and then tig weld it back together as
TIG welding offers the best Ductility and elongation but I found it was way
overkill..  I thin just started to clean everything, drill the ends of the
cracks, weld the cracks full penetration, then grind off the part of the
welds that were overly high.. and call it a day..

On large tractor decks, bush hogs and such they get fish plated.. Or if it's
a structural beam like on a gantry crane..



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