Jeff Petrie (35) then stood firm as Armadale looked on top at 2-84, and even 4-126.
Batsmen reached double figures but Anton Bickley was the last man out as Armadale posted 170.
In reply Damian Carroll snared an early pole as Cockburn reached 1-47 at stumps.
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READ NOWThird Grade won the toss in their clash with Jandakot Park and started well thanks to Rylan Arms, who made a fine 58, while Rob Zagari made 21 and Alex Cumming 30.
But 2-117 became danger at 6-143 before Paul Edwards (42) and Jorden Dobson (41 n.o.) rallied beautifully as Armadale made 234.
One Day As have defeated Champion Lakes, who won the toss and batted.
They started well to be 1-66 before Asim Meh-mood (2-25) and Raebern D’Sylva (3-16 off 8) bowled beautifully in the middle stages as Champion Lakes crumbled to 7-105. But they fought back and posted a competitive 8-165.
Oswin D’Sylva (32) and Christian Furk (27) batted well, but a few quick wickets had Armadale nervous at 5-123. Paul James made a handy 45 as Armadale cruised with 7-212.
One Day Cs have had a good win against Kardin-ya after batting first.
Armadale got off to a good start, as George Knowles made 35 and Calvin D’Sylva 25.
At 1-68 things stagnated, as no one else got over 11 and Armadale was rolled for 169.
In reply Armadale came out bowling fireballs as Haydon Wilson (4-13), George Knowles (3-17) and Mitchell Marsh (3-35) ran through them as Kardinya slumped to 9-66.
In the end Kardinya was all out for 101.
One Day Es have demolished Hilton.
Steve Jones made 34 before Lee Cover and Dave Armstrong went to town.
Cover was particularly savage as he made 158 n.o. while Armstrong made an even 100 n.o. with one six and 13 fours.
The pair put on a magnificent unbroken 225 as Armadale amassed a mammoth 3-346.
In reply Hilton was rolled for a miserable 67.
One Day Fs have had a good win against Piara Waters, who batted first and started well to be 1-60.
Armadale First Grade has made the one-day grand final against Cockburn at Davilak Reserve, starting at 1pm.