Yes, this will fit a Delta Shopmaster ss250.
Yes, this will fit the SS350 Scroll Saw.
Yes, it will cut 1.2mm brass plate.
The blades are 8.875 inches long.
The Delta #2 Super Sharps Scroll Saw Blade is a compatible fit for your Delta 40-680 P-20 20IN Scroll Saw'
According to the manufacturer’s (delta’s) website, the #2 has 20 TPI
Yes, this will fit your Delta scroll saw.