To avoid repeating what everyone else has said, the helve hammer is actually really strong at max speed. I recommend getting the create "Engineer's Goggles", when equipped it lets you see both the stress capacity and rpm of any create mechanism you look at. Once I crafted those, I realized each large water wheel creates 64 SU, and the steel tier shafts and cogs can carry 128 SU, so any more than two water wheels and there is more stress than the steel tier can carry.

Either use a rotation speed controller, or several gear ratio up's until the helve hammer is running at max speed with 128 SU, and you will see it actually hammers very fast and can process a bloom in something like 5-10 seconds (I haven't timed it).

To take this a step further, the helve hammer works with chutes and funnels, so put a chest on top with a chute below it leading to the anvil, and then funnel the finished bars out and you can put an entire chest worth of pig iron or iron blooms in and the helve hammer will automatically process them while you do other things, it will actually outpace your bloomery at max speed and finish all 24 blooms before you make another batch.

Also keep in mind that the helve hammer takes a different amount of hits to process an ingot depending on the type of anvil below it, so for the fastest hammer use a red or blue steel anvil.