Issue description:
I created a hammer with a cobalt head in Direwolf20, which has the Momentum trait. Regardless of any (other) speed increase it has (from stonebound, redstone, momentum), it seems that the mining speed is capped at a fairly low speed. I'm wondering specifically about momentum as it is supposed to add 40% (really significant) speed while mining. The source code says it's a potion, but I cannot see any potion effects while or directly after mining. Is this an issue with the hammer mining speed being capped at a certain speed regardless of the speed shown in the tooltip?

Versions:

• Minecraft: 1.12.2
• Forge: forge-14.23.5.2821
• Mantle: 1.3.3.42
• Tinkers Construct: 2.12.0.115
• Modpack: Direwolf20 1.12, version 2.5.0

Can it be reproduced with just Tinkers Construct? If not, list the other mods required to reproduce the issue.
Reproduced in Direwolf 20 in a superflat "redstone ready" world. Tested by mining the sandstone found in the world. Issue appears to be just Tinkers Construct, so I suppose no other mods are required to reproduce the issue.

There is no visual indicator. It stops shortly after you stop breaking blocks. So, as long as you keep breaking blocks, it will increase mining speed, up to a max, and then reset. Especially with hammers it's usually noticable in the first few blockbreaks.

I've heard various "testimonies" from people saying this works to think its working fine, if its not working fine I really don't have time to return to 1.12 to debug it. Call the current behavior the expected behavior and use a different material if its not strong enough I suppose.