Total speed including skills etc would be 120 for max hits per second, anything more does nothing extra, but less reduces the hits per second.
It was discussed in this thread:
Essentially it means if you can get the tool speed to 80+ (not including skills) then have max skills (+40) that should top it out, without having to use speed brews.
You can see the hits per second never goes above 8.2, but the drop off at 119 or under is to max 5.3, which is quite sharp when you are used to the upper limit!