RPM to Torque correlation? Milwaukee tool specific


#1

I buy the tools for a maintenance department, we upgraded to Milwaukee a couple years back and the collection has been steadily growing.
Just bought a 2863-20 1/2" High torque impact (1000ft/lb max) for the occasional bigger stuff we have and I was wanting to define the 4 custom modes for the guys (this is the one-key version).
In the app they’re listed as 600rpm, 1200rpm, 1750rpm (which is basically 1/3, 2/3, and max), and then the “Nut busting” mode.
I assume i can’t just say those equal 350ft/lb, 700ft/lb, 1000ft lb (numbers rounded) but i’m not sure how else to figure it out as you can’t set specific torques, just RPMs in the one-key app.

Done some googling, but not coming up with much. Maybe i should just ask Milwaukee but I’m guessing if it were that simple they’d just state the facts.
Thanks for any advice!


#2

They might not know either as I wonder if they tested it. They would be the only people that might know the specifics however.

For a SWAG however I would say this. Typically with a brushless motor when you want it to spin slower it does provide less torque but it’s not a linear curve. SO it might be 1/3 the RPM but not 1/3 the torque - closer to 1/4. But there are many variables - the controller can decide it’s getting bogged down and ramp up delivered voltage but keep the timing slow - which increased delivered torque. There are some hobiest brushless motors that produce a set of torque curves based on controller settings - if you wanted to look for an example. something like this. https://www.linengineering.com/products/bldc-motors/bldc16-nema-17/

Anywho - I would guess that 1/3 RPM is about 1/4 applied torque to anvil, 2/3 RPM is probably closer to 2/3 applied torque to anvil. IIRC the 'nut busting" mode is a burst mode only in reverse and is the rated max of the tool. So max for application is less than that - but it’s been a while since I look it up.

Does one Key give you options to tailor the impact time or max duration. IE prevent someone from running a bolt down - holding the trigger too long and beating the snot out of it till it strips? Little surprise milwaukee didn’t make a correlation chart from one key settings and delivered torque - It’s how I would want it to work.