Jeff Bratt
04-18-2010, 3:40 AM
I've had a page here (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower.html) for awhile documenting the inflated HP ratings common on small power tools. Now I've added a new page (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower2.html) with more detailed explanations of how motors are rated, simple HP calculations, some performance graphs, plus links to even more motor information.
This can still be summed up by a few simple rules:
1) At 120V a motor will need about 10 amps per horsepower. Anything that plugs into a US standard 120V 15A outlet is - max - 1 1/2 HP.
2) A motor that is NEMA compliant will have comprehensive nameplate which includes a rating for continuous HP - among many other ratings.
3) If a tool has only a "peak", "max", or "developed" HP rating, that number is not at all comparable to a real, continuous HP rating - it is there to try to make you think that tool is more powerful than it really is.
The new page includes an explanation of why (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower2.html#A_Real_Life_Comparison) a 3.5 HP router motor is nowhere near comparable to a 3 HP shaper motor - the shaper motor puts out at least twice the power of the router. This is in direct reference to a previous thread (http://sawmillcreek.org/showthread.php?t=134401).
This can still be summed up by a few simple rules:
1) At 120V a motor will need about 10 amps per horsepower. Anything that plugs into a US standard 120V 15A outlet is - max - 1 1/2 HP.
2) A motor that is NEMA compliant will have comprehensive nameplate which includes a rating for continuous HP - among many other ratings.
3) If a tool has only a "peak", "max", or "developed" HP rating, that number is not at all comparable to a real, continuous HP rating - it is there to try to make you think that tool is more powerful than it really is.
The new page includes an explanation of why (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower2.html#A_Real_Life_Comparison) a 3.5 HP router motor is nowhere near comparable to a 3 HP shaper motor - the shaper motor puts out at least twice the power of the router. This is in direct reference to a previous thread (http://sawmillcreek.org/showthread.php?t=134401).