I have 110vdc motor off exercise treadmill ; want to make grinder; how to convert acv110 to dcv 110 to use motor. Will diodes from car alternator be strong enough?

Are you absolutely positive that the motor is a DC motor right now, how were you getting power to it as a tread mill?

The 110vdc motor came put of a treadmill tore apart for scrap,(junked) at st. vince depaul store where I volunteer. People donate things that don't work, and is dismantled for recycling.I have the 110vdc motor which has the nameplate on it. How can I use 110vdc motors on 110vac house power?

You might try googling stuff on inverters but I think they would cost more than just buying a new ac motor.

They are usually used with motor controllers which may use pulse-width-midulation to vary the speed and keep the torque nearly constant.

Assuming a 2 HP motor
I = 746 *2 / 120

I'd use a 30 Amp rectifiers with a 600 V Peak inverse voltage rating.

See Full wave bridge - resistive load here: http://www.hammondmfg.com/pdf/5c007.pdf

Bridge rectifiers have to be heat sinked and have markings for ~,~,+ and -. You also need to use grease.

You can try to find this stuff on the surplus market or

US - Electronic Components Distributor | Newark.com (http://www.newark.com) and/or Digi-Key Corporation - USA Home Page (http://www.digikey.com) or www.mouser.com (http:///www.mouser.com)