Home made press for straightening crankshafts
Model T cranks were straightened by bending them both during the manufacturing process and while in service during Lizzie's  heyday.....
This gang of deaf guys is finish straightening the crankshafts before they go to the machine shop.
The Ford Service Manual had this to say in paragraph 242 , ".....If the shaft is sprung less than .012"  it can be straightened on a press (See Fig. 163).  If shaft is sprung more than .012" a new shaft should be installed."   Figure 163 shows a crank being straightened in a hand-operated press.
Press is made from a junk Model A block and built on 12" channel steel.   Block was milled out to accept a 5/8" dia. steel rod with a brass tip - is operated from below by a small hydraulic bottle jack.
Our grinder is an older Storm Vulcan No. 15
Inverted bearing cap serves as guide for the operating rod.
In use, the crank is first "dialed in" on the crankgrinder to determine how much it is sprung.  Straightening is accomplished in the press using the dial indicator to show amount of correction.  We have found it necessary to straighten most Model T cranks prior to grinding them.

Crank shown is a Model A which has been modified for use in Model T engines - these always warp when the counterweights are welded on necessitating accurate straightening prior to grinding. 
Phil Mino
Strathmore, CA