Installing a Jacobs drill chucks on its tapered shank. Morse taper shanks are intened to be inserted into their sockets and seated with a light tap. The thrust of the drill will seat them.
Jacobs tapers like on a drill chuck are a different deal. The best installation is a shrink fit. Make sure the male taper and its socket in the chuck are clean and grease free. Warm the chuck in the oven to 350 degrees which takes about 1/2 hour. It will smell a little but that’s normal for warmed lubricants. Wait til SWMBO is out of the house with all the little tattletales.
Using an oven mitt, grab the chuck and slip it solidly on the shank taper and hold it in place for a moment. Set the assembled chuck and shankaside and allow it to cool. This is a more solid fitting of tapers than you could attain with anything short of a press. Do not stroll casually from the house to the shop to install that chuck on the taper. In those few minutes the chuck can lose significant heat and thereby affect the its retention on the shank taper. Assemble the chuck on the shank right at the oven. Do not dally.
Most all materials expand when heated and contract when cooled. Steel is no exception expanding 6.5 millionths of an inch per inch per degree Fahrenheit.
Everything in the machinist's trade works by the numbers. If the big end of the taper socket is 5/8" diameter and you warm it to 350 degrees you have a temperature raise of 350 - 70 = 220 degrees F. 0.625 x 6.5 x 10^-6 x 220 = 0.0009" expansion. Work some more numbers and you get roughly 43,000 PSI hoop stress in the taper. It would take about 3500 lb of force (figuring friction) in a press to secure the same chuck retention.
A press is a significant and seldom used piece of shop equipment. In this example clever use of the family oven to shrink fit a Jacobs chuck on its shank eliminates the momentary need for an expensive press. Alternatively, it also eliminates the shock and damage hazard of driving the shank into its socket with a lusty hammer blow.
