Hi Martin.

providing we're talking about the taper fitting for the chuck to the mandril, make sure the taper and the hole is perfectly clean (no oil) and dry……..put them together with push and twist…thats it job done….some say a light tap to get them to seat together !!!!!!!!!!

clogs

Plus 2 for Clogs, drill chucks don't have a drawbar. If you do give it "a light tap" to seat it (I always do) use a soft mallet and make sure the jaws are withdrawn into the body before you hit it.

I have just swapped a B16 mount drill chuck over from a MT3 to an MT2, it has been on the MT3 for a year. The chuck was opened to its full extent so that I could put a rod up to the base of the B16 taper, gave a sharp tap and the taper released ( as expected). Then a quick wipe on the B16 with MT2, place it in the chuck, a quick tap on the bench with the MT2 small end, job done.

Always done it this way and never had anything come off. intact it is usually the other way round, trying to get the !!!! off.

Martin

It is a drilling chuck, the pressure on it is axial. The pressure on the drill pushes it into the taper.

Does using a slot milling cutter count? I have to admit to using them for small counterbores, on occasions. Would agree that using the cutter's side faces is not to be recommended, with a drill chuck.

Pete

According to Wobblypedia "

R8

This taper was designed by Bridgeport Machines, Inc. for use in its milling machines. R8 tapers are not self-holding, so they require a drawbar extending up through the spindle to the top of the machine to prevent loosening when lateral forces are encountered. They are also keyed (see image) to prevent rotation. The drawbar thread is typically  ⁷⁄₁₆″–20 tpi (UNF). The angle of the cone is 16°51′ (16.85&deg with an OD of 1.25″ and a length of  ¹⁵⁄₁₆″.^[13] (source, Bridgeport Manufacturer) The resultant inner diameter is slightly over  ³¹⁄₃₂″.

Tools with an R8 taper are inserted directly into the machine's spindle. R8 collets are typically used to hold tooling with round shanks, although any shape can be held if the collet has the correct corresponding shape cut in it. The collets have a precision bore with axial compression slots for holding cutting tools and are threaded for the drawbar. The R8 system is commonly used with collets ranging in size from  ¹⁄₈″ to  ³⁄₄″ in diameter or tool holders with the same or slightly larger diameters. The collets or tool holders are placed directly into the spindle and the drawbar is tightened into the top of the collet or tool holder from above the spindle. Other tools such as drill chucks, fly cutters, indexable insert cutters, etc. may have an R-8 taper shank built into or added to the tool.

The R8 taper is commonly encountered on Bridgeport and similar turret mills from the USA, or on (very common) copies of these mills from elsewhere. The popularity is due in large part to the success of Bridgeport and other mills that were closely modeled after it and produced throughout much of the 20th century."