Newbie question about morse tapers

[epanzella]

The tang goes into a slot in the tail stock that stops it from spinning under heavy loads.

 

[Parlo]

The tang goes into a slot in the tail stock that stops it from spinning under heavy loads.

Lots of different opinions on whether the tang is to supplement driving the tool. Generally it is for ejection only because if it does ever get to the stage where the morse taper slips, the soft tang is easily twisted. The size and angle of the Morse taper is calculated to deliver the required torque for the size of the tool but only works well if the tapers are clean and in good condition. Most slipping occurs when the tool is not driven into the taper socket. Some text say that tool pressure is enough to seat the taper, this is not always the case.

 

[epanzella]

To get more tailstock travel before ejection I cut the tang off one of my MT# 3 drill chucks and it would slip once in a while with large drill bits (1.00 plus). I ended up welding the tang back on again. No more slippage. If the tang was not to prevent slippage, why is the tang a rectangular shape and why is there a matching slot to receive it inside of the tailstock. My live centers don't have tangs and they still eject just fine.

 

[Parlo]

To get more tailstock travel before ejection I cut the tang off one of my MT# 3 drill chucks and it would slip once in a while with large drill bits (1.00 plus). I ended up welding the tang back on again. No more slippage. If the tang was not to prevent slippage, why is the tang a rectangular shape and why is there a matching slot to receive it inside of the tailstock. My live centers don't have tangs and they still eject just fine.

If a morse taper slips it is usually due to it not being seated properly for all the usual reasons, the most common is not hit home hard enough. This is a variable that can't be controlled by the drill designers, although there is a safety factor built into the morse taper size for the particular size drill. As you have had slippage in the past it may be a idea to check your tailstock and drill chuck for galling to help with the taper engagement.

The simplest way to have ejection for tapers was decided to use a tang and drift. The predominant reason is that it is fairly easy to put a through slot in a spindle for a drift. By machining a slot through the spindle it automatically leaves a rectangular aperture that is ideal for a tang. Although the tang looks ideal for driving it's often mistaken that it's the primary role, it's just to fit into the aperture in the spindle.

Live centres do not usually eject using the slot for the drift, they tend to be too short for the drift to eject them. The tailstock ejection pin will eject them though. They don't have a tang because they are not driven.