Knockout bar upgrade

[peltona]

Messed up OEM brass end when trying to knock out an MT2 ER40 collet holder. Ended up turning a larger one from brass and figured I'd share the rough sketch I made up to do so. This in fits the spindle through bore so much better.

 

[petebucy4638]

Messed up OEM brass end when trying to knock out an MT2 ER40 collet holder. Ended up turning a larger one from brass and figured I'd share the rough sketch I made up to do so. This in fits the spindle through bore so much better.

View attachment 226900

The knockout bars on both of my lathes are steel. I upgraded them to HSS, just to have the excuse to make some wood handles for the new bars. I could see where a brass end could be an advantage.

 

[bob vaughan]

Stainless steel is a good choice since it is softer and weaker than regular steel.

 

[peltona]

The knockout bars on both of my lathes are steel. I upgraded them to HSS, just to have the excuse to make some wood handles for the new bars. I could see where a brass end could be an advantage.

I love making wood handles for my stuff too! HSS would stay nice and straight but it will for sure be harder than anything you stick into the spindle. The idea is to not deform your MT2 shank over time when you knock it out. Your spindle taper would also be softer than your knockout bar but since you are approaching form the narrow part of the taper, you should never risk scratching or marring it.

 

[peltona]

Stainless steel is a good choice since it is softer and weaker than regular steel.

That hasn't been true in my experience with machining and metallurgy. I guess it depends on what you mean by "regular steel" 1018 is most Common steel with a Rockwell hardness of B71. 304 stainless steel is much harder, with a Rockwell hardness of B88 and 316 is B95. From what I could find looking quickly, most spindles are made of 4140 which is off the B chart of Rockwell in terms of hardness and switches to C25.