Taper

[timothy42b]

I came across an interesting article about the history and current use of the Morse taper.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779551/

[boneagain]

I understand why the 5% tangent was so attractive (it's relatively easy to set a lathe up VERY accurately using length and offset measurements, whereas it's darn tough to set one up with ANY accuracy using a protractor.) But I wonder if he did much experimenting before selecting THAT value. I remain thoroughly impressed at how securely Morse tapers hold tooling in lathes, milling machines, and drill presses. The basic principal of operation is simple genius: friction is a function of coefficient of friction of mating surfaces and force applied. So, for any given material, the Morse taper uses the inclined plane principal to multiply force applied in proportion to the end load on the tool. In other words, push harder and it sticks more. Try that with a three jaw drill chuck! Hmm... my three jaw drill chuck uses one taper to hold the chuck on the mandrel, and a Morse to hold the mandrel in the drill press spindle.

Another question comes to mind: I wonder why they call it a Morse taper when there is basically NO interchangeability on the hip components? The whole idea of the Morse taper was to get something out there that would encourage interoperability between machines and the tools Morse made. Isn't this kinda the opposite direction?

[Kbiggs]

The taper is there to fit the ceramic head to the titanium shaft. The ceramic heads are of different sizes and shapes to fit different joints. The virtue of the Morse taper as part of the joint is, as you note:

The basic principal of operation is simple genius: friction is a function of coefficient of friction of mating surfaces and force applied. So, for any given material, the Morse taper uses the inclined plane principal to multiply force applied in proportion to the end load on the tool. In other words, push harder and it sticks more.[...]