SKM-88 Dimensions

[Dehn0045]

I was curious about the dimensions of the SKM-88 mechanism, but after searching here and elsewhere I wasn't able to find what I wanted. Specifically I was looking for the largest diameter (the point just above the threads). Anyway, I just ordered one and took a bunch of measurements. Eventually I want to learn Fusion360 and will make a go at modeling this, but until that happens I figured I'd post up the measurements and photos I took.

One thing that wasn't totally obvious to me until I took it apart is how the little ball bearing works. It's important to realize that there is a small groove in the 'cup' piece that keeps the bearing at the same 'elevation' relative to the piece but allows the 'cup' and 'plunger' to rotate relative to one another.

Measurements are thousandths of an inch

 

[magpens]

Sam, thanks for posting these dimensions and the pictures of the SKM-88 internals.

I had a post a few months ago asking for exactly this information but nobody had it at that time !!!

Of course, I do have calipers and therefore knew the basic external dimensions but it is great to know the internal structure.

One other number for your future Fusion360 document is the external taper on the cup piece which I calculated to be 1.27 degrees.
Your measurement data yields a value of 1.36 degrees which is pretty close to my value.

Thanks again !!!

 

[nobodyparticular]

Fusion 360 is a good tool - I learned it last year and love it. I won't deny that it also made me scream a few times when it crashed, but overall, it is excellent. If you have ever worked with one of the other parametric modellers (such as Solidworks or Alibre), it is easy to learn. There is also a good amount of video tutorials on youtube.

 

[Jim15]

Thank you.

 

[Dehn0045]

One other number for your future Fusion360 document is the external taper on the cup piece which I calculated to be 1.27 degrees.
Your measurement data yields a value of 1.36 degrees which is pretty close to my value.

I found the smaller OD of the 'cup' to be a little difficult to accurately measure. There is a small chamfer and also the cup will flex a little due to the thin wall. I am sure my measuring technique could be better, but +/- a couple thou is good enough for me. Good to know that it is close to what you found!

 

[Dehn0045]

Also, forgot to thank those that led the way for me on this topic - @mredburn @More4dan and @magpens (among others) thanks for your posts and guidance