Hi Tyler,

1) OK, but read 5) below before concluding (although you might still be right!)

2) No, what I meant was just upgrading to profile rail would not help unless the underlying structure was improved. So I agree if going with the steel beam upgrade (which is your plan) then I would recommend doing both the steel beam and the profile rail.

3) I'm OK with you including the URL in the text box below the video on YouTube for the calculator and the forum site. Lee Roberts is the site owner and I'm sure he will chip in if there are any issues with that.

4) All I did was divide the force you applied (converted to N) by the displacement you measured. The only with any real meaning is the force and displacement applied at the collet/cutting tool so make sure you include that.

5) To get the bigger picture when the force is applied to the collet - what I understood you had done is apply force at one location (say location A) , and measure the displacement at that same location (location A). Then applied the force to ANOTHER location (say location B), and measure the displacement at location B, and then the force at location C and the displacement at location C.

I'm saying don't do it like that. It is much more helpful to apply the force to location A, then measure at A (A being the collet/tool). Then apply at A again, and measure at B. Then apply at A again and measure at C, etc. Do not move the force location, only the measurement location for the deflection. Then by looking at the numbers, or plotting them on a graph, you can see where the stiffness falls away and where the improvement is required in the structure. You can also apply at A, and measure the displacement at A,B,C,D etc if you have enough DTIs. If this is what you did then carry on.

The short answer to all the above is:
Used closed sections - e.g. rectangular hollow sections [], not [, U, or I

Maximise their outer dimensions (this gives stiffness improvements to the ^3 for a linear size increase)

Then up the wall thickness until the weight is getting too high (this gives stiffness improvements directly proportional to increase so is not as effective as outer dimensions)

Minimise offsets, these create moments which you will not fully recover through beefing up elsewhere

Be practical - consider the principles, but you have to be able to build the machine !