I don't see a way to "combine" these three blocks to a new block as you expect.
Furthermore, in dynamic blocks it is not a good practice to draw a lot of different variants and choose the needed variant from a list of "hundreds" of visibility states, if they differ only in their dimensions. The advantage of Dynamic blocks is, to draw ONE exemplar of the geometry, and then add dynamic parameters and actions to drive the dimensions of this model. To do that you can use either dynamic parameters and actions

or you use the "Parametric" (geometric and dimensional constraints).

In the attached dwg I show you an example how you can solve your issue using the second method. (I think some others will jump in here to show you how such blocks can be designed using the first method). Try to explore how it works, if you have questions - ask.
In the block table I included only the first three and the last three length's of the screws. You can add the missing rows for all the remaining sizes yourselfe.
Feel free to ask if you have further questions.
[EDIT]:
An additional note: Some of your block (I didn't check all) seem (for me) to be drawn wrong. M12-65 to M12-120 are 0.15 to long, M12-150 to M12-180 are 5 mm to short. Or I'm missing something?
Jürgen Palme
Did you find this post helpful? Feel free to Like this post.
Did your question get successfully answered? Then click on the ACCEPT SOLUTION button.
