Subtracting a countersunk screw profile

[Kevin Keys]

I am wanting to subtract the shape of number 8 machine screw from a solid object and not having much luck. I keep getting error messages saying it I need to 'edit the geometry'. As a workaround I can accomplish the task by using the '3d threaded shaft' tool, then using a portion of the '3d hole tool' but its much more time consuming to do it this way. Perhaps I am missing something.

[Guest]

Kevin,

You're not missing anything. The threads of the machine screw object consist of several sweeps which don?t always work well when trying to subtract from another solid (as you obviously have found out.) The 3D threaded shaft and 3D hole are true solids which is why they can be subtracted. What is needed is a 3D Threaded Hole Tool, which is on my wish list. Until then, what you are doing is the only workaround.

Tom Urie

Nemetschek, N.A.

[Kevin Keys]

Tom

Thanks for clarifying that. At least I know I tried everything I could. That would certainly be a great wish list item for the future.

Also..........in the arsenal of screws I dont see a "Deck screw" with appropriate threading and head styles ( eg bugle head) Is there one hiding there somewhere??

Thanks

-Kev

[islandmon]

http://www.fractalnet.org/gallery2/v/CAD/CAD_ThreadSolid.jpg.html

[AndiACD]

Tom's hit the nail on the head here, but you'll find that there IS a way around it(forgive the pun. Ouch!) i've been moaning about the unwanted "you have tried to create an object that can't be computed, edit the geo . . . . . ." that's when i hit the head, mine against the desk.

Now, if, when you have the screw, bolt, grub placed where you want it and VW refuses to accomodate, select just the screw in the front view(assuming it is vertical, but left, right, back, plan all work, depending obviously on the orientation of the screw. Look at it side on) and zoom in so the thread fills the screen and use the "Nudge" function(Shift+Up Arrow/Down, Left or Right all work) this moves the object a small amount but often it's enough. Try and subtract again and it should work.

Why it works is because when adding or subtracting objects VW detests any lines that overlap or cross each other so if you find VW complaining that you can't do this, look closer at intersecting lines like the head of the screws profile and if it's flush with the surface of the material you need to subtract it from, adjust the position(100ths of a mm are usually enough) till it's happy and does what you want. Movement is small so it shouldn't affect the accuracy.