Issue with rotating part and then union

charles_pharis

I am attempting to make a screw shorter, I only have an STL of the screw and I figured it would be faster to just split the part into 3 pieces, remove the extra piece and then union the 2 parts back together. Everything works fine except for when I rotate the screw to make the 2 parts align properly. If I don't rotate the union works fine but the threads are misaligned, if I rotate 1 of the parts to align the threads then the union won't work. I don't know what I am doing wrong, please help.

https://cad.onshape.com/documents/dca58e8038c904b6b7988b57/w/43625d3469482a06013761d8/e/dc93d189eb66e7f811fa66f2?renderMode=0&uiState=6448e368e9ee737e0c27f1c3

robert_scott_jr_

Hello Charles. Since you've received no replies to your inquiry I will offer my unprofessional guesses and possible suggestions to you.

I took a look at this screw in section view. Inside the part are multiple lines that are nearly invisible. I poked around the internet and found this describing an STL file: 'Each file is made up of a series of linked triangles'. Based on that, I don't think CAD will be able to handle it as a solid. I suppose that when a section is removed the chances of the multiple faces on the remaining parts matching up are slim.

However, during my poking around I did find some hints that there are programs out there that can take the STL and convert it to something CAD can deal with.

McMaster-Carr can be a friend in need or even Oshape's own Standard content to provide you with CAD files. If you know the specifics of the the screw you posted you may be able to manipulate it to your goal.

-Scotty

wayne_sauder

@charles_pharis
I would try to find a STEP. file of the screw, if that is not possible then I would probably try a workflow like this. https://cad.onshape.com/documents/e6a286ed4b1ad98f8e943b69/w/cc5056d31c96081ccefd8f1c/e/5e311fd56464440c3128470b

john_lopez363

@charles_pharis
It appears to me that you are simply try to preserve the face profile of the screw after you've "cut it" to size.  If so, here is simpler approach, in my opinion anyway.

1). Split the part at your desired distance
2). Create an enclosed sketch that has the profile of the face you'd like end up with, perpendicular to the central axis of the part.
3). Revolve (remove) that enclosed sketch

Link to see how I did it.  
https://cad.onshape.com/documents/cada2a2f8dc010d69f9b963e/w/014992107cdb46c8283cde8f/e/8ebb0ea09ff5abede29ca980