M Rokkor f2/40mm Help

[f16sunshine]

Recently I bought a pair of CLE 40mm f2 lenses.
It was an accident to get 2 but a happy one.
Yesterday I decided to file down the mount on one of the lenses to bring up the 35mm frame lines on the M8.
The helicoid on the body side is connected to the mount flange.
I marked the matching up location as I removed it.
The problem I'm having is meshing up the threads.
The two sides just don't want to catch and screw together.
As I have tried again and again now my sharpie mark has been rubbed off as well. The threads are both clean and perfect...I see no reason for the problem.
Any tips on how to get things settled down and into place and how to locate the correct orientation for accurate focus?
My last resort is to send the lens in. Seems silly for such a mundane task.
Thank you for your comments.

 

[Al Kaplan]

It just takes a few quick strokes of the file. There's no need to take the flange off of the lens or unscrew the helical. You don't even have to be neat when you file the lug shorter. The Spirits living inside the don't give a hoot what the lug looks like.

 

[ferider]

Andy, this happens. Have a beer and try again patiently. The two helixes must be perfectly parallel. Don't force it.

 

[f16sunshine]

Thanks for the advice guys.