Originally posted by newarts Depending on how much vodka the Helios assembly line workers had consumed (ie how carefully the lens was assembled) the flanged adapter might or might not cause loss of infinity focus. If using the Helios for portraits, closeups, other shots where infinity doesn't matter, that's no big deal. And I've read that infinity is easily adjusted on the Helios.
Yes, the flanged adapter *does* provide a much tighter, more secure mount. The unpainted (metallic) ones will (safely) short the mount contacts for CIF use. But if only painted (black) ones are available, scraping off the paint at the appropriate location is no big deal either. I probably have a dozen scraped-paint adapters (M39, M42, macro) in my kit. I use the file blade on my Leatherman tool for that.
One thing NOT to do: It's common with PK-M and M42 mount lenses, to stick a bit of metal tape on the lens base, to short those contacts. DO NOT PUT METAL TAPE ON A WIDE-FLANGE ADAPTER like a flanged M42-PK adapter. The tape's thickness WILL cause the adapter to jam on the camera mount.