First of all I won’t call myself a gunsmith. This is my first time modifying a gun, you could say it is a much needed upgrade. Acquired awhile back a 1911 style ATI Titan .45ACP. The Titan is a 3.125" barrel akin to the Kimber Ultra Carry or Colt Defender. It has a notorious problem of being unreliable due to its having a two piece guide rod spring assembly. The fix is to replace the original with a Kimber one piece assembly.
The original collar or slide bushing is shaped to fit the ATI slide, but the Kimber bushing must be modified to fit. I found a Wen rotary tool kitwith flex shaft at Hobby Lobby for$22.99 last year model clearance, but a solid well built tool. I bought a set of fine work files at Harbor Freight for $4.99.
Pics show before/after, can only post 5 pics at a time so bear with me.
Tools
Parts - original has screw that can come loose and the main reason for fail to cycle properly. Kimber base plate permanently attached. 
