Milling in tight corners or deep cavities present machinists with a lot of different tooling requirements and machining parameters to consider.  According to this article from cnccookbook.com, the first step is simply addressing the common challenges of deep pocket milling; including tool deflection, which can lead to excessive machine chatter, wall taper, poor wall finish, and generally poor tool life and part quality. 

Deep Pocket machining will almost always require multiple stepdown passes to reach the bottom of the cavity.  The worse the tool deflection issues, the more passes will be required. It’s advised to focus on limiting the stickout, or projection, of the cutting tool from the holder as much as possible. We are speaking in the context of extended lengths, so this is relative to your part’s operation and desired wall depth. 

“In cases where you have flutes the full length of the tool, they’re going to be rubbing and potentially cutting the walls created by previous passes.  That needs to be minimized, and the right way to do that is to use tool shanks that have been relieved so they don’t contact the wall.”

While multiple stepdown passes are inevitable, machining parts with high walls require extended reach holders and end mills in order to mill at your required depths. Once your tooling is configured to reach your desired depth, we want to limit witness marks as much as possible, with each pass, in order to achieve the highest quality part. Techniks Extended length tools and SlimFIT holders provide the reach you need to get into the tightest spaces, combined with high quality, precision cutting tools, you can finally improve your deep pocket machining.