[kstrauss]

Saunder's recent YouTube on plunge milling (https://www.youtube.com/watch?v=tlckRNfeXYI) prompted me to try some experiments. My Tormach supplied 3/4-inch shear hog is not quite centre cutting and leaves a central spike perhaps 25-thou in diameter. Is this usual?

[Steve Seebold]

I have been using plunge ruffing routines for several years.

I manuface a line of running gear and tools for my remote control race boats.

Some of those parts have a significant amount of material removed and plunge ruffing is the fastest way to remove material.

[mountaindew]

Steve mentioned this a while back and I started drilling out pockets as a normal part of my part setups. I found it to be faster and far less impact on cutters in deep pockets. BUT, The flip side is my spindle bearings now get hotter then ever. This makes me wonder if I this type of milling is best for large areas. I was thinking of going back to plunge hole for cutter entry and mill out with horizontal paths.

[Steve Seebold]

Steve mentioned this a while back and I started drilling out pockets as a normal part of my part setups. I found it to be faster and far less impact on cutters in deep pockets. BUT, The flip side is my spindle bearings now get hotter then ever. This makes me wonder if I this type of milling is best for large areas. I was thinking of going back to plunge hole for cutter entry and mill out with horizontal paths.

When I plunge ruff a pocket, the first thing I do is to drill a hole that’s the same size as the end mill so I don’t have my end mill flutes load up, and I “ALWAYS” use flood coolant.

[mountaindew]

When I plunge ruff a pocket, the first thing I do is to drill a hole that’s the same size as the end mill so I don’t have my end mill flutes load up, and I “ALWAYS” use flood coolant.

My cam software automatically finds any hole larger then the cutter and uses it for entry! So all I do is drill a hole in the pocket area then use normal cutter. I was drilling out large areas of the pocket and then using normal cutters to finish up. As I mentioned above this was much faster BUT, over time using this method put a fair amount of wear on my spindle bearings.

[Steve Seebold]

Mountaindew, if you’re experiencing spindle heating, you’re probably taking too much stepover.

As I said earlier I will drill a starter hole then plunge ruff from that hole.

For example, I will drill a 1/2 inch hole, leaving .015 to .025 stock from the drill point to the finished part, then I will use a 1/2 inch end mill running at 4,000 RPM and 30 IPM and a stepover of 40% of the diameter of the end mill using flood coolant and I have never had over heating problems.

I worked in a place many years ago where they constantly had spindle burnout problems and a bearing salesman finally convinced the maintenance foreman that he was putting too much grease in the bearings. On the next spindle rebuild, they cut the amount of grease by 2/3 and they never had another spindle problem.