Spindle-temperature anxiety & square holes

[durableoreo]

I've been making square holes all week, for custom sockets. I drill and bore the bulk of the material on the lathe, then move to the mill. The corners are drilled at 1/8" and then the hole is squared off with a 1/4" endmill (SC, 4 FL, 1" LOC). The drill is small and the endmill is carbide so I'm running at about 2,000 RPM. Yesterday, I noticed that the spindle nose was getting very hot---much hotter than usual. I continued to work, taking breaks when the spindle was too hot. Eventually I replaced the endmill and everything went back to normal. Apparently the endmill was badly worn and doing more than its fair share of rubbing. The heat was moving through the tool holder, into the spindle nose. The sound of cuts immediately changed and the chips came out much longer.

It takes me about 15 min to do the mill work. Is that reasonable? Any productivity tips?

When I started, I used a drill chuck and a hole starting drill. Now I have a short 1/8" drill in a tool holder and just peck a bit to get a good start. That saves a lot of Z movement. The Z-axis is motorized but it's slow and I have to watch it every second. Without the chuck, all the tools are similar length so I can crank the X-axis over and do a tool change to the side of the vise.

 

[Eddyde]

Broaching, either conventional or rotary would certainly speed up the process.

 

[RaisedByWolves]

What material?

You most likely don’t need to be running that fast.

 

[extropic]

What size is the square?
How deep is the square?
Blind bottom or through the workpiece?
Describe the mill.

 

[durableoreo]

What size is the square?
How deep is the square?
Blind bottom or through the workpiece?
Describe the mill.

The material is annealed 4140.

The hole is the drive end of the socket, 3/4 across, 0.813 deep. I drill the blanks out to 0.625 on the lathe. The hole goes thru to the other side of the socket, which is quite a bit larger than the drive hole. It does pack full of chips, though, so I'm also using a vacuum to draw chips out of the pocket. And the air compressor kicks on occasionally, for maximum noise. The mill is the green type of RF-45 with DRO

 

[extropic]

I don't see any reason not to drill to 3/4" on the lathe. Drilling is usually the fastest way to remove material.
1/8" drilled corners + 1/4" end mill leaves some material to be removed near the corners. Are you finishing the square with a file?
I'm still not clear if the .813" is the length of a through square or the depth of a pocket. If it's a through feature, one of the small power files should speed up the finish work. Example only

If the design allows, and financially feasible, drilling through and using a square broach, instead of file/power file, should speed things up.