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Update to broaching a 7/8" square hole


Cast Iron
Jan 4, 2013
From time to time when someone asks me to do a job, information is lacking to varying degrees. Generally important details are left out or in some cases just not known about when discussing the job. Such is the case with this project https://www.practicalmachinist.com/...3-diameter-blind-flange-inexpensively-370109/

After the fluff went away the blind flanges were actually drive hub blanks made from 4130 or 4140 2 3/4" diameter by 1 3/4" thick. The position of the corners of the 7/8" square are critical radially and the actual square dimensions need to be 0.005" larger for clearance purposes than a standard broach produces.

So it looks like I'll be using a slotting head on a mill with a rotary table to produce the square holes.