Friday, May 20, 2016

Part #4 - The First Milling Test

I figured it would be safe now to try some milling. The posts I read claimed there is too much flex in a drill press to mill well. After tying it the finish is not great and could definitely use some improvement. The head needs to be trammed and the lack of a real spindle lock also caused some uneven surface milling.

Rough Surface Finish.
There was some chatter causing some scalloping of the finish. Not horrible for a first test but room for improvement. I learned the hard way how much to tighten the collet nut and work clamps. While trying out my brand new rotary table the bit grabbed the work, pulled it into it which caused the bit to drive into the table face. Now I have a reminder to tighten things well.
You can see where the bit grabbed and milled down to the table surface.
  And the reminder.

Flex Testing
So after some goofing around milling this and that I figured I should measure the amount of flex I was getting between the bit and the work piece. Using a dial indicator, a scale, and block and tackle I pulled down on the table and measured from the table surface to the spindle and with 50 lbs I had 8.5 mil of flex. I also noticed that if I rapped on top of one of the corner of the table closest to me it rang like a bell. Those are big problems.
 The Table Flex Test.
I also set the table height with 16" of column between the table and the head and pulled down on the head with 50lbs and saw 7.5 mil of movement. That would be the column flexing.
The Column Flex Test.

At some point I still need to measure the column twist. I need to think about how to best do that so I haven't do it yet but I will.

Now that I know how much flex I have I have to figure out a way to reduce it. 

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