How Do You Mill A Piece Taller Than Your Z-Travels?

Manual machinists with knee mills will recognize this trick of hanging the workpiece off the table’s edge, but it’s the first time I’d seen it done on a CNC:

A very near thing!

I asked the machinist about the rigidity of this setup and he pointed out the workpiece is PVC plastic–cuts real easily if you don’t get carried away and melt it. He said if it had been metal, he would’ve machined a special subplate to go under the chuck with a pass through for the workpiece, and he would likely also have stacked some 4-6-8 blocks to raise the chuck up so much less of the workpiece protruded above the jaws.

The alternatives are either a right angle head or a live tooled lathe with some really big capacity for a job like this one. BTW, you also have to make sure your table travels will let the head get enough access off the edge of the table.

Last thing–see the note about the indexer centerline? Do you take out a Sharpie and write notes on your tooling like that? You should! Put the information where it is handy and won’t get lost. I make all sorts of notes and marks all over my shop, the machinery, the workpieces, and the tooling. For example, I marked the travels on my lathe’s compound so I can see when I’m getting close or how much travel may be left at a glance.

I never get tired of seeing new fixturing and workholding ideas. If you have some, drop me a note and a photo so we can share with the CNCCookbook crowd!

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