Centering (aligning) a Woodruff Key in a Vertical Mill

[RickKr]

I need to cut a woodruff key slot in a cross slide feed screw (1/16" thick x 1/2 dia., key #204) . I plan to do this with a vertical mill, holding the feedscrew horizontal. I've have done some slitting of thin walled tubing (ferrule tabs on bamboo fly rods) where centering is nice but not critical. For the ferrules, I held them in a hexagonal 5C collet block and made 3 through cuts, rotating the block between cuts. For centering, I mounted a laser edge finder in the collet block and raised/lowered the knee to center the laser beam on the slitting saw (0.008" thick). I used the spread of the light on the arbor as a quide as well as on the cutter.

I'm interested in hearing about alterative/better methods.

 

[Jim F]

Touch off on the top and bottom, split the difference.

 

[RaisedByWolves]

For something simple like this I usually just touch off top/bottom and split the difference.

 

[jwmelvin]

If you have a DRO on z, you can center by contacting top and bottom of the saw blade (while spinning to include its axial runout). Without DRO could do the same just a little harder because of backlash.

 

[mattthemuppet2]

Touch off on the top, lower half the width of the cutter and zero. Then lower the tool by half the width of the part

 

[woodchucker]

Or, without a dro which makes backlash non existent you could measure the piece with a mic.
so if you have a knee mill touch the bottom then zero your dial. Then raise the mill to 1/2 the center
then raise it again to 1/2 the cutter width.

if you have a column type, you raise the head rather than the knee, since gravity removes the backlash if you are moving up.
you never want to change direction without taking out the backlash.. so you need to pass the mark, then move in your original direction.

 

[woodchucker]

BTW, I would never use a laser for pin point work. I find them not accurate enough.

 

[RaisedByWolves]

BTW, I would never use a laser for pin point work. I find them not accurate enough.

I was thinking the same.

 

[Canus]

If you are cutting the "slot" to insert a woodruff key into you will need to use a key cutting bit of the correct size for the key NOT a slitting saw. Center the bit as described above. I prefer touching off on the top of the shaft then raising the table 1/2 the shaft diameter plus 1/2 the cutter thickness. Machine to the proper depth. Machinery handbook will provide this dimension.

 

[RJSakowski]

I use the TTS system for tool holding in my mills so the tool offset is repeatable when removing and reinserting tools. I use a tenths reading digital dial indicator as a reference and measure tool height relative to my dial indicator with a digital height gage. The benefit of this is that I have a consistent tool offset relative to the dial indicator and I can use the dial indicator to find the surface of the part to sub thousandths accuracy. From there, I apply the tool offset, correct for the Woodruff keycutter width and diameter of the bar and I'm good to go.

Lacking the TTS system, I would touch off the cutter on top of the bar, using a piece of thin paper, correct for the paper thickness, the Woodruf key cutter width, and the diameter of the bar. This should get me to within a thousandth or two of where I need to be.