Thinking about doing a practice block. Recommendations?
 

I got some spare time for the first time this semester. The local machine shop has tons of scrap aluminium (enough to make dozens of blocks) and i can use as much as i like. I'd like to practice milling a block. I've got some fairly small endmills (down to 1/4 inch IIRC), every size tap and tons of lucite. What should i start with? I'm thinking a rotor style block with a gasket and lucite top. Doable with very little experience and 1/4 inch mill bit?

mIght try a roughing mill bit and to add a lot more surface area per pin.

1/4" seems a bit large, especially for the channels between the holes. It would mean either ending up with very few pins, and/or very tiny ones with most of the block space being water passage.

I would suggest a 1/8" or so bit instead, but either be very careful to use shallow cuts and slow feeds, or plan on breaking a few bits. (I went through about 8 bits making two blocks in Cu) Coolant will help.

What I did was to make a 'gallery' at each end with a grid of 1/8" passages on 1/4" centers (leaving 1/8" pins) connecting them. The grid lines were at a 45* angle to the galleries, so there was no 'straight line' path through the block, but rather the coolant would be forced to follow a zig-zag path, with a potential collision and resulting turbulence at each intersection.

I crudely flow tested the two blocks with a 'bucket test' and got approx 3GPM in series, or 5GPM in parallel using an Iwaki MD-20RT pump (8GPM into 14' head specs)

Gooserider

For a rotor type block you will want 1/4" DRILL bit (3/16" might be better), and a 1/16" end mill to connect the grid. Don't try and use the endmill for plunge drilling unless it is a ball nosed one. Once you get the holes drilled you can then plung the endmill in the drilled holes to flatten the bottom of the holes. Not sure if that would help or not though.

If 1/4" is the smallest you got and you want to mill something then try a maze design or something.