Tuesday, May 24, 2011

My first completely useful casting!

I've been casting aluminum for a while, but haven't made a whole lot of actually useful things.  Recently, Chief Tard asked if I could copy a latch handle from his snow machine, but put a hex opening where his has a splined opening.  This allows him to use the latch pieces from a different year to repair his machine.

The handle was cast using my new oil-bonded sand.  It came out awesome.  It even has the original part numbers on it!  I just taped up the splined hole when I made the mold, so it was completely solid with no hole when I cast it.

Making the hex hole was the difficult part.  I don't have a rotary broach, so I made a hand tool to do the job.
I made the tool from W-1 drill rod, using my CNC machine to create the hex shape.  Then I used a ball end mill to "cup" the center of the tool.  This puts enough of an edge on the corners that they will cut.  Then I heated it red hot and quenched it in water to harden it.

I drilled a small hole all the way through the handle, then a larger 5/16" hole (the hex is 5/16" across flats) most of the way through. Then I used a hammer and tapped the tool into the hole.  The above photo is just after I started and it shows how the tool only cuts the sharp corners; the chips are visible.

Here is the finished hex hole.  This fits on a hex shaft and there is a screw that goes on the other side of the handle to hold it in place.

Here's a photo of the handle and the tool.  The handle was cleaned up with a grinder and wire wheel, and should fit nicely on the snow machine.

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