Saturday, 24 February 2018

Group cap recap

The group cap has been a tail of (minor) woe for a while now.



I was all happy when I got the first batch out of the box what-seems-like-oh-so-long-along-now. Until that is, I put them on top of the group and discovered that the color of the chrome didn't match. That micro tragedy was joined by a second, rather more important problem: like, ya know, it don't fit! Seems like someone can't read their own writing: I made a transcription error when I was making the drawing for the part and the slot for the lever is 22mm wide instead of 32mm!

The first problem is easy to remedy with some sandblasting and a trip to the chrome store. The second one requires some slightly stronger medicine. 

This cap was sandblasted down to at least the copper layer under the chrome. The 1/4" endmill is just long enough to reach the bottom of the curve at the perimeter of the cap - which is a bit of luck as otherwise this would be a bit more tricky to CNC. 



The 1/4" bit leaves the appropriate radius in the corners of the slot.



The other half of the slot has to be machined with the chuck axis parallel to the table. This setup required a little bit of head scratching and some laaaaaarge clamps.



This isn't the stiffest of setups, so light cuts are in order.


All done - except for deburring (and sandblasting and re-chroming, (very small sigh)). 


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