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Archive for March 9th, 2009

Machining a Shoulder Ring in a Hole

Step bit making an annular ring

Step bit making an annular ring

I needed a shoulder around the inside of a hole, upon which to mount a big fat 10-mm white LED. The intent was that the LED leads go through the hole, the edge of its case sits on the shoulder, and a blob of hot-melt glue (epoxy for the final version) holds everything in place.

I was all set for some CNC milling when it occurred to me that there was an easier way.

The bottom flange on the LED case was scant of 11 mm, so a 13/32″ bit would be just just slightly too small and a 7/16″ bit would be just slightly too large. One of my step bits has 1/32″ increments in that range, sooo

I grabbed the part in a Sherline 3-jaw chuck (I’d just drilled & tapped the three radial holes using that chuck), centered it in the drill press using a 5/16″ drill that just fit the existing center hole, crunched the chuck (lightly!) in the vise with the hole over the gap in the middle of the vise body (thus leaving room for the step bit), and drilled the hole 7/16″ about 1 mm down.

(It’s not that I’ve never drilled right into the vise body, but I try to avoid doing that sort of thing more often than absolutely necessary.)

The LED flange sat on 13/32″ annulus like I’d bored it to the exact measurements, with the leads passing through the hole as if I intended it to be that way.

It doesn’t always work out this neatly…

The Sherline chuck is resting on a pair of 5/16″ lathe bits that hold it up off the vise body, because its threaded hub isn’t quite large enough to make a stable base. Similarly, I used a pair of 1/4″ bits to space that plastic ring up from the chuck and get it level, but removed them lest I chew up the step bit. Yes, I took the drilling slow & easy.

Those little Sherline chucks come in handy around the shop, not just on the Sherline mill, for little jobs like this!

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