Making a Stainless Steel Watch Case and Back on the Shapeoko 3 (Start to Finish)

(Brian Renstrom) #101

rmwarren, I apologize, didn’t see those at first, thank you!

DanStory, yes, I am aware of the concerns, and you might be right. For some context, one thing I learned when machining stainless is that it’s best to avoid ramping an endmill – for internal pockets it’s better to pre-drill a hole for the endmill to drop into. I have used a regular hardware-store 1/8" drill bit to spot-drill hole centers in stainless for later drilling on a drill press, and the spotting actually worked quite well. Spot depth was .030", 10k RPM, I think the Z feed was 10 or 15 ipm. The problem with this approach is that I have to remove my workpiece from the CNC after spotting, drill the holes to final size manually, and put the workpiece back, which takes more time and introduces some inaccuracy. For “production” type projects this isn’t ideal – I’d rather have the CNC do as much as possible.

My goal was to have the machine peck-drill a 5/32" hole so that a 1/8" endmill can drop into it and bore it to final size, to avoid ramping. I see now that PreciseBits sells a [5/32 dia, 1/8 shank] drill bit that would be a better solution than the chuck. Or I could use a 1/8" drill and bore with a [3/32 dia, 1/8 shank] drill bit.

If I were to use the chuck, I do have a prop-balancer for R/C airplanes which I could use to balance the chuck if required. Shouldn’t be too hard. Runout is another matter though.

You edited your post to remove this part but I’d also add that I’m not using a Shapeoko, it’s actually a shapeoko-inspired machine I designed and built that uses acme leadscrew for all axes. I call it the Rigidoko. There is obviously still a risk of skipping steps, but it won’t skip teeth/threads.


Stainless knife blade milled on my machine