Hi
The way I see the picture, you have quite a few microns of play only in
the roughness of the hole.
Using the screws that way amplifies the problem, as is pushes all the
error to one side.
I think the best option is to buy an elastic coupling. Ideally one that
fits both sizes, but just one and machining the other should work too.
But, if you want to do it in one piece. First, get as tight a fit as
possible, without removing the piece from the chuck. Drill 8.5 - 9 mm,
ream to 3/8'', expand half to 14 mm. Then either split it radially on
one side and add a couple of tangential screws (so that is closes on the
center, not one side), or put 3 screws at 120 deg on each shaft, and
adjust until removing the runout.
On 6/18/2021 18:49, John Dammeyer wrote:
This isn't as much a LinuxCNC question but more of an approach to how to
machine something.
The attached photo shows a coupler from a 3/8" encoder to 14mm Servo Motor so I can test on the bench the Pi4 closed loop encoder behavior.
This one didn't turn out very well. I drilled all the way through and then used a reamer to bring it to 3/8". It's a firm sliding fit on the encoder shaft. Without removing it from the chuck I then drilled halfway to 13mm and then used a 14mm reamer to bring it to size, testing with the motor shaft.
Problem was the reamer was slightly tapered at the front so it did a poor job. I finished it up with the boring tool but maybe a few thou too large. However the wobble seems much worse than that.
I'm thinking the better approach would be to drill all the way through undersize 3/8" and then drill half way with 13mm. Then only use the boring tool to bring the back half up to 3/8" and the front up to 14mm. This way if the initial hole wasn't concentric with rotation the boring tool would ensure it is.
Make sense? Or is there a better way?
Thanks
John
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