ELS on Mini-Lathe?

Another slight snag. I have the rotary encoder mounted on the main spindle, but I'm seeing a slight wobble in it as it turns. I had a feeling this would be an issue. I made a solid coupler, but I think I'm going to need a flexible shaft coupler of some type.

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I solved my issue with cutting the keyway for the pulley. I researched this a bit and decided to use the lathe to cut the keyway. At first, I thought I'd use a HSS bit, but I didn't have any 3 mm tooling over 1" long. So, I thought about using a 3 mm broach on the lathe. So, I ordered it from McMaster-Carr along with the appropriate 12 mm bore bushing. Not cheap!

Well, things started okay. I was able to use the tailstock with the Jacobs chuck to push the broach about half in before it didn't seem to want to go any further. I also tried the carriage, but it didn't want to move at all. Remember this is a 7X16 mini-lathe.

I decided to try using my huge woodworking vise. It worked beautifully! It had plenty of force to push the broach through. I used the lathe's 3-jaw chuck to hold the pulley. Near the end of the stroke, I used a 2X6 with a hole drilled in it to allow the broach to exit and not hit the vise's jaw. I know this is not the approved method and most machinist's would shudder, but it worked. It took a 10 second operation on an arbor press and made it into a 30-40 minute adventure! If I need to do this again, I will buy an arbor press!

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I made my keyway by first drilling two small holes on-center in the corners, then using a 1/8" end mill to connect them. The reasoning is that the corners serve no purpose so are "expendable."
 
devils4ever said:
Another slight snag. I have the rotary encoder mounted on the main spindle, but I'm seeing a slight wobble in it as it turns. I had a feeling this would be an issue. I made a solid coupler, but I think I'm going to need a flexible shaft coupler of some type.

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If you're going to keep the hard connection, a better way is to have the encoder free-floating on the shaft, and having the only connection to it being a radial.connection to keep it from spinning. Direct connections on spinning things never work for long.

[edit] I don't know why I didn't suggest one of the couplers, as suggested below, sigh. I would, however, suggest the helical-cut type instead of a plastic insert, though with so little needed torque, it probably doesn't matter.
 
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kb58 said:
I made my keyway by first drilling two small holes on-center in the corners, then using a 1/8" end mill to connect them. The reasoning is that the corners serve no purpose so are "expendable."
Click to expand...

I thought of doing that, but the pulley is 1" thick. I'm not sure a drill or end mill would stay true if I could find one that long.
 
I got the wobble out using this flexible shaft coupler from McMaster-Carr. It allows for angular and parallel shaft misalignment. Each piece is ordered separately, so I was able to get a 6 mm shaft diameter and a 12 mm shaft diameter. The center piece hub comes in different durometers for different applications. Not the cheapest solution, but probably the most precise.

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Here it is all mounted together.

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Weird, a coupler like that is the first/go to solution. I really didn't think it would allow for wobble. I assumed something was slightly misaligned? Nice!
 
Getting close to the finish line! I have the motor mounted. I made a slot in the two mounting points to allow belt tightening adjustments.

I need to do some test cuts, but it seems to work as expected. I still need to mount the steel electronics enclosure and LED display/switch box.

The second photo below show a plywood prototype I used to test my dimensions. Note this is the second iteration of the mount. The first one had a mounting standoff in way of the belt so I had to angle the motor mounting points.

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I'm working hard to stash everything where it can't be seen...not a lot of room on the lathe to do that. Hopefully in the next week the motor and servo will have their homes and I'm running.
 
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