Raising a recessed rotary axis

I recess mounted my rotary axis to allow max workpiece diameter. If I raised the rotary axis by 0.8", it looks like I could gain 2+ inches in workpiece length. Has anyone tried or considered this?

I believe there is different mounting hardware for table top VS recessed mounting.

You might want to check here to see if you have all of the hardware you need:


The table top mount runs front-to-back across the frame and has a lower workpiece diameter capacity. I’m interested in a custom change, raising the recessed mount in place just enough to slide the motor back over the dust cover. I hope this would maintain the diameter capacity of the recessed mount while adding a small amount to the length capacity. The table top mounting hardware doesn’t look helpful for this.

The 40-8020 and 40-4020 extrusions are the right thickness for spacers. The slot is only on one side, but I could drill holes through it and get longer bolts. Am I overlooking anything obvious, or should I give it a go?

Will that make it too high so that your Z axis can’t go high enough for the larger diameter you can now mount? I can’t get to my machine right now to see, but I have the 12" axis so mine would probably be ok anyway.

I can’t see a reason why it wouldn’t work… You’ll be raising it up a little so you’ll lose a little Z clearance

Main thing is that you want to keep it level, and our rotary utility should still work to help you get it aligned.

You might not need any new 8020, I bet you could make some spacers to raise it up on it’s existing mounts…

Good question, I hadn’t thought about upward clearance.

I have an 8" Z-axis and gantry. It has 8 3/8" clearance between the crossbeams and the gantry’s lowest point. The recessed rotary axis center is 1 1/4" above the crossbeam tops. Raising it by 0.8" would still leave more than 6" between the axis center and the gantry, so that part wouldn’t be an issue. The mount position would still be 2 3/8" below the table top mount position.

Long bits might require attention. The gain in length would be worth that trade.

True. I could get longer bolts, and I have some acrylic sheet that could make a stable spacer. Anything else cheap and machinable? If that doesn’t work, the 8020 spacers would be about $40.

If it were me I’d just machine up some spacers out of some Baltic Birch scraps. That stuff is very stable considering it’s wood. Heck some MDF would be fine for a test too.

For bolts they are pretty standard metric threads (can’t remember the size off the top of my head) but If you have a good hardware store close by I bet you could find what you need.

If it all works maybe grab some aluminum bar stock and machine up some nice spacers.