Rotary Table CNCing

[ptjw7uk]

Nice one Irving, problem I had was fitting a thrust bearing on the inside to take the trust in reverse so to speak. There is not a lot of room inside the unit but I managed to do it although I had to do some machining inside the block to make room for the thrust race.
Your diagram shows only one thrust race so OK in one direction only.

Peter

[John S]

Use an Oldham coupling, Lovejoy couplings don't take misalignment into account.

I have done one of the 4" tilting units, the cheap and nasty ones just to see if a type17 motor will run it, yes it does but only for positioning, not enough power to overcome cutting forces if you want to machine say an arc.

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[irving2008]

Use an Oldham coupling, Lovejoy couplings don't take misalignment into account.

I have done one of the 4" tilting units, the cheap and nasty ones just to see if a type17 motor will run it, yes it does but only for positioning, not enough power to overcome cutting forces if you want to machine say an arc.

.

John,

Where is the misalignment? using my proposed tube mounting approach everything is concentric. And I have several LC couplings going spare.

I am using a type 23 1Nm unit which I have here, but I could get a 1.85Nm type 23 from Zapp if needed. I measured the torque needed to turn the table and the 1Nm motor should be able to give about 5rpm for positioning and 1/2 of that for cutting, assuming alloy only (20N cutting forces as per other discussions on torque). My main interest is not cutting arcs but engraving handwheels and cutting gears...

[irving2008]

Yes I pulled the worm out and internally there is a cast iron to cast iron bearing. It would be possible to fit a thrust bearing in there but the problem is finding a small enough OD diameter with an ID of 10mm. Possible a needle thrust if i could find something small enough, but the smallest is 24mm OD, or 18mm as a ball thrust washer. Another option could be an oiliite washer maybe?

It really needs to be <15mm OD i.e. about the same dia as the worm gear, I think, because of the offset of the spindle. The alternative would be to bore out the base of the cavity just above the wormwheel to a diameter of about 20mm to allow the eccentric to rotate the thrust washer into when disengaging the drive. Not impossible to do, but tricky, and means stripping the rest of the table down.